Human Swine Flu Infection - California & Texas First Report April 21, 2009

[Laidback Al]

Swine flu cases in Calif. worry health officials 44 minutes ago

ATLANTA (AP) — Health officials have diagnosed a unique type of swine flu in two California children, but it's unclear whether many people will be susceptible to the infection.

The two children were diagnosed last week. One was a 10-year-old boy in San Diego County, and the other a 9-year-old girl in neighboring Imperial County. Both recovered.

The U.S. Centers for Disease Control and Prevention alerted doctors Tuesday, but said there's no reason for the public to take unusual measures.
The virus is resistant to two common antiviral medications, and health officials think the seasonal flu vaccine may not protect against it.


http://www.google.com/hostednews/ap/...MM_EQD97N164G2

[sharon sanders]

CDC - Interim Guidance on Infection Control and Antiviral Recommendations for Patients with Confirmed or Suspected Swine Influenza A Virus Infection


http://www.flutrackers.com/forum/showthread.php?t=99765

[sharon sanders]

from MMWR - April 17th Issue

"...Novel Influenza A Viruses

A case of human infection with a novel influenza A virus was reported by the Iowa Department of Public Health during the week ending February 28, 2009. A male aged 3 years was infected with a swine influenza A (H1N1) virus. An investigation revealed that the child had close contact with ill pigs. The child has fully recovered from the illness, and no additional cases were identified among the child's contacts or other persons exposed to the ill pigs. This is the third human infection with swine influenza virus identified in the United States this influenza season. None of the cases were related to occupation. The other two human infections with swine influenza identified during the 2008--09 influenza season occurred in a person aged 14 years from Texas and a person aged 19 years from South Dakota..."


http://www.flutrackers.com/forum/sho...087#post220087

[Giuseppe Michieli]

New type of flu found in two U.S. children: CDC - Reuters

New type of flu found in two U.S. children: CDC

Tue Apr 21, 2009 7:43pm BST
WASHINGTON (Reuters) -

A new type of swine flu has infected at least two children in California and, while they have recovered, U.S. health officials said on Tuesday they were concerned.


The influenza strain is an H1N1, the same family as one of the seasonal flu viruses now circulating. But genetically, it resembles a virus found in pigs and not in people, officials at the U.S. Centers for Disease Control and Prevention said.

CDC experts described two of the cases in a special notice to doctors and public health officials.

They say it is possible the children were infected by other people and not by pigs, and said they have consulted with officials in Canada, Mexico and at the World Health Organization although there is no evidence that this new virus is circulating widely.

(Reporting by Maggie Fox; Editing by Julie Steenhuysen and Bill Trott)
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New type of flu found in two U.S. children: CDC | Science & Health | Reuters

[sharon sanders]

Key Facts about Swine Influenza (Swine Flu)

What is Swine Influenza?

Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza that regularly cause outbreaks of influenza among pigs. Swine flu viruses cause high levels of illness and low death rates among pigs. Swine influenza viruses may circulate in swine throughout the year, but most outbreaks among swine herds occur during the late fall and winter months similar to humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.

How common is swine flu among pigs?

H1N1 and H3N2 swine flu viruses are endemic among pig populations in the United States and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months (late fall and winter) and sometimes with the introduction of new pigs into susceptible herds. Studies have shown that the swine flu H1N1 is common throughout pig populations worldwide, with 25 percent of animals showing antibody evidence of infection. In the U.S. studies have shown that 30 percent of the pig population in the U.S. has antibody evidence of having had H1N1 infection. More specifically, 51 percent of pigs in the north-central U.S. have been shown to have antibody evidence of infection with swine H1N1. Human infections with swine flu H1N1 viruses are rare. There is currently no way to differentiate antibody produced in response to flu vaccination in pigs from antibody made in response to pig infections with swine H1N1 influenza.

While H1N1 swine viruses have been known to circulate among pig populations since at least 1930, H3N2 influenza viruses did not begin circulating among US pigs until 1998. The H3N2 viruses initially were introduced into the pig population from humans. The current swine flu H3N2 viruses are closely related to human H3N2 viruses.

Can humans catch swine flu?

Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. In the past several years, on average CDC has received about one influenza virus isolate from a human that tests positive for swine flu each year. Most commonly, these cases occur in persons with direct exposure to pigs (workers in the swine industry, for example). In addition, there have been rare documented cases of one person spreading swine flu to others. For example, an outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.

How does swine flu spread?

• Pigs infected with influenza virus have a runny nose, lethargy, cough and decreased appetite. The virus likely spreads from pig to pig through contact with infected mucous secretions. (When the pigs are really sick, their mucus carries high levels of virus.)
• Strains of swine flu virus can also be directly transmissible to humans. Most human infections have occurred following direct contact with infected pigs. However, there has been at least one documented case of human-to-human transmission of swine flu.

What do we know about human-to-human spread of swine flu?

In September 1988, a previously healthy 32-year-old pregnant woman was hospitalized for pneumonia and died 8 days later. A swine H1N1 flu virus was detected. Four days before getting sick, the patient visited a county fair swine exhibition where there was widespread influenza-like illness among the swine.

In follow-up studies, 76% of swine exhibitors tested had antibody evidence of swine flu infection but no serious illnesses were detected among this group. Additional studies suggest that one to three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.

What other examples of swine flu outbreaks are there?

Probably most well known is an outbreak of swine flu among soldiers in Fort Dix, New Jersey in 1976. The virus caused disease with x-ray evidence of pneumonia in at least 4 soldiers and 1 death; all of these patients had previously been healthy. The virus was transmitted to close contacts in a basic training environment, with limited transmission outside the basic training group. The virus is thought to have circulated for a month and disappeared. The source of the virus, the exact time of its introduction into Fort Dix, and factors limiting its spread and duration are unknown. The Fort Dix outbreak may have been an animal anomaly caused by introduction of an animal virus into a stressed human population in close contact in crowded facilities during the winter. The swine influenza A virus collected from a Fort Dix soldier was named A/New Jersey/76 (Hsw1N1).

How many swine flu viruses are there?

Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine flu viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H3N2 and H1N1 viruses.

Is the H1N1 swine flu virus the same as human H1N1 viruses?

No. The H1N1 swine flu viruses are antigenically very different from human H1N1 viruses.

Is there a vaccine for swine flu?

Vaccines are available to be given to pigs to prevent swine influenza. There is no vaccine to protect humans from swine flu. The seasonal influenza vaccine will likely help provide partial protection against swine H3N2, but not swine H1N1 viruses.

What are the public health implications of human infections with swine influenza viruses?

Human infections with animal influenza A viruses against which the human population has little immunity should be investigated to determine the source of infection, and the extent of spread and evidence of human to human transmission. Influenza A viruses new to the human population that are able to efficiently transmit from person to person and cause illness may represent a pandemic threat.

Although immunity to swine H1N1 viruses is low in the human population, a high proportion of persons occupationally exposed to pigs (such as pig farmers or pig veterinarians) have been shown in several studies to have antibody evidence of prior swine H1N1 flu infection. And, for swine H1N1 viruses, only rare person to person transmission has been documented in the past. Thus, human infections with swine H1N1 viruses should be investigated particularly when they are detected among non-occupationally exposed persons to ensure that human to human transmission is not occurring and to monitor for changes in circulating viruses and the emergence of novel viruses.


Because most persons have some antibody to influenza H3N2 viruses since H3N2 viruses occur commonly in humans and because the swine and human H3N2 viruses are similar, swine H3N2 virus infections in humans would not represent a possible pandemic threat.



http://www.cdc.gov/flu/swine/key_facts.htm

[Giuseppe Michieli]

Reuters AlertNet - New type of flu affects a few US children - CDC

New type of flu affects a few US children - CDC

21 Apr 2009 19:02:26 GMT
Source: Reuters

*New type of swine flu never seen before
*Flu may have spread person to person

By Maggie Fox, Health and Science Editor
WASHINGTON, April 21 (Reuters) -

A new type of swine flu has infected at least two children in California, and while both have recovered, U.S. health officials said on Tuesday they were concerned.


They say it is possible the children were infected by other people and not by pigs, and said they have consulted with officials in Canada, Mexico and at the World Health Organization although there is no evidence that the new virus is circulating widely.

In a special alert, the CDC asked doctors in California's San Diego and Imperial counties, on the border with Mexico, to test anyone with flu-like symptoms and send the samples in for testing.

"Both of these kids came to our attention because they were seen in clinics which do routine surveillance for influenza infections," the CDC's Dr Lyn Finelli told reporters in a telephone briefing.

Neither child, a 10-year-old boy and a 9-year-old girl, had especially severe symptoms, although the girl had had a fever of 104 degrees, Finelli said.

The influenza strain is an H1N1, the same family as one of the seasonal flu viruses now circulating. But it genetically resembles a virus found in pigs and not in people, officials at the U.S. Centers for Disease Control and Prevention said.

"The viruses from the two cases are closely related genetically, resistant to (the antiviral drugs) amantadine and rimantadine, and contain a unique combination of gene segments that previously had not been reported among swine or human influenza viruses in the United States or elsewhere," they wrote.

"Neither child had known contact with pigs. The source of infection is unknown," they added. "The lack of known exposure to pigs in the two cases increases the possibility that human-to-human transmission of this new influenza virus has occurred."

In the past two or so years, Finelli said, 12 known cases of infection with swine flu have been reported but 11 of them followed known contact with pigs.

People who had contact with the children were being questioned by CDC investigators and tested if they remember having been sick recently. The boy flew to Texas with his brother and is still there, the officials added.

Blood tests may show if people were infected in the past with the same virus.

The virus is usually fairly mild but it still kills between 250,000 and 500,000 people in an average year. And every few decades, a completely new strain pops up and it can cause a pandemic, a global epidemic that kills many more than usual.

CDC officials said that they do not believe these two cases represent the beginning of such a pandemic.

(Reporting by Maggie Fox, editing by Patricia Zengerle)
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Reuters AlertNet - New type of flu affects a few US children - CDC

[Shiloh]

Source: http://www.google.com/hostednews/ap/...MM_EQD97N25U80

Swine flu cases in Calif. worry health officials

ATLANTA (AP) — Health officials alerted doctors Tuesday to a unique type of swine flu diagnosed in two California children, but it's unclear whether many people will be susceptible to the infection.

The children were diagnosed last week. One was a 10-year-old boy in San Diego County, and the other a 9-year-old girl in neighboring Imperial County. Both recovered.

U.S. Centers for Disease Control and Prevention officials said there's no reason for the public to take unusual measures against it.

"CDC is concerned, but that's our job," said CDC spokesman Tom Skinner.

Health officials have long feared the emergence of a deadly form of flu. They have not noted a spike in flu cases or a rash of severe illnesses. But they are continuing to investigate the genetics of the virus and track down and test people who may have been in contact with the children.

Both children became sick in late March and experienced fever and cough. The boy also vomited.

The two had not been in contact with each other, CDC officials said.

The boy's mother and brother also had a flu-like illness recently, as did a brother and a cousin of the girl. None of those relatives were tested for flu at the time of their illness.

The San Diego County boy and his 8-year-old brother flew from California to Dallas in early April and are currently with relatives in Texas. Health officials also are trying to contact the plane's flight crew and two children who sat near the boys, CDC officials said.

In the past, CDC received reports of approximately one human swine influenza virus infection every one or two years. But more than a dozen cases of human infection with swine influenza have been reported since late 2005.

Most cases occur in people who were exposed to pigs. Neither child had touched a pig, according to their families, although the girl had been at an agricultural fair four weeks before she got sick.

The jump in cases in the past few years could be because of technological improvements and expansion of public health laboratories, which have improved testing capacity. But genetic mutations could also play a role.

The new flu contains a unique combination of gene segments that have not been seen in swine or human flu viruses before, CDC officials said.

Early tests indicate this type of flu is resistant to amantadine and rimantadine, two common antiviral medications. It is not unique in that respect — a more common virus that's been infecting people this flu season also is resistant to those drugs.

Health officials think the current seasonal flu vaccine may not protect against it.

Swine flu is an infamous disease in public health circles. In 1976, health officials were frightened by unusual cases of swine flu in soldiers at Fort Dix, N.J. The virus appeared to be similar to a deadly flu that killed millions around the world in 1918 and 1919.

Federal officials vaccinated 40 million Americans during a national campaign. The pandemic never materialized, but thousands who got the shots filed injury claims, saying they suffered a paralyzing condition and other side effects from the vaccinations.

The government is more sophisticated now in how it diagnoses and tracks diseases, said Dr. Lyn Finelli, a CDC epidemiologist.

[sharon sanders]

"..The new flu contains a unique combination of gene segments that have not been seen in swine or human flu viruses before, CDC officials said.

Early tests indicate this type of flu is resistant to amantadine and rimantadine, two common antiviral medications. It is not unique in that respect — a more common virus that's been infecting people this flu season also is resistant to those drugs.

Health officials think the current seasonal flu vaccine may not protect against it..."

[Giuseppe Michieli]

The Canadian Press: Unrelated cases of swine flu in humans have U.S. officials on alert

Unrelated cases of swine flu in humans have U.S. officials on alert

U.S. authorities are investigating two cases of swine flu in unrelated children in California.


Discovery of the two cases, in children who apparently had no contact with pigs or with each other, is raising questions about whether swine flu viruses are circulating there.

Officials of the U.S. Centers for Disease Control say they have informed the World Health Organization of the cases and the investigation that is underway.

The 10-year-old boy and nine-year-old girl were infected with influenza A swine viruses of the H1N1 subtype.

Officials say it's not yet clear whether a swine H1N1 virus could trigger a human pandemic, because there is a lot of immunity in humans to human H1N1 viruses.

A senior official with the WHO says the organization is following the situation closely but there is no need to change the pandemic alert level at this point.
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The Canadian Press: Unrelated cases of swine flu in humans have U.S. officials on alert

[Giuseppe Michieli]

Reuters AlertNet - US officials track new flu strain

US officials track new flu strain

21 Apr 2009 20:20:38 GMT
Source: Reuters

* New type of swine flu never seen before
* Flu may have spread person to person

(Adds quotes, details, paragraphs 6, 8, background paras 14-16)

By Maggie Fox, Health and Science Editor
WASHINGTON, April 21 (Reuters) -

A new type of swine flu has infected at least two children in California and while both have recovered, U.S. health officials said on Tuesday they were looking for more cases.


They say it is possible the children were infected by other people and not by pigs, and said they have consulted with officials in Canada, Mexico and at the World Health Organization although there is no evidence that the new virus is circulating widely.

In a special alert, the CDC asked doctors in California's San Diego and Imperial counties, on the border with Mexico, to test anyone with flu-like symptoms and send the samples in for testing.

"Both of these kids came to our attention because they were seen in clinics which do routine surveillance for influenza infections," the CDC's Dr. Lyn Finelli told reporters in a telephone briefing.

Neither child, a 10-year-old boy and a 9-year-old girl, had especially severe symptoms, although the girl had had a fever of 104 degrees, Finelli said.

"We are not making the assumption that there are widespread infections out there and there is not any action that the public should take right now," Finelli said.


The influenza strain is an H1N1, the same family as one of the seasonal flu viruses now circulating. But it genetically resembles a virus found in pigs and not in people, officials at the U.S. Centers for Disease Control and Prevention said.

It has never been seen before, the CDC said.

"Neither child had known contact with pigs. The source of infection is unknown," they added. "The lack of known exposure to pigs in the two cases increases the possibility that human-to-human transmission of this new influenza virus has occurred."

CONTACT TRACING
In the past two or so years, Finelli said, 12 known cases of infection with swine flu have been reported but 11 of them followed known contact with pigs.

People were near the children were being questioned by CDC investigators and tested if they remember having been sick recently. The boy flew to Texas with his brother and is still there, the officials added.

Blood tests may show if people were infected in the past with the same virus.

The virus is usually fairly mild but it still kills between 250,000 and 500,000 people in an average year. And every few decades, a completely new strain pops up and it can cause a pandemic, a global epidemic that kills many more than usual.

Flu experts are afraid a pandemic could come at any time and are monitoring for new strains. One big fear is that the H5N1 avian flu virus now mostly affecting flocks in Asia, the Middle East, Europe and Africa might mutate into a form that could cause a pandemic.

It currently only rarely infects people but has killed 257 out of 420 infected in 15 countries since 2003, according to the World Health Organization.

CDC officials said that they do not believe these two cases represent the beginning of such a pandemic.

(Reporting by Maggie Fox,)
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Reuters AlertNet - US officials track new flu strain

[HenryN]

HA, NA, and MP sequences have been released at GISAID for one of the California isolates.

[sharon sanders]

from a friend of FT -

April 21, 2009 / 58 (Dispatch);1-3

Swine Influenza A (H1N1) Infection in Two Children --- Southern California, March--April 2009 On April 17, 2009, CDC determined that two cases of febrile respiratory illness occurring in children who resided in adjacent counties in southern California were caused by infection with a swine influenza A (H1N1) virus. The viruses from the two cases are closely related genetically, resistant to amantadine and rimantadine, and contain a unique combination of gene segments that previously has not been reported among swine or human influenza viruses in the United States or elsewhere. Neither child had contact with pigs; the source of the infection is unknown. Investigations to identify the source of infection and to determine whether additional persons have been ill from infection with similar swine influenza viruses are ongoing. This report briefly describes the two cases and the investigations currently under way. Although this is not a new subtype of influenza A in humans, concern exists that this new strain of swine influenza A (H1N1) is substantially different from human influenza A (H1N1) viruses, that a large proportion of the population might be susceptible to infection, and that the seasonal influenza vaccine H1N1 strain might not provide protection. The lack of known exposure to pigs in the two cases increases the possibility that human-to-human transmission of this new influenza virus has occurred. Clinicians should consider animal as well as seasonal influenza virus infections in their differential diagnosis of patients who have febrile respiratory illness and who 1) live in San Diego and Imperial counties or 2) traveled to these counties or were in contact with ill persons from these counties in the 7 days preceding their illness onset, or 3) had recent exposure to pigs. Clinicians who suspect swine influenza virus infections in a patient should obtain a respiratory specimen and contact their state or local health department to facilitate testing at a state public health laboratory. Case Reports Patient A. On April 13, 2009, CDC was notified of a case of respiratory illness in a boy aged 10 years who lives in San Diego County, California. The patient had onset of fever, cough, and vomiting on March 30, 2009. He was taken to an outpatient clinic, and a nasopharyngeal swab was collected for testing as part of a clinical study. The boy received symptomatic treatment, and all his symptoms resolved uneventfully within approximately 1 week. The child had not received influenza vaccine during this influenza season. Initial testing at the clinic using an investigational diagnostic device identified an influenza A virus, but the test was negative for human influenza subtypes H1N1, H3N2, and H5N1. The San Diego County Health Department was notified, and per protocol, the specimen was sent for further confirmatory testing to reference laboratories, where the sample was verified to be an unsubtypable influenza A strain. On April 14, 2009, CDC received clinical specimens and determined that the virus was swine influenza A (H1N1). The boy and his family reported that the child had had no exposure to pigs. Investigation of potential animal exposures among the boy's contacts is continuing. The patient's mother had respiratory symptoms without fever in the first few days of April 2009, and a brother aged 8 years had a respiratory illness 2 weeks before illness onset in the patient and had a second illness with cough, fever, and rhinorrhea on April 11, 2009. However, no respiratory specimens were collected from either the mother or brother during their acute illnesses. Public health officials are conducting case and contact investigations to determine whether illness has occurred among other relatives and contacts in California, and during the family's travel to Texas on April 3, 2009. Patient B. CDC received an influenza specimen on April 17, 2009, that had been forwarded as an unsubtypable influenza A virus from the Naval Health Research Center in San Diego, California. CDC identified this specimen as a swine influenza A (H1N1) virus on April 17, 2009, and notified the California Department of Public Health. The source of the specimen, patient B, is a girl aged 9 years who resides in Imperial County, California, adjacent to San Diego County. On March 28, 2009, she had onset of cough and fever (104.3°F [40.2°C]). She was taken to an outpatient facility that was participating in an influenza surveillance project, treated with amoxicillin/clavulanate potassium and an antihistamine, and has since recovered uneventfully. The child had not received influenza vaccine during this influenza season. The patient and her parents reported no exposure to pigs, although the girl did attend an agricultural fair where pigs were exhibited approximately 4 weeks before illness onset. She reported that she did not see pigs at the fair and went only to the amusement section of the fair. The Imperial County Public Health Department and the California Department of Public Health are now conducting an investigation to determine possible sources of infection and to identify any additional human cases. The patient's brother aged 13 years had influenza-like symptoms on April 1, 2009, and a male cousin aged 13 years living in the home had influenza-like symptoms on March 25, 2009, 3 days before onset of the patient's symptoms. The brother and cousin were not tested for influenza at the time of their illnesses. Epidemiologic and Laboratory Investigations As of April 21, 2009, no epidemiologic link between patients A and B had been identified, and no additional cases of infection with the identified strain of swine influenza A (H1N1) had been identified. Surveillance data from Imperial and San Diego counties, and from California overall, showed declining influenza activity at the time of the two patients' illnesses. Case and contact investigations by the county and state departments of health in California and Texas are ongoing. Enhanced surveillance for possible additional cases is being implemented in the area. Preliminary genetic characterization of the influenza viruses has identified them as swine influenza A (H1N1) viruses. The viruses are similar to each other, and the majority of their genes, including the hemagglutinin (HA) gene, are similar to those of swine influenza viruses that have circulated among U.S. pigs since approximately 1999; however, two genes coding for the neuraminidase (NA) and matrix (M) proteins are similar to corresponding genes of swine influenza viruses of the Eurasian lineage (1). This particular genetic combination of swine influenza virus segments has not been recognized previously among swine or human isolates in the United States, or elsewhere based on analyses of influenza genomic sequences available on GenBank.* Viruses with this combination of genes are not known to be circulating among swine in the United States; however, no formal national surveillance system exists to determine what viruses are prevalent in the U.S. swine population. Recent collaboration between the U.S. Department of Agriculture and CDC has led to development of a pilot swine influenza virus surveillance program to better understand the epidemiology and ecology of swine influenza virus infections in swine and humans. The viruses in these two patients demonstrate antiviral resistance to amantadine and rimantadine, and testing to determine susceptibility to the neuraminidase inhibitor drugs oseltamivir and zanamivir is under way. Because these viruses carry a unique combination of genes, no information currently is available regarding the efficiency of transmission in swine or in humans. Investigations to understand transmission of this virus are ongoing. Reported by: M Ginsberg, MD, J Hopkins, MPH, A Maroufi, MPH, G Dunne, DVM, DR Sunega, J Giessick, P McVay, MD, San Diego County Health and Human Svcs; K Lopez, MD, P Kriner, MPH, K Lopez, S Munday, MD, Imperial County Public Health Dept; K Harriman, PhD, B Sun, DVM, G Chavez, MD, D Hatch, MD, R Schechter, MD, D Vugia, MD, J Louie, MD, California Dept of Public Health. W Chung, MD, Dallas County Health and Human Svcs; N Pascoe, S Penfield, MD, J Zoretic, MD, V Fonseca, MD, Texas Dept of State Health Svcs. P Blair, PhD, D Faix, PhD, Naval Health Research Center; J Tueller, MD, Navy Medical Center, San Diego, California. T Gomez, DVM, Animal and Plant Health Inspection Svc, US Dept of Agriculture. F Averhoff, MD, F Alavrado-Ramy, MD, S Waterman, MD, J Neatherlin, MPH, Div of Global Migration and Quarantine; L Finelli, DrPH, S Jain, MD, L Brammer, MPH, J Bresee, MD, C Bridges, MD, S Doshi, MD, R Donis, PhD, R Garten, PhD, J Katz, PhD, S Klimov, PhD, D Jernigan, MD, S Lindstrom, PhD, B Shu, MD, T Uyeki, MD, X Xu, MD, N Cox, PhD, Influenza Div, National Center for Infectious and Respiratory Diseases, CDC. Editorial Note: In the past, CDC has received reports of approximately one human swine influenza virus infection every 1--2 years in the United States (2,3). However, during December 2005--January 2009, 12 cases of human infection with swine influenza were reported; five of these 12 cases occurred in patients who had direct exposure to pigs, six in patients reported being near pigs, and the exposure in one case was unknown (1,4,5). In the United States, novel influenza A virus infections in humans, including swine influenza infections, have been nationally notifiable conditions since 2007. The recent increased reporting might be, in part, a result of increased influenza testing capabilities in public health laboratories, but genetic changes in swine influenza viruses and other factors also might be a factor (1,4,5). Although the vast majority of human infections with animal influenza viruses do not result in human-to-human transmission (2,3), each case should be fully investigated to be certain that such viruses are not spreading among humans and to limit further exposure of humans to infected animals, if infected animals are identified. Such investigations should include close collaboration between state and local public health officials with animal health officials. The lack of known exposure to pigs in the two cases described in this report increases the possibility that human-to-human transmission of this new influenza virus has occurred. Clinicians should consider animal as well as seasonal influenza virus infections in the differential diagnosis of patients with febrile respiratory illness who live in San Diego and Imperial counties or have traveled to these areas or been in contact with ill persons from these areas in the 7 days before their illness onset. In addition, clinicians should consider animal influenza infections among persons with febrile respiratory illness who have been near pigs, such as attending fairs or other places where pigs might be displayed. Clinicians who suspect swine influenza virus infections in humans should obtain a nasopharyngeal swab from the patient, place the swab in a viral transport medium, and contact their state or local health department to facilitate transport and timely diagnosis at a state public health laboratory. CDC requests that state public health laboratories send all influenza A specimens that cannot be subtyped to the CDC, Influenza Division, Virus Surveillance and Diagnostics Branch Laboratory. Interim guidance on infection control, treatment, and chemoprophylaxis for swine influenza is available at http://www.cdc.gov/flu/swine/recommendations.htm. Additional information about swine influenza is available at http://www.cdc.gov/flu/swine/index.htm. References Vincent AL, Ma W, Lager KM, Janke BH, Richt JA. Swine influenza viruses: a North American perspective. Adv Virus Res 2008;72:127--54. Myers KP, Olsen CW, Gray GC. Cases of swine influenza in humans: a review of the literature. Clin Infect Dis 2007;44:1084--8. Wells DL, Hopfensperger DJ, Arden NH, et al. Swine influenza virus infections. Transmission from ill pigs to humans at a Wisconsin agricultural fair and subsequent probable person-to-person transmission. JAMA 1991;265:478--81. Vincent AL, Swenson SL, Lager KM, Gauger PC, Loiacono C, Zhang Y. Characterization of an influenza A virus isolated from pigs during an outbreak of respiratory disease in swine and people during a county fair in the United States. Vet Microbiol 2009;online publication ahead of print. Newman AP, Reisdorf E, Beinemann J, et al. Human case of swine influenza A (H1N1) triple reassortant virus infection, Wisconsin. Emerg Infect Dis 2008;14:1470--2. * Available at http://www.ncbi.nlm.nih.gov/Genbank.

[HenryN]

A/California/04/2009

is at GISAID. I do not see it at Genbank.

[HenryN]

HA is North American swine
NA is European swine

[HenryN]

Scientists Studying 2 Cases of Unknown Swine Flu Strain(Washn)

4/21/2009, 6:39 p.m. ET David Brown The Associated Press

(AP) — WASHINGTON ? Public health authorities are investigating two highly unusual cases of a previously unknown strain of swine flu that occurred in the San Diego area late last month.
The cases occurred almost simultaneously in children who had no contact with pigs or each other, a scenario that raised the possibility the illnesses might be the sign of an emerging pandemic strain of influenza.
More than 50 scientists and epidemiologists at the Centers for Disease Control and Prevention in Atlanta are studying the strain, and dozens of public health investigators in Southern California are looking for more cases among the those who had contact with the children.
"While we have a low index of suspicion that this is a pandemic, we're being very careful in our investigation to rule out every possibility," said Lyn Finelli, an epidemiologist in CDC's influenza division.
Neither of the children ? a 10-year-old boy in San Diego County and a 9-year-old girl in Imperial County, just to the east ? was seriously ill. The cases were detected because both were treated at clinics that took nose or throat swabs looking for influenza and passed the samples on to health department labs when they could not identify the strains they found.
"It was a very fortunate lightning strike," Finelli said Tuesday.
Both children have recovered. The San Diego boy, however, took an airplane trip to Texas with his younger brother while at the tail-end of his illness before it was know he had an unusual strain of flu. Health officials in the Dallas area are looking for cases there, as well as among airline employees who assisted the two children, who traveled as "unaccompanied minors."
Public health officials in the two California counties, which both border Mexico, are urging physicians and hospitals to look carefully for cases of flu and report any to local health departments.
Flu season, which officially ended this month, was mild this year. But Imperial County's health officer, Stephen Munday, said his jurisdiction saw a blip of cases late in March, although not enough to qualify as an outbreak. Whether any other cases involved swine flu remains unknown.
The Imperial County girl fell ill on March 28 with cough and a high fever. The San Diego boy came down with similar symptoms, plus vomiting, two days later. People in both households fell ill before and after the children did, although health officials have not determined whether those were also swine flu.
Munday said his department has drawn blood from more than 20 people to be tested for antibodies to the swine flu strain, which would indicate those people had been infected even if they never had symptoms. He said some had traveled into Mexico recently but would not describe them further.
"As of yet we have not been able to come up with any explanation of why anyone would have swine flu," he said.
Molecular analysis of the virus suggests it is the product of a rare event called a gene reassortment. In a reassortment, two distinct strains of virus infect the same cell. The viruses take over the cell's genetic machinery to make new copies of themselves, mingling the genes of the two strains to create a new, essentially hybrid, strain. Six of the eight genes in the new strain are from the North American lineage of swine flu; two are from the Eurasian lineage.
The reassortment probably occurred in a pig sometime in the last decade. Both the sets of genes are slightly different from those of their original lineage, a sign that time has passed. But it's unlikely they have been in human beings very long.
"If these viruses had been circulating at low levels in humans for several years, we probably would have detected them," said Nancy Cox, head of CDC's influenza division.
The ability to find and identify rare strains of influenza virus has improved greatly in the last decade, spurred in part by the "bird flu" outbreak in Asia and the 2001 anthrax attacks.
In the last three years, 12 cases of human illness caused by swine flu strains have been investigated by the CDC. In 11 of the cases, however, those infected had direct or indirect exposure to pigs.
In 1976, a strain of swine flu caused illness in 13 soldiers at Fort Dix, in New Jersey, killing one. Fearing a pandemic, the federal government ordered emergency production of a vaccine and planned to administer it to millions of elderly and vulnerable Americans. Mass immunization was halted, however, when the virus failed to spread and some vaccine recipients got a rare neurological disorder called Guillain-Barre syndrome.

http://www.silive.com/printer/printe...ylist=national

[HenryN]

http://www.cdc.gov/mmwr/pdf/wk/mm58d0421.pdf

[HenryN]

Commentary

[HenryN]

Updated map

http://maps.google.com/maps/ms?ie=UT...3,2.905884&z=8

[HenryN]

Swine Flu Sickens 2 California Kids

CDC Believes Flu Was Contracted in Person-to-Person Spread
By Daniel J. DeNoon
WebMD Health News
Reviewed by Louise Chang, MD



April 21, 2009 -- Two California children got sick with a mysterious new strain of swine flu -- and the CDC thinks they got the pig virus via person-to-person contact.
Both kids, a 10-year-old boy from San Diego County and a 9-year-old girl from Imperial County, are now well. However, the girl had a 104.3-degree fever before she recovered. And the boy traveled by airplane from San Diego to Dallas while he still had flu symptoms.
Is this the first sign of a flu pandemic? That's possible, but not likely, says Lyn Finelli, DrPH, chief of flu surveillance at the CDC.
"While we have a low index of suspicion this is a pandemic, we are being careful to rule out any possibility," Finelli says. "We don't know yet."
"We have here detection of two cases of swine flu virus in children. We are trying to figure out where they came from and how serious they are," says Dan Jernigan, MD, MPH, deputy director of the CDC's influenza division.
The CDC has dozens of people tracing the children's contacts, beginning with close family members. Each of the children had two family members come down with the flu -- in both cases, one family member had the flu before the child had the flu, and one after.
All recovered, but flu virus was not obtained from any of these family members while they still had symptoms. Over the weekend, the CDC developed a specific test for the new swine flu virus; testing of the children's contacts is now under way. It's likely that the tests will reveal other people who recovered from the infection.
CDC has not activated its Atlanta-based command center. But California has, Finelli says, and is putting all available health care workers on the job of tracking down the children's contacts.
Both children attended school, and California authorities are planning to trace the children's school contacts.
Meanwhile, the 10-year-old boy remains in the Dallas area and has made a full recovery from his one-week symptoms of fever, cough, and vomiting.
So far, the CDC says, Texas health authorities have not found any new infections. The boy traveled to Texas with three other children unaccompanied by adults; crew members who assisted the children are now being tested.
The CDC is withholding the name of the airline that flew the boy and his three companions from San Diego to Dallas on April 3.
Swine flu viruses don't normally infect humans. When they do, it's almost always because of contact with an infected pig. But neither child had any direct contact with pigs.
Moreover, the viruses recovered from the children are not like the swine flu viruses common among pigs. That raises the specter of human-to-human spread of the virus, Finelli says.
"This virus is different, very different from that circulating in pigs. That was a red flag," Finelli told WebMD and several other news organizations. "The other red flag is both cases appeared almost simultaneously, 100 miles apart. When we see two cases [of swine flu] without animal contact that occur simultaneously and they have a different virus [than in pigs], we are concerned."

What worries the CDC is that the two cases might signal the beginning of a flu pandemic with a virus new to humans. But CDC spokesman Tom Skinner notes that it's the CDC's job to be worried. Several things about the cases are reassuring:

• Both cases were detected by routine flu surveillance.
• Southern California has unusually excellent flu surveillance -- and there has not been a large number of flu cases from unusual flu strains.
• The virus is the H1N1 strain of swine flu. There are human strains of H1N1, raising at least the possibility of cross-protection -- especially in adults.

Not reassuring is the finding that the new swine flu strain carries three genes from Eurasian swine flu bugs not known to be circulating in the U.S. The new strain apparently is a reassortant virus that assembled itself from the genes of at least two different swine flu viruses. It carries no human flu genes.
Swine flu last spurred headlines in 1976 when an outbreak of swine flu at Fort Dix, N.J., killed one healthy recruit, caused four cases of serious pneumonia, and spread to some 230 soldiers before it vanished.
It's still not clear where the 1976 virus came from or why it went away -- but it spurred widespread public alarm and a vaccination program that badly misfired before being terminated.
The CDC, the California Department of Public Health, and the health departments of Imperial and San Diego counties urge all of those counties' residents and visitors who develop flu-like symptoms to seek medical attention.
Doctors who see these patients are advised to send swab samples to state or local health authorities. They are also asked to get full interviews to ask about other family members or contacts who may be ill.

Here's the CDC's advice for all people who get flu-like symptoms, whether it's normal seasonal flu or swine flu:

• Stay home when you are sick to avoid spreading illness to co-workers and friends.
• Children with flu-like symptoms should stay home to avoid spreading illness to classmates and staff.
• Cough or sneeze into your elbow or a tissue and properly dispose of used tissues.
• Wash your hands thoroughly with soap and warm water or use an alcohol-based hand sanitizer to get rid of most germs, and avoid touching your eyes, nose, and mouth.
• Stay healthy by eating a balanced diet, drinking plenty of water, and getting adequate rest and exercise.

The new swine flu bug is resistant to the older flu drugs amantadine and rimantadine. Tests are under way to see if it remains sensitive to the newer flu drugs Tamiflu and Relenza.
The CDC announced the swine flu cases in a special MMWR Dispatch published today.

http://www.webmd.com/cold-and-flu/ne...alifornia-kids

[Shiloh]

Source: http://www.cidrap.umn.edu/cidrap/con...2109swine.html


Human swine flu cases with unique strain raise concern

Robert Roos * News Editor

Apr 21, 2009 (CIDRAP News) – Two California children who had not had contact with pigs recently recovered from infections with "unique" swine influenza viruses, raising concern about possible human-to-human transmission and putting health authorities on alert, the Centers for Disease Control and Prevention (CDC) reported today.

The two cases were in a 10-year-old boy in San Diego County and a 9-year-old girl in neighboring Imperial County, but they are apparently unrelated, the CDC said in an MMWR Dispatch report today.

"The viruses from the two cases are closely related genetically, resistant to amantadine and rimantadine [the two older flu antivirals], and contain a unique combination of gene segments that previously has not been reported among swine or human influenza viruses in the United States or elsewhere," the CDC report says.

The lack of any known exposure to pigs in the two cases increases the chance that the children contracted their infections from other people, the CDC said. The agency advised physicians to consider animal influenza virus infections in patients who recently were in the two California counties or had contact with pigs.

The CDC says it received reports of 12 human swine flu cases from December 2005 through January 2009, an increase from the previous long-term average of about one case every 1 to 2 years. The "vast majority" of such cases do not lead to human-to-human transmission, but all need to be investigated thoroughly, the agency states.

Illnesses began in March
The 10-year-old boy fell ill with fever, cough, and vomiting on Mar 30, according to the CDC. He was taken to a clinic, where he received symptomatic treatment, and he recovered in about a week. He had not received flu vaccine this season. The boy and his family said he had had no exposure to pigs.

Initial testing at the clinic indicated an influenza A virus but was negative for human subtypes H1N1, H3N2, and H5N1, the report says. A sample was sent to reference laboratories, which were unable to identify the subtype. The CDC received a sample Apr 14 and identified the virus as swine influenza A/H1N1.

The boy's mother had a nonfebrile respiratory illness in the first few days of April, and his 8-year-old brother was sick with a cough and fever on Apr 11, but no respiratory samples were taken during their illnesses.

In the other case, the CDC received an influenza specimen on Apr 17 that the Naval Health Research Center in San Diego had sent as a type A virus that couldn't be subtyped, according to the report. The CDC identified the virus as a swine influenza A/H1N1 isolate the same day.

The sample came from the 9-year-old girl, who got sick with a cough and fever (104.3ºF) on Mar 28, the report says. She was treated at an outpatient clinic with antibiotics and an antihistamine, and she recovered uneventfully. The girl reported that she had visited a fair with a pig exhibit about 4 weeks before her illness but that she had not seen the pigs, and she reported no other exposure.

The girl's 13-year-old cousin, who was living with the family, had a flu-like illness 3 days before she got sick, and her 13-year-old brother had similar symptoms on Apr 1, the CDC reports. But neither was tested for flu while they were sick.

So far, no epidemiologic link between the two cases has been found, nor have any other cases been identified involving the new strain, the report says. Case and contact investigations by the county and states health agencies are under way.

A new combination of genes
The viruses from the two patients are similar, and the majority of their genes, including the hemagglutinin gene, are similar to those of swine flu viruses that have circulated in US pigs since about 1999, the CDC reports. But the genes for the neuraminidase (NA) and matrix (M) proteins are similar to corresponding genes of Eurasian swine flu viruses.

"This particular genetic combination of swine influenza virus segments has not been recognized previously among swine or human isolates in the United States, or elsewhere based on analyses of influenza genomic sequences available on GenBank," the report states.

While there is no formal system for monitoring what viruses circulate in US swine, viruses with this combination of genes are not known to be circulating in the country, the report adds.

Testing is under way to learn whether the two viruses are susceptible to the neuraminidase inhibitor drugs oseltamivir and zanamivir.

The CDC advises that clinicians should consider animal as well as seasonal flu virus infections in patients who live in or who visited San Diego or Imperial County or were in contact with sick people from either county in the week before their illness onset. It also urges clinicians to take a nasopharyngeal swab in such cases and to contact their state or local health department to arrange for testing at a state public health lab.

CDC. Swine influenza A (H1N1) infection in two children—Southern California, March-April 2009. MMWR Dispatch 2009 Apr 21;58 [Full text]

[HenryN]

Map updated to reflect 100 miles between cases

http://maps.google.com/maps/ms?ie=UT...81,3.99353&z=8

[HenryN]

A young boy in San Diego County and a young girl in Imperial County have been infected with swine flu. Health officials say the strain of the disease has been seen before in the United States. KPBS Reporter Kenny Goldberg has more.

Health officials say the nine-year-old girl and the ten-year-old boy who came down with swine flu have fully recovered.

The mystery is how they got the disease in the first place.

Officials say the children have never met, nor have they had any contact with pigs.

Dr. Wilma Wooten is San Diego County's Public Health Officer. She says we do not have an outbreak of swine flu.

"What we do have," says Dr. Wooten, "Is a situation where there is a unique animal virus that has now been introduced into the human population, and we are conducting heightened surveillance and investigation to determine the source, and whether or not it's more common than we know."

Dr. Wooten says swine flu infections among humans are rare.

Kenny Goldberg, KPBS News.

[sharon sanders]

from a report on January 15, 2009 -


South Dakota has reported a case of swine flu in a human, a 19-year-old South Dakota State University student. The individual was ill five weeks ago and a specimen was collected December 4, 2008. The state Public Health Laboratory identified the A/H1 portion of the virus and just this week, the Centers for Disease Control and Prevention (CDC) influenza lab identified the swine components of the virus.

"Swine flu in humans is rare but it does occur," said Dr. Lon Kightlinger, State Epidemiologist for the department. "Most often, the cases occur in people with direct exposure to pigs, such as swine farm workers. Human to human transmission is very rare."

Nationally, the CDC typically receives about one report of swine flu virus in a human each year. The South Dakota case is believed to be the state's first case.

Kightlinger said the department is on enhanced surveillance for additional cases and is working closely with CDC and the U.S. Department of Agriculture on the case investigation.

The symptoms of swine flu in people are the same as those of seasonal human flu. They include a fever with a cough, sore throat, body aches, and tiredness. It is also possible to be infected and have no symptoms. There is a swine flu vaccine for pigs but because people seldom become infected with the virus, there is no human vaccine. Seasonal flu activity is low in Brookings and in the state this year.

Dr. Sam Holland, State Veterinarian, noted that swine viruses are often observed in routine poultry disease surveillance, due to the ever-present and circulating nature of influenza viruses. "We also know that the strains of flu viruses circulating in pigs do contain genes common to influenza viruses in humans. Influenza viruses are constantly circulating and mutating among birds, animals, and people so the occasional finding of a bird or swine virus in people or vice versa is not a surprise," said Dr. Holland.

http://www.medicalnewstoday.com/articles/135613.php

[HenryN]

Originally Posted by Florida1

from a report on January 15, 2009 -


South Dakota has reported a case of swine flu in a human, a 19-year-old South Dakota State University student. The individual was ill five weeks ago and a specimen was collected December 4, 2008. The state Public Health Laboratory identified the A/H1 portion of the virus and just this week, the Centers for Disease Control and Prevention (CDC) influenza lab identified the swine components of the virus.

"Swine flu in humans is rare but it does occur," said Dr. Lon Kightlinger, State Epidemiologist for the department. "Most often, the cases occur in people with direct exposure to pigs, such as swine farm workers. Human to human transmission is very rare."

Nationally, the CDC typically receives about one report of swine flu virus in a human each year. The South Dakota case is believed to be the state's first case.

Kightlinger said the department is on enhanced surveillance for additional cases and is working closely with CDC and the U.S. Department of Agriculture on the case investigation.

The symptoms of swine flu in people are the same as those of seasonal human flu. They include a fever with a cough, sore throat, body aches, and tiredness. It is also possible to be infected and have no symptoms. There is a swine flu vaccine for pigs but because people seldom become infected with the virus, there is no human vaccine. Seasonal flu activity is low in Brookings and in the state this year.

Dr. Sam Holland, State Veterinarian, noted that swine viruses are often observed in routine poultry disease surveillance, due to the ever-present and circulating nature of influenza viruses. "We also know that the strains of flu viruses circulating in pigs do contain genes common to influenza viruses in humans. Influenza viruses are constantly circulating and mutating among birds, animals, and people so the occasional finding of a bird or swine virus in people or vice versa is not a surprise," said Dr. Holland.

http://www.medicalnewstoday.com/articles/135613.php

The California cases have nothing to do with prior reports. The HA is from North America while the NA is from Eurasia. This constellation has never been reported previously.
I suspect it came from Mexico.

[sharon sanders]

from a study in 2005 -

Serologic Evidence of Human and Swine Influenza in Mayan Persons

Guadalupe Ayora-Talavera,* Juan Manuel Cadavieco-Burgos,* and Alejandro Bernardino Canul-Armas*
*Universidad Autónoma de Yucatán, Mérida, Yucatan
Suggested citation for this article

---

Antibodies against influenza viruses were detected in 115 serum samples from indigenous Mayan persons from Kochol, Yucatán. Seropositivity rates were 26.9% to A/Bayern/7/95, 40.8% to A/Sydney/5/97, 1.7% to A/Swine/Wisconsin/238/97, and 79.1% to A/Swine/Minnesota/593/99. This report is the first in Mexico of the prevalence of antibodies to swine influenza virus in humans.

Influenza virus type A has the capacity to infect humans, birds, swine, and other animals. Studies have repeatedly shown that influenza virus can move from 1 species to another. The pig has been proposed as an animal that could play a key intermediary role in interspecies transmission. Pigs are the only domesticated mammalian species that are reared in abundance and are susceptible to both avian and human influenza virus and allow productive viral replication (1,2).

In rural zones in the Mexican state of Yucatán, the "backyard system," a production system in which animals such as pigs, ducks, turkeys, and chickens are all raised in close proximity to humans, is common. This system is a traditional activity of indigenous Mayan persons, as well as other ethnic groups in Mexico, and provides an economical way to produce animals. The animals eat, live, and share space, water sources, and even food with humans; they may even be found inside houses. These activities create health concerns because of potential for the adaptation and reassortment of human and avian viruses.
Despite abundant evidence supporting interspecific transmission and genetic reassortment of influenza virus around the world, little is known about the influenza virus in humans and domesticated animals in Yucatán in southeastern Mexico. We describe serologic evidence of antibodies against influenza strains from humans and pigs in indigenous Mayan persons from Yucatán.

The Study

Kochol is located in east Yucatán, ≈20 km from the municipality of Maxcanu. The 1,207 residents are mostly dedicated to agricultural activities (3). The population has high illiteracy rates, poor environmental health, and crowded and inadequate housing. In Kochol, pigs are found around the town, walking in and out of houses. All pigs are wild or criollos. Some families have 1–18 pigs. For this study, serum samples from 115 persons were made available by the health official of Kochol in 2000. Serum samples were from Kochol residents who came to the health service for any medical condition and required laboratory tests.

Samples were treated with receptor-destroying enzyme from Vibrio cholera and heated at 56°C in a water bath to inactivate nonspecific inhibitors (4). The following 4 influenza strains were used to detect antibodies: A/Swine/Wisconsin/238/97 (classical swine H1N1), A/Bayern/7/95 (human H1N1), A/Sydney/5/97 (human H3N2), and A/Swine/Minnesota/593/99 (reassortant swine H3N2); all were grown in 10-day-old embryonated chicken eggs. The hemagglutination inhibition tests were performed by using chicken erythrocytes at a concentration of 0.5%. A sample was considered seropositive to H1 and H3 when the HA titer was >1:40. Each serum sample was tested against chicken receptor–destroying enzymes in the absence of virus to rule out induction of nonspecific hemagglutination.

Conclusions

As shown in Table 1, reactivity rates were uniformly high to H3 subtype influenza virus. These results agree with previous serologic tests of human serum samples from Yucatán (G. Ayora-Talavera, unpub. data). H1 viruses likely circulate at a lower frequency than H3 viruses. Overall, 31 (26.9%) of 115 samples were positive to H1, whereas 93 (80.8%) of 115 were seropositive to H3. The results indicate that influenza virus infection occurs in a large proportion of persons in this area. In general, Mexican persons are not vaccinated, so we can be sure that the antibodies detected reflect actual infection (5). Samples were divided into 5 age groups (Table 2). By analyzing the percentage of seropositive persons in different age groups, we observed that persons 15–24 years of age were most commonly seropositive. Through virus surveillance in Yucatán, we have also observed a very low circulation of influenza A H1. From ≈1,500 throat swabs collected in 5 years, no sample has been found to contain H1 influenza by immunofluorescence assay, and only 5 viruses have been detected with reverse transcription–polymerase chain reaction (G. Ayora-Talavera, unpub. data).

The highest seropositivity rates across all age groups were detected with the A/Sw/Minnesota virus as antigen. Although this strain was isolated from American pigs, the HA, NA, and PB1 genes are of human origin (6). Taking into consideration the cutoff values of this study, seropositivity to the swine H1 virus was only detected in 2 samples, from persons 43 and 59 years of age. However, lower titers were detected in 4 more persons 33–55 years of age. The weak reactivity to this virus could suggest a past exposure of adult persons to viruses of swine origin, a situation that has not occurred in persons >30 years of age.

The animal population owned by persons in this study consisted of pigs (68.7%), chickens (73%), and ducks (17.3%). Any combination of 2 or 3 species was kept by 54.7%. The range of the number of animals owned was 0–12 (mean 2.9) pigs, 0–60 (mean 7) chickens, and 0–23 (mean 0.93) ducks. Since we did not have avian antigens available, serum samples collected from humans, pigs, chickens, and ducks were not tested for exposure to avian influenza viruses.
The relative risk of being seropositive for H1 or H3 viruses from exposure to pigs was 1.93 with human H1 (95% confidence interval [CI] 1.2–3.0), 0.88 with human H3 (95% CI 0.55–1.4), 0.6 with swine H1 (95% CI 0.08–4.2), and 1.0 with swine H3 (95% CI 0.62–1.6).

Serologic evidence of swine antibodies in persons in contact with pigs has been reported in several studies (7–12). In Mexico, apart from this report, no information about the prevalence of antibodies to swine influenza virus in humans exists. The only information available comes from a study carried out on pig farms in central Mexico, where the subtype H1 is prevalent in 20% of pigs (13) and from a previous study from Yucatán, where the most prevalent subtype in pig farms is H3 (65%) and H1 (20%) (14).

As a result of the Mexican outbreak of HPAI H5N2, the Mexican Ministry of Agriculture (SAGARPA) implemented a national surveillance system in all chicken farms (NOM-044-ZOO-1995). Yucatán is considered a free state for avian influenza virus. Chicken farms are sampled 3 times a year for serologic surveillance, and 10% of the backyard flocks are sampled annually (15). On the other hand, swine influenza is not considered within the SAGARPA priorities, and no surveillance program exists for swine farms, although we found serologic evidence that in Yucatán influenza H3 subtype is highly prevalent (14).
Asia has been considered as an epicenter for the generation of pandemic influenza virus, and some factors are high densities of humans and animals in close contact (1). In Yucatán, the backyard system is a common practice, and human and animal encounters could lead to generation of novel reassortant viruses here as well.

Acknowledgements

We thank Chris Olsen for technical assistance and reviewing the manuscript and L. ´t Mannetje for his helpful advice on the manuscript.
This research was supported by CONACYT-SISIERRA CIR-BIO980203 and Universidad Autónoma de Yucatán.
Dr. Ayora-Talavera is an associate researcher and lecturer at the University of Yucatan. Her research interest is the molecular epidemiology of respiratory viruses, with emphasis on influenza virus.

References

1. Webster RG, Bean WJ, Gorman OT, Chambers TM, Kawaoka Y. Evolution and ecology of influenza A viruses. Microbiol Rev. 1992;56:152–79.
2. Olsen CW. Influenza in pigs and their role as the intermediate host. In: Nicholson KG, Cox N, Hay AJ, Webster RG, editors. Textbook of influenza. 2nd ed. London: Blackwell Science. In press 2004.
3. Tabulados Básicos. Estados Unidos Mexicanos. XII Censo General de Población y Vivienda 2000. Tomo I. 552 pp. Instituto Nacional de Estadística, Geografía e Informática (INEGI). México, D.F. 2000.
4. Kendal AP, Pereira MS, Shekel J. Concepts and procedures for laboratory-based influenza surveillance. Geneva: World Health Organization; 1982.
5. Van Essen GA, Palache AM, Forleo E, Fedson DS. Influenza vaccination in 2000: recommendations and vaccine use in 50 developed and rapidly developing countries. Vaccine. 2003;21:1780–5.
6. Zhou NN, Senne DA, Landgraf JS, Swenson SL, Erickson G, Rossow K, et al. Emergence of H3N2 reassortant influenza A viruses in North American pigs. Vet Microbiol. 2000;74:47–58.
7. Kluska V, Macku M, Mensik J. Evidence of swine influenza antibodies in human. Cesk Pediat. 1961;116:408–14.
8. Woods GT, Hanson LE, Hatch RD. Investigation of four outbreaks of acute respiratory disease in swine and isolation of swine influenza virus. Health Lab Sci. 1968;5:218–24.
9. Schnurrenberger PR, Woods GT, Martin RJ. Serologic evidence of human infection with swine influenza virus. Am Rev Respir Dis. 1970;102:356–61.
10. Shu LL, Zhou NN, Sharp GB, He SQ, Zhang TJ, Zou WW, et al. An epidemiological study of influenza viruses among Chinese farm families with household ducks and pigs. Epidemiol Infect. 1996;117:179–88.
11. Zhou N, He S, Zhand T, Zou W, Shu L, Sharp GB, et al. Influenza infection in humans and pigs in southeastern China. Arch Virol. 1996;141:649–61.
12. Olsen CW, Brammer L, Easterday BC, Arden N, Belay E, Baker I, et al. Serologic evidence of H1 swine influenza virus infection in swine farm residents and employees. Emerg Infect Dis. 2002;8:814–9.
13. Rodríguez TJ, Ramírez MH, Carreón NR, Mercado GC. Muestreo serológico a nivel de rastro para detectar anticuerpos contra el virus de influenza porcina. Veterinaria de México. 1996;27:17–21.
14. Álvarez FM, Rodríguez BJC, Ciprián CA, Rodríguez GL, Ayora TG, Segura CJC. Perfil serológico del virus de influenza porcinA, Micoplasma hyopneumoniae y Actinobacillus pleuropneumoniae en granjas del estado de Yucatan. Veterinaria de México. 2004;35:295–305.
15. Dirección de Campañas Zoosanitarias y CPA. Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria. Situación Zoosanitaria en los Estados de la República Mexicana (al 9 de Febrero de 2004). SENASICA 2003. México, D.F.

Table 1. Hemagglutination inhibition antibodies to influenza virus, Kochol, Yucatán
No. samples	Titer	Month	No. (%) positive samples
			A/Bayern/7/97 (H1N1)	A/Sw/Wis/238/97 (H1N1)	A/Sw/Mn/593/99 (H3N2)	A/Sydney/5/97 (H3N2)
73		June	22 (30)	2 (2.7)	59 (80.8)	32 (43.8)
	0		41	67	4	10
	10		6	2	2	12
	20		4	2	8	19
	40		5	2	9	9
	80		6		11	17
	160		7		18	4
	320					2
	640		4		18
	1,280				3
35		July	8 (23)	0	26 (74)	14 (40)
	0		18		5	13
	10		6		2	2
	20		3		2	6
	40		3		7	8
	80		3		10	4
	160		1		4	2
	640		1		4
	1,280				1
7		August	1 (14)	0	6 (85.7)	1 (14)
	0		4		1	3
	10		1			1
	20		1			3
	40		1		1	1
	160				4
	320				1

Table 2. Specific hemagglutination inhibition antibodies by age group, Kochol, Yucatán
Age group	N	n (%)
		A/Bayern/7/97 (H1N1)	A/Sw/Wis/238/97 (H1N1)	A/Sw/Mn/593/99 (H3N2)	A/Sydney/5/97 (H3N2)
8–14	16	4 (25)	0	14 (87)	9 (56)
15–24	33	13 (39)	0	29 (88)	14 (42)
25–34	28	5 (16)	0	22 (78)	9 (32)
35–44	24	4 (16)	1 (4)	16 (66)	9 (37)
45–53	14	4 (33)	1 (8)	10 (71)	6 (43)

Suggested citation for this article:
Ayora-Talavera G, Cadavieco-Burgos JM, Canul-Armas AB. Serologic evidence of human and swine influenza in Mayan persons. Emerg Infect Dis [serial on the Internet]. 2005 Jan [date cited]. Available from http://www.cdc.gov/ncidod/EID/vol11no01/04-0554.htm


http://www.cdc.gov/ncidod/EID/vol11no01/04-0554.htm

[HenryN]

Commentary

[gsgs]

how do European and American swine come into contact ?
husbandry,meat,imports of new races for mixing ,
imports of Ferkel for mästen ?

[camster]

Originally Posted by niman

Map updated to reflect 100 miles between cases

http://maps.google.com/maps/ms?ie=UT...81,3.99353&z=8

This map is a little misleading as it put the San Diego case in Oceanside. It was collected from a clinic in San Ysidro, which is about 20 miles south of San Diego proper, close to the border. I'm sure this is something google did automatically and not intentional error, just thought I would point it out.

--camster

[AlaskaDenise]

Originally Posted by niman

Commentary

Commentary

Swine H1N1 In Southern California Children Raise Concerns

Recombinomics Commentary 01:27
April 22, 2009

Patient A. On April 13, 2009, CDC was notified of a case of respiratory illness in a boy aged 10 years who lives in San Diego County, California. The patient had onset of fever, cough, and vomiting on March 30, 2009.

The patient's mother had respiratory symptoms without fever in the first few days of April 2009, and a brother aged 8 years had a respiratory illness 2 weeks before illness onset in the patient and had a second illness with cough, fever, and rhinorrhea on April 11, 2009.

patient B, is a girl aged 9 years who resides in Imperial County, California, adjacent to San Diego County. On March 28, 2009, she had onset of cough and fever (104.3°F [40.2°C]).

The patient's brother aged 13 years had influenza-like symptoms on April 1, 2009, and a male cousin aged 13 years living in the home had influenza-like symptoms on March 25, 2009, 3 days before onset of the patient's symptoms.

The above comments from today’s MMWR dispatch describe two children in southern California infected with H1N1 swine flu. The isolates are similar and have an unusual constellation of genes. Although all 8 are reported as being swine, the NA and MP sequences are European, while the other 6 gene segments are North American. The HA, NA, and MP sequences of A/California/04/2009 have been placed on deposit at GISAID.

The lack of contact between the two children, as well as a lack of contact with swine, suggests the virus is spreading human to human. Although both children recovered, the presence of swine H1N1 in humans raises concerns of recombination with H1N1 seasonal flu, including the acquisition of H274Y.

Moreover, the 1918 pandemic strain was a recombinant between human H1N1 and swine H1N1.

The likely ability of this swine H1N1 to transmit efficiently in humans is cause for concern.

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[AlaskaDenise]

Originally Posted by niman

Commentary

Commentary

Human Transmission of Swine H1N1 in Southern California

Recombinomics Commentary 04:10
April 22, 2009

"This virus is different, very different from that circulating in pigs. That was a red flag," Finelli told WebMD and several other news organizations. "The other red flag is both cases appeared almost simultaneously, 100 miles apart.

The above comments leave little doubt that the H1N1 swine flu is being efficiently transmitted human to human in southern California. The unique constellation of swine genes has not been reported previously and the two cases do not have swine contacts. Moreover, family members had symptoms before and after the confirmed cases, indicating the H1N1 spread efficiently within each family.

However, none of the family members were tested because the H1N1 was mild and they recovered without treatment. The two cases were identified through routine surveillance, but such identifications require sero-typing. The swine sequences will test positive for influenza A.

Therefore the virus can silently spread, which resulted in two independent detections 100 miles apart - see map for general locations. Specific locations within San Diego and Imperial countries have not been released, but upcoming testing of classmates should lead to the identification of location(s).

Although both cases recovered without hospitalization, the spread of the swine H1N1 in a human population is cause for concern. The virus can adapt and spread more efficiently. Moreover, co-infection of H1N1 swine flu and osletamivir resistant H1N1 season flu can lead to acquisition of H274Y by the swine flu via recombination or reassortment. Swine H1N1 with human H1 and N1 have been reported. Moreover, the swine flu can also infect swine and acquire more polymorphisms that could lead to increased virulence.

The 1918 pandemic strain has polymorphism from swine and human H1N1 in all eight gene segments. Similar swapping of polymorphism in human co-infected with season and swine H1N1 can lead to rapid evolution. Therefore, release of both sets of sequences, as well as new sequences, which will likely be detected in the near term in the United States and Mexico, would be useful.

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