2004 WHO Situation Updates - Avian Influenza Archive

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Avian influenza A(H5N1) - update 29: Situation (human) in Viet Nam


23 February 2004

Situation (human) in Viet Nam

Laboratory tests have confirmed an additional case of H5N1 infection in Viet Nam. The case is a 16-month-old baby girl from Dong Nai Province. She has been hospitalized since 16 February in Ho Chi Minh City and remains in stable condition.


To date, Viet Nam has reported 23 confirmed cases, of which 15 have been fatal.



http://www.who.int/csr/don/2004_02_23/en/print.html



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Confirmed Human Cases of Avian Influenza A(H5N1)


23 February 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">9</td> <td align="center" width="32%">7</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">23</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">32</td> <td align="center" width="32%">22</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.

http://www.who.int/csr/disease/avian_influenza/country/cases_table_2004_02_23/en/print.html

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Avian influenza A(H5N1) - update 30: Situation (human) in Thailand


27 February 2004

The Ministry of Public Health in Thailand has confirmed the country’s tenth case of H5N1 infection. The case is a 47-year-old woman from Lopburi Province who has fully recovered. She fell ill with fever and cough on 3 February and was diagnosed with pneumonia on 20 February. Hospital discharge followed 5 days later. She had exposure to diseased and dead chickens at her home in January.

To date, Thailand has reported 10 cases, of which 7 have been fatal.



http://www.who.int/csr/don/2004_02_27/en/print.html




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Confirmed Human Cases of Avian Influenza A(H5N1)


27 February 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">10</td> <td align="center" width="32%">7</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">23</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">33</td> <td align="center" width="32%">22</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.
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Avian influenza A(H5N1)- update 31: Situation (poultry) in Asia: need for a long-term response, comparison with previous outbreaks


2 March 2004


During last week’s emergency meeting in Bangkok, Thailand, officials from FAO, OIE, and WHO drew attention to several unique features of the current outbreaks of H5N1 in poultry in Asia, in particular its geographical distribution, rate of spread and severity of which are unprecedented.

Prospects for rapid control are inconsistent with worldwide experience, over more than four decades, with previous outbreaks, which have all been much smaller in scope and inherently less challenging. Even in countries with good surveillance, adequate resources, and geographically limited outbreaks, control has often taken up to two years. For these reasons and others, WHO has cautioned against assumptions that the outbreaks can be controlled in the immediate future.


WHO has described the serious public health implications of these outbreaks in a previous update.


Up to the end of 2003, highly pathogenic avian influenza (HPAI) was considered a rare disease. Since 1959, only 21 Outbreakshad been reported worldwide. The majority occurred in Europe and the Americas. Of the total, only five resulted in significant spread to numerous farms, and only one was associated with spread to other countries.


Since mid-December 2003, eight Asian countries have confirmed outbreaks of highly pathogenic avian influenza caused by the H5N1 strain. Most of these countries are experiencing outbreaks of this disease for the first time in their histories. In several, outbreaks have been detected in virtually every part of the country.


Over the past two months, more than 100 million birds have either died of the disease or been culled in Asia. This figure is greater than the total number of poultry affected, over years, in the world’s previous five largest outbreaks combined.


Worldwide experience since 1959 supports official statements about the unprecedented nature of the present situation and the challenges for control. Unique features in the present situation include:


- Concentration of poultry in backyard farms.In several countries experiencing outbreaks, up to 80% of poultry are produced on small farms and backyard holdings in rural areas, where poultry range freely. In China, 60% of the country’s esitmated 13.2 billion chickens are raised on small farms in close proximity to humans and domestic animals, including pigs. This situation makes implementation of strict control measures, essential to the control of previous outbreaks, extremely difficult. These control measures – including bird-proof, ecologically controlled housing, treatment of water supplies, disinfection of all incoming persons, equipment, and vehicles, prevention of contact with insects, rodents, and other mechanical vectors – cannot be applied on small rural farms and backyard holdings.


– Economic significance of poultry production. Poultry production contributes greatly to the economies and food supplies of affected countries. The agricultural sector faces the challenge of minimizing losses to industry and subsistence farmers in ways that also reduce health risks for humans. Because many people in the region are so dependent on poultry, appropriate culling may be difficult to implement.


– Lack of control experience. Since the disease is new to most countries in the region, very little experience exists at national and international levels to guide the best country-specific control measures. In some countries, announcements of successful culling in certain areas are being followed by subsequent eruptions of disease in the same areas, suggesting reintroduction of the virus, continuing presence in the environment, or inadequate verification of outbreak control.


– Lack of resources. Several countries with very widespread outbreaks lack adequate infrastructure and resources, including resources to compensate farmers and thus encourage compliance with government recommendations. In some countries that have announced outbreaks, neither surveillance to detect the extent of spread nor culling of animals known to be infected is taking place.


– The scale of international spread. With so many adjacent countries affected, a region-wide strategy will be needed to ensure that gains in one country are not compromised by inadequate control in another.
These unique features will make rapid control and long-term prevention of recurrence extremely difficult to achieve.


Culling remains the first line of action, as recommended by FAO, OIE, and WHO, for bringing the current outbreaks under control. Unlike other economically important domestic animals, poultry raising takes place in a very short production system. Provided sufficient resources are available to replace culled poultry stock, countries should not postpone aggressive culling because of fears of long-term consequences on poultry production.


Wild birds can play a role in introducing a virus of low pathogenicity into domestic flocks where, if allowed to circulate for several months, it can mutate into a highly pathogenic form. No evidence to date indicates that wild birds are the source of the present outbreaks of highly pathogenic H5N1 avian influenza. Wild birds should not be culled.


Previous outbreaks of highly pathogenic avian influenza worldwide


<table border="1" height="527" width="67%"> <tbody><tr> <td height="19" width="21%">Year</td> <td height="19" width="36%">Country/area</td> <td height="19" width="27%">Domestic birds affected</td> <td height="19" width="16%">Strain</td> </tr> <tr> <td height="19" width="21%">1959 </td> <td height="19" width="36%">Scotland</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H5N1</td> </tr> <tr> <td height="19" width="21%">1963 </td> <td height="19" width="36%">England</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H7N3</td> </tr> <tr> <td height="19" width="21%">1966 </td> <td height="19" width="36%">Ontario (Canada)</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H5N9</td> </tr> <tr> <td height="19" width="21%">1976 </td> <td height="19" width="36%">Victoria (Australia)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N7</td> </tr> <tr> <td height="21" width="21%">1979 </td> <td height="21" width="36%">Germany</td> <td height="21" width="27%">chicken</td> <td height="21" width="16%">H7N7</td> </tr> <tr> <td height="19" width="21%">1979 </td> <td height="19" width="36%">England</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H7N7</td> </tr> <tr> <td height="19" width="21%">1983–1985 </td> <td height="19" width="36%">Pennsylvania (USA)*</td> <td height="19" width="27%">chicken, turkey</td> <td height="19" width="16%">H5N2</td> </tr> <tr> <td height="19" width="21%">1983 </td> <td height="19" width="36%">Ireland</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H5N8</td> </tr> <tr> <td height="19" width="21%">1985 </td> <td height="19" width="36%">Victoria (Australia)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N7</td> </tr> <tr> <td height="19" width="21%">1991 </td> <td height="19" width="36%">England</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H5N1</td> </tr> <tr> <td height="19" width="21%">1992 </td> <td height="19" width="36%">Victoria (Australia)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N3</td> </tr> <tr> <td height="19" width="21%">1994 </td> <td height="19" width="36%">Queensland (Australia)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N3</td> </tr> <tr> <td height="19" width="21%">1994–1995 </td> <td height="19" width="36%">Mexico*</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H5N2</td> </tr> <tr> <td height="19" width="21%">1994 </td> <td height="19" width="36%">Pakistan*</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N3</td> </tr> <tr> <td height="19" width="21%">1997 </td> <td height="19" width="36%">New South Wales (Australia)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N4</td> </tr> <tr> <td height="19" width="21%">1997 </td> <td height="19" width="36%">Hong Kong (China)*</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H5N1</td> </tr> <tr> <td height="19" width="21%">1997 </td> <td height="19" width="36%">Italy</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H5N2</td> </tr> <tr> <td height="19" width="21%">1999–2000 </td> <td height="19" width="36%">Italy*</td> <td height="19" width="27%">turkey</td> <td height="19" width="16%">H7N1</td> </tr> <tr> <td height="19" width="21%">2002</td> <td height="19" width="36%">Hong Kong (China)</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H5N1</td> </tr> <tr> <td height="19" width="21%">2002 </td> <td height="19" width="36%">Chile</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N3</td> </tr> <tr> <td height="19" width="21%">2003 </td> <td height="19" width="36%">Netherlands*</td> <td height="19" width="27%">chicken</td> <td height="19" width="16%">H7N7</td> </tr> </tbody></table> *Outbreaks with significant spread to numerous farms, resulting in great economic losses. Most other outbreaks involved little or no spread from the initially infected farms.


Observations from previous outbreaks (1959–2003)
Outbreaks of highly pathogenic avian influenza can be extremely difficult to control, even under favourable conditions (concentration of infected birds in well-maintained commercial production facilities, limited geographical occurrence).


– The 1983 Pennsylvania (USA) outbreak took two years to control. Some 17 million birds were destroyed at a direct cost of US$62 million. Indirect costs have been estimated at more than US$250 million.



– The 2003 outbreak in the Netherlands spread to Belgium and Germany. In the Netherlands, more than 30 million birds - a quarter of the country’s poultry stock – were destroyed. Some 2.7 million were destroyed in Belgium, and around 400,000 in Germany. In the Netherlands, 89 humans were infected, of whom one (a veterinarian) died. In that outbreak, measures needed to protect the health of poultry workers, farmers, and persons visiting farms included wearing of protective clothing, masks to cover the mouth and nose, eye protection, vaccination against normal seasonal human influenza, and administration of prophylactic antiviral drugs.


Control is even more difficult in countries with dense poultry populations.



– The Italian outbreak of 1999–2000 caused infection in 413 flocks, including 25 backyard flocks, and resulted in the destruction of around 14 million birds. Control was complicated by the occurrence of cases in areas with extremely dense poultry populations. Compensation to farmers amounted to US$63 million. Costs for the poultry and associated industry have been estimated at US$620 million. Four months after the last outbreak ended, the virus returned in a low-pathogenic form, rapidly causing a further 52 outbreaks.


– Although the last outbreak of highly pathogenic avian influenza in Mexico occurred in 1995, the causative agent – the H5N2 strain – has never been entirely eliminated from the country, in its present low-pathogenicity form, despite years of intense efforts, including the administration of more than 2 billion doses of vaccines of varying efficacy. Similarly, the vaccination policy pursued in Pakistan does not appear to have resulted in eradication of the causative agent.


Avoidance of contact between poultry and wild birds, especially ducks and other waterfowl, can help prevent the introduction of a low-pathogenicity virus into domestic flocks. Although no evidence to date has conclusively linked the current outbreaks with wild migratory birds in Asia:



– Several of these outbreaks have been linked to contact between free-ranging flocks and wild birds, including the shared use of water sources. Faecal contamination of water supplies is considered a very efficient way for waterfowl to transmit the virus. Virus (low-pathogenicity) has been readily recovered from lakes and ponds where migratory birds congregate.


– An especially risky practice is the raising of small numbers of domestic ducks on a pond in proximity to domestic chicken and turkey flocks. Domestic ducks attract wild ducks, and provide a significant link in the chain of transmission from wild birds to domestic flocks.


Aggressive control measures, including culling of infected and exposed poultry, are recommended for avian influenza virus subtypes H5 and H7 even when the virus initially shows low pathogenicity. (H5 and H7 are the only subtypes implicated in outbreaks of highly pathogenic disease.)


– Several of the largest outbreaks (Pennsylvania, Mexico, Italy) initially began with mild illness in poultry. When the virus was allowed to continue circulating in poultry, it eventually mutated (within 6 to 9 months) into a highly pathogenic form with a mortality ratio approaching 100%. Moreover, the initial presence of low-pathogenicity virus in these outbreaks complicated diagnosis of the highly pathogenic form.



http://www.who.int/csr/don/2004_03_02/en/print.html




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Confirmed Human Cases of Avian Influenza A(H5N1)


2 March 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">10</td> <td align="center" width="32%">7</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">23</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">33</td> <td align="center" width="32%">22</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.
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Confirmed Human Cases of Avian Influenza A(H5N1)


5 March 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">10</td> <td align="center" width="32%">7</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">22*</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">32</td> <td align="center" width="32%">22</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.


* After a review of laboratory information held on cases of influenza A/H5 by the Ministry of Health of Vietnam and the WHO Country Office Vietnam, one case has been reclassified from confirmed to probable. This individual had a high titre for H5 antibodies on sera collected 15 days after onset using the microneutralization test.

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Avian influenza A(H5N1)- update 32: Situation (human) in Thailand


9 March 2004

The Ministry of Public Health in Thailand has today confirmed an additional case of H5N1. The case is a 29-year-old man from Nakhon Ratchasima Province. He developed symptoms on 13 February, was admitted to hospital on 20 February, and was discharged on 7 March. He gave a history of exposure to diseased and dead chickens.


To date, Thailand has reported 11 laboratory confirmed cases of H5N1 infection in humans, of which 7 have been fatal.



http://www.who.int/csr/don/2004_03_09/en/print.html




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Confirmed Human Cases of Avian Influenza A(H5N1)


9 March 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">11</td> <td align="center" width="32%">7</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">22</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">33</td> <td align="center" width="32%">22</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.
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Avian influenza A(H5N1)- update 33: Situation (human) in Thailand


17 March 2004

The Ministry of Public Health in Thailand has confirmed another case of human infection with H5N1 avian influenza. The case, which was fatal, was a 39-year-old woman from Ayudhaya Province. She developed symptoms on 1 March, was hospitalized on 3 March, and died on 12 March.


To date, Thailand has reported 12 confirmed cases, 8 of them fatal.



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Confirmed Human Cases of Avian Influenza A(H5N1)


17 March 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">12</td> <td align="center" width="32%">8</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">22</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">34</td> <td align="center" width="32%">23</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.
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Avian influenza A(H5N1)- update 34: Situation (human) in Viet Nam


22 March 2004
Situation (human) in Viet Nam: media reports of a new human case


WHO is aware of media reports of a new fatal case of H5N1 infection in a 12-year-old boy from a southern province in Viet Nam. According to the media, the boy was hospitalized on 13 March and died two days later.
WHO has asked health authorities in Viet Nam for details about the case but has not yet received confirmatory information.


If confirmed, this will be the first reported case in Viet Nam since 20 February, when authorities announced infection in a 16-month old girl hospitalized on 16 February.



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Confirmed Human Cases of Avian Influenza A(H5N1)


24 March 2004

<table border="1" cellspacing="0" width="79%"> <tbody><tr> <td width="31%">

Country/Territory

</td> <td width="37%">

Total cases

</td> <td width="32%">

Deaths

</td> </tr> <tr> <td width="31%">Thailand</td> <td align="center" width="37%">12</td> <td align="center" width="32%">8</td> </tr> <tr> <td width="31%">Viet Nam</td> <td align="center" width="37%">22</td> <td align="center" width="32%">15</td> </tr> <tr> <td width="31%">Total</td> <td align="center" width="37%">34</td> <td align="center" width="32%">23</td> </tr> </tbody></table> Notes

Total number of cases includes number of deaths.
WHO reports only laboratory-confirmed cases.
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Avian influenza A(H7) human infections in Canada


5 April 2004

The first human case of avian influenza A(H7) in British Columbia occurred in a person who was involved in culling of infected birds on 13-14 March. On 13 March, he may have been accidentally exposed in the eye. On 16 March, the individual reported conjunctivitis and nasal discharge.



Treatment with oseltamavir, an antiviral drug active against influenza A viruses, began on 18 March. On 30 March, Health Canada concluded that this case was caused by avian influenza A(H7). Health Canada informed WHO of this case on 31 March. The patient's symptoms have fully resolved.


On 2 April, WHO was informed by Health Canada of a second poultry worker in British Columbia identified with avian influenza A(H7). This worker developed conjunctivitis in March 25 after close contact with infected birds. He was treated with oseltamivir on 25 March and his symptoms resolved.


Based on this epidemiological information provided by Health Canada, the World Health Organization today raised the global pandemic preparedness level from 0.1 to 0.2 for the Canadian outbreak.


Global pandemic preparedness levels are dictated by the epidemiological situation for each local event. Level 0.2 means that more than one human case caused by a new subtype of influenza virus has been identified in the local event.


In Asia, another avian influenza virus, A(H5N1), has been responsible for 34 reported human illnesses and 23 deaths. The existing global preparedness level of 0.2 for the avian influenza in Asia remains unchanged.


Preparedness levels have been organized into a matrix established by WHO in 1999(WHO Influenza Pandemic Preparedness plan). When a preparedness level is raised to 0.2, affected countries are advised to step up their surveillance in persons exposed to affected poultry, to organize special investigations to better understand the new virus, to advise persons at risk to wear protected clothing, and to consider the use of antivirals and normal human influenza vaccine.


WHO has been informed that Canada has taken all required actions in response to the current avian influenza A(H7) outbreak in British Columbia.

The new pandemic preparedness level for avian influenza A(H7) also means that WHO will begin a series of activities to obtain the virus, characterize it, and assess the needs for diagnostics and vaccine development.



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Assessment of risk to human health associated with outbreaks of highly pathogenic H5N1 avian influenza in poultry


14 May 2004


Background

In late January 2004, WHO activated its influenza pandemic preparedness plan in response to confirmation, in Viet Nam and Thailand, of human cases of severe disease caused by an H5N1 strain of avian influenza. These and subsequent human cases, reported through mid-March, were directly linked to outbreaks of highly pathogenic H5N1 avian influenza in the poultry populations of these two countries.


From mid-December 2003 through February 2004, outbreaks of H5N1 infection in poultry were detected in six additional Asian countries (Cambodia, China, Indonesia, Japan, Laos, and the Republic of Korea). The outbreaks have been historically unprecedented in their geographical scope, international spread, and economic consequences for the agricultural sector. More than half of the affected countries experienced highly pathogenic avian influenza for the first time in their histories. The challenges for control have been considerable.


The implications of these events for human health are two-fold. First, the H5N1 strain has demonstrated its capacity to infect humans and cause severe disease, with high fatality, on three separate occasions beginning in 1997. The 2004 outbreak in humans, which is the largest recorded, resulted in 34 officially reported cases, of which 23 were fatal. The disease in humans has no vaccine to confer protection and no specific treatment once illness becomes severe.


A second and greater concern is the possibility that a new virus subtype with pandemic potential could emerge. Pandemics recur periodically yet unpredictably, and are invariably associated with high morbidity and mortality and great social and economic disruption.


Risk assessment

In the present situation, the risks to human health remain so long as H5N1 continues to circulate in domestic poultry. In several affected countries, surveillance and reporting systems for both human and animal disease are weak. The absence of reported human cases cannot be taken as assurance that the threat to human health no longer exists.


Assessment of the risk to humans needs to be based on a risk assessment of the disease situation in poultry that considers the prevalence of highly pathogenic avian influenza and the adequacy of the surveillance system. A reliable system of review and verification is needed to ascertain that poultry are disease-free in an area or country. Equally important is a robust surveillance system for human respiratory illnesses that might signal transmission of avian H5N1 infection to humans.


Control in poultry populations

Control efforts, which have necessitated the culling of more than 100 million birds, have reduced the risk to humans. However, it cannot be assumed, because of difficulties in the collection of surveillance data, that the virus has been eliminated in poultry populations and that the risk to human health no longer exists.


In April, some countries on the verge of declaring their outbreaks over have either detected a recurrence of infection in areas thought to have been freed of the disease or reported a continuing spread of the disease to new areas. Rumours of new outbreaks in May are awaiting confirmation. WHO has repeatedly warned about the dangers of premature declarations of disease-free status.


The need to apply strong surveillance, control and biosecurity measures has been stressed in order to ensure that new outbreaks are detected and contained immediately, and to prevent re-introduction into disease-free areas. Without such measures, further outbreaks, and further spread within and between countries are likely to occur.


Proposed immediate actions

Because of uncertainties about the disease situation in poultry and the potentially severe consequences for human health, WHO is calling to:

• continue to work towards elimination of H5N1 in all poultry populations, including small holdings as well as commercial flocks;
• promptly report to relevant authorities and organizations new outbreaks in poultry;
• put in place mechanisms to verify control progress and eventually monitor freedom from the disease;
• ensure close collaboration between public health and agricultural sectors and veterinary services;
• strengthen communicable disease surveillance in humans and collect and provide the data needed for an accurate assessment of risks to human health;
• share viruses with laboratories in the WHO Global Influenza Surveillance Network.

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Avian influenza - Current evaluation of risks to humans from H5N1 following recent reports


8 July 2004

Avian influenza home page


In the last two weeks, avian influenza appears to have re-emerged in poultry in several countries in Asia. These outbreaks could either be new outbreaks of Highly Pathogenic Avian Influenza A(H5N1) virus or a continuation of the outbreaks first reported earlier in the year. These events, in addition to two new research reports -- about the virus becoming increasingly pathogenic and becoming more widespread in birds in the region -- fuel the World Health Organization's concern about the threat the virus poses to human health.


WHO has been concerned about this virus, influenza A(H5N1), because of its threat to humans both in farm settings in Asia and its greater, potentially global risk. Several countries in Asia have witnessed this virus crossing the species barrier, moving from infected chickens or ducks directly into humans in three documented outbreaks since 1997. These direct human infections have produced severe and sometimes fatal outcomes. Moreover, the virus has the potential to acquire the ability to spread easily from human to human, and thus, trigger a global influenza pandemic.


Now, two research reports have added to our understanding of this virus. First, members of China's Ministry of Agriculture and colleagues reported in a paper published last week in the Proceedings of the National Academy of Sciences that the virus appears to be widespread in domestic ducks in southern China. Further, the scientists found that the virus is causing increasingly severe disease. However, these trials were done in mice and may not have a direct implication for humans.


This week, the journal Nature published a report which indicates domestic and wild birds in the region may have contributed to the increasing spread of the virus and suggests that the virus is gaining a stronger foothold in the region. These observations suggest that control of the virus may be even more difficult than thought in the spring.


Effective risk management tools exist to control outbreaks of influenza A(H5N1) when they are detected in poultry operations. China, for example, was quick to employ these tools last week when an outbreak was discovered in Anhui province. These risk management measures include the culling of infected and exposed birds, stringent biosecurity measures and vaccination. While this approach can still take months or even years to contain the virus completely, these methods have been effective in the past.


However, tools to assess the risk to human health are less well developed. While recent reports indicate the virus has been present consistently in the environment for the last several years, it has still not acquired the ability to infect humans easily. Why? Is there something about this virus which resists this development? Given the recent reports, WHO urges and offers assistance that such risk assessment activities, including surveillance in animals and humans, and strain analysis, be undertaken as soon as possible.


More knowledge of the virus could be acquired if WHO had full access to all virus isolates and clinical specimens from recent outbreaks. All H5N1 viruses are not the same, and how they differ could provide important insights. For example, the work reported in Nature suggests that the Indonesian avian influenza virus, while belonging to the genotype of viruses seen in Viet Nam and Thailand, is also distinct. What, if any, impact does this difference have? With this information, public health planners would know that they are confronting the same virus in all of the recent outbreaks in Asia. This is another set of the many questions that need to be answered imperatively.
Pandemic preparedness activities started by WHO in the wake of the outbreaks reported earlier this year continue. Less than two weeks ago, WHO hosted a meeting in Kuala Lumpur with experts from 13 countries and areas of the Asia-Pacific region. Among other activities, the meeting participants were provided with a WHO preparedness self-assessment tool.


WHO is collaborating with scientists and the pharmaceutical community on a global surveillance system to monitor changes in the virus's susceptibility to known antivirals. Finally, pandemic vaccine development continues. Two vaccine manufacturers, both based in the United States, have produced a supply of trial vaccine which will be tested for safety and efficacy in humans.


In summary, recent developments suggest that:

? the virus is more widespread than previously thought and found in wild birds, and therefore it may be more difficult to eliminate.

? virus isolates and specimens from all recent outbreaks need to be shared with the WHO laboratory network to monitor the circulating viruses and to assess the adequacy of the current pandemic vaccine strain.

? as control measures are strengthened, national governments are encouraged to provide human influenza vaccinations to culling workers.

? all people, especially culling workers, exposed to infected birds need to be provided with antivirals.

? human trials of experimental influenza pandemic vaccines should be accelerated.

? while early identification of avian influenza cases in humans is difficult, stepped up surveillance for the early detection of the disease in humans is essential.


The risk of emergence of a new human pandemic virus will remain as long as the avian influenza virus exists in the environment. WHO's concern and activities continue at a high level following recent reports. Because the H5N1 threat is unlikely to be resolved in the shortterm, WHO is working with other international agencies, including the Food and Agricultural Organization (FAO), and World Organization for Animal Health (OIE), to monitor events.


WHO urges prompt action on avian influenza outbreaks
9 July 2004
Regional Office for the Western Pacific

http://www.who.int/csr/don/2004_07_08/en/print.html

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Avian Influenza - Necessary precautions to prevent human infection of H5N1, need for virus sharing


16 July 2004

WHO continues to be concerned by the simultaneous outbreaks of Highly Pathogenic Avian Influenza H5N1 in several Asian countries.
Avian influenza - Current evaluation of risks to humans from H5N1 following recent reports


While these outbreaks thus far remain restricted to poultry populations, they nevertheless increase the chances of virus transmission and human infection of the disease, as well as the possible emergence of a new influenza virus strain capable of sparking a global pandemic.

In this context, WHO re-emphasizes the necessity of protecting individuals involved in the culling of H5N1-infected poultry. Workers who might be exposed to H5N1-infected poultry should have proper personal protective equipment (i.e. protective clothing, masks and goggles) since there is a high risk of exposure during the slaughtering process.


In addition to the use of personal protective equipment, WHO is recommending:

To avoid the co-infection of avian and human influenza, which could allow for the emergence of a pandemic influenza virus, all persons involved in mass culling operations, transportation and burial/incineration of carcasses should be vaccinated with the current WHO-recommended influenza vaccine.
All persons exposed to infected poultry or to farms under suspicion should be under close monitoring by local health authorities. National authorities should also increase their surveillance of any reported clusters of influenza or influenza-like illness.
Antiviral treatment should be available on an on-going basis for treatment of a suspected human infection with a Highly Pathogenic Avian Influenza virus. If antivirals are available in sufficient quantities, prophylactic use should be considered.
Please see the full list of WHO's interim recommendations for the protection of persons involved in the mass slaughter of animals potentially infected with Highly Pathogenic Avian Influenza viruses.
WHO is also urging countries to work on standardized procedures for immediate sharing of all avian influenza virus strains responsible for outbreaks with WHO's international network of laboratories
WHO is depending on the continued collaboration of the national health and agricultural services to establish routine procedures for immediate sharing of avian influenza virus samples. Without such virus samples, WHO will not be in a position to provide proper vaccine prototype strains and related guidance for vaccine producers.
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Avian Influenza - Assessment of the current situation


30 July 2004

After a period of quiescence in Southeast Asia, outbreaks of highly pathogenic avian influenza (A/H5N1) are again being reported in chickens and ducks in China, Indonesia, Thailand and Viet Nam. In Thailand, outbreaks have been reported in 21 of 76 provinces; and in Viet Nam outbreaks were reported in the northern, central and southern parts of the country. These outbreaks, many without apparent epidemiological links to each other, suggest A/H5N1 is now widely prevalent and is very likely to have become endemic.


The outbreaks in birds pose a significant threat to human health.
As WHO has stated since the first A/H5N1 outbreaks were reported, this virus has the potential to ignite a global influenza pandemic in humans. In a number of these outbreaks since the beginning of 2004, the virus has jumped from infected chickens or ducks directly to humans. These direct human infections have produced severe and sometimes fatal outcomes. WHO's continuing concern is that this virus may reassort its genes with those from a human influenza virus, thereby acquiring the ability to move easily from human to human and thus triggering a pandemic.


Recent media reports have occasionally suggested the presence of new human cases of A/H5N1. WHO has received no information substantiating these reports.


At a meeting in Bangkok which ended today, the Food and Agriculture Organization (FAO), in association with the World Organization for Animal Health (OIE) and WHO, announced plans to launch a new regional veterinary influenza network. WHO welcomes this initiative as this network aims to strengthen surveillance in animals and should provide more rapid diagnosis of the disease.


The FAO/OIE regional animal laboratory network will closely link with the WHO's global influenza programme to allow for more rapid sharing of virus samples. Faster and broader sharing of samples will enable WHO to monitor for changes in the virus which could diminish the effectiveness of the human vaccine currently under development. To date, such sample exchanges have been retarded in some affected countries.


The risk of emergence of a new human pandemic virus will remain as long as the avian influenza virus exists in the environment. Without significant increase in control efforts at national and international levels, it may be years before the virus is eradicated. While these control efforts continue, WHO reemphasizes the need to monitor the health of people on these front lines. Thus, WHO-coordinated preparedness activities will continue and WHO encourages members states to start or continue with their own influenza pandemic preparedness plans.

http://www.who.int/csr/don/2004_07_30/en/print.html

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Three fatal human cases of avian influenza confirmed in Viet Nam


12 August 2004

The Ministry of Health in Viet Nam has today informed WHO that three recent deaths from influenza-like illness in Viet Nam were caused by infection with avian influenza. These are the first officially reported cases of avian influenza in Viet Nam since late February.


The three cases are among a group of patients, admitted to hospitals in Viet Nam between 19 July and 8 August, that have been under investigation by health authorities.


Initial tests have identified the virus as belonging to the H5 subtype. Further testing is needed to determine whether the virus belongs to the same H5N1 strain that caused 22 cases, with 15 deaths, in Viet Nam and 12 cases, with 8 deaths, in Thailand earlier this year.


To date, H5N1 is the only strain of the H5 subtype known to jump directly from infected poultry to cause illness in humans.


Two of the fatal cases occurred in the northern Ha Tay province. The third case occurred in the southern province of Hau Giang. Staff from the WHO country office in Viet Nam will be meeting with the Ministry of Health tomorrow to gather further details about these cases and work out plans for addressing the situation. The government has today announced an initial series of measures aimed at controlling the disease in poultry and preventing further cases in humans.


WHO regards it as particularly important that viruses from these cases be made available for further analysis by laboratories in the WHO Global Influenza Surveillance Network. Further studies can help determine whether the virus has mutated and thus yield valuable information about the further evolution of the outbreak, the risks to humans, and the best preventive measures. Studies of the virus are also important in the further development, presently under way, of an effective human vaccine.


Thorough epidemiological and clinical investigation of these cases and their contacts is needed to improve understanding of the risks to humans.
Earlier this year, Viet Nam reported outbreaks of highly pathogenic H5N1 avian influenza in poultry in 57 of the country?s 64 provinces, resulting in the death or destruction of more than 43 million poultry. After a period of quiescence, Viet Nam reported fresh outbreaks in poultry in July in provinces in northern, central, and southern parts of the country.


Outbreaks were also reported in July in China, Indonesia, and Thailand.


The confirmation of these latest human cases underscores the risk of virus transmission to humans from infected poultry. This risk will continue as long as outbreaks are occurring in poultry. Of greatest concern is the risk that continuing transmission of the virus to humans will give avian and influenza viruses an opportunity to exchange genes, potentially giving rise to a new virus with pandemic potential.

http://www.who.int/csr/don/2004_08_12/en/print.html

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Human cases of avian influenza: situation in Viet Nam


13 August 2004

More details about the three deaths from avian influenza announced yesterday are now available.


The cases in the northern Ha Tay province were a four-year-old boy, who died on 2 August, and an 11-month-old girl, who died on 4 August. The case in the southern Hau Giang province was a 25-year-old woman, who died on 6 August. Specimens from this patient have now tested positive for the H5N1 strain of avian influenza.


WHO has also been informed that specimens from a small number of additional patients, from both northern and southern parts of the country, are also being tested. The government has been investigating cases of severe pneumonia, most of which have been fatal, that have been detected in children and young adults over the past three weeks.


Specimens are not available for all of the fatal cases.


In epidemiological investigations carried out today, specimens were taken from household contacts of confirmed cases. All contacts remain healthy. Investigators have also sampled poultry and other domestic animals near the households. Results from these and other studies will shed some light on the sources of infection and modes of transmission in the present outbreak.


WHO is working closely with national authorities and is being informed as test results become available. Multiple tests are often required before results can be considered conclusive.


In its communications with the Ministry of Health, WHO has offered full assistance in sending specimens to WHO international reference laboratories for test verification and further analysis.

http://www.who.int/csr/don/2004_08_13/en/print.html

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Avian influenza ? situation in Viet Nam


18 August 2004

In the present outbreak in Viet Nam, first reported last week, three fatal human cases of avian influenza have now been laboratory confirmed, two in the north and one in the south. For two of these cases, further testing has identified the H5N1 strain as the causative agent. The most recent case died on 6 August and no new cases have been identified since then.


With support from the Ministry of Health in Viet Nam, arrangements are under way to send specimens from these cases to a laboratory in the WHO Global Influenza Surveillance Network. The laboratory will perform gene sequencing and other analyses of the virus in order to yield information immediately relevant to assessment of the public health risk.


Studies will determine whether the virus responsible for these cases has mutated. It is particularly important to learn whether the H5N1 virus strain remains entirely of avian origin.


Following a meeting held earlier this week, health officials in Viet Nam have called for close cooperation between WHO and the country?s two institutes equipped to test specimens for avian influenza. These are the National Institute of Hygiene and Epidemiology in Hanoi and the Pasteur Institute in Ho Chi Minh City. This cooperation is expected to expedite the sharing of test results on any additional cases that might require investigation.


A small team of WHO staff will be traveling to Viet Nam over the weekend. The team will be working closely with the Ministry of Health to assess the present risk to public health and to work out plans to strengthen surveillance capacity for the detection of human cases.

http://www.who.int/csr/don/2004_08_18/en/print.html

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Avian influenza: H5N1 detected in pigs in China


20 August 2004

A researcher from China?s Harbin Veterinary Research Institute has today presented initial evidence that pigs from farms in parts of China have been infected with the H5N1 strain of avian influenza. The findings, set out in a table and without further supporting data, were presented today at an international symposium on SARS and avian influenza held in Beijing.


WHO has requested confirmation and further details about this study.


Pigs are known to be susceptible to infection with avian influenza viruses. However, natural infection of pigs with the H5N1 strain has not been previously reported.


In order to assess the implications for human health, it is important to know whether the reported infections in pigs are rare events, possibly caused by contact between pigs and wild birds. Wild aquatic birds, which are the natural reservoir of all influenza A viruses, can carry the H5N1 strain without developing symptoms, and are known to excrete large quantities of the virus in their faeces.


A comparison of the H5N1 strain isolated in pigs with strains recently circulating in poultry populations in parts of Asia is needed to determine whether the virus is being passed directly from poultry to pigs. Evidence of direct transmission of H5N1 from poultry to large numbers of pigs would be of particular concern, as this would increase opportunities for a new influenza virus with pandemic potential to emerge.


Pigs have been implicated in the emergence of new influenza viruses responsible for two of the previous century?s influenza pandemics. Pigs have receptors in their respiratory tract that make them susceptible to infection with human and avian influenza viruses. If a pig is simultaneously infected with both a human and an avian influenza virus, it can serve as a ?mixing vessel?, facilitating the exchange of genetic material between the two viruses in a process known as ?reassortment?. The resulting new virus, which will not be recognized by the human immune system, will have pandemic potential if it retains sufficient human genes to allow efficient human-to-human transmission, and if it causes severe disease in humans.


Confirmation of H5N1 infection in pigs would add complexity to the epidemiology of this disease, but needs to be viewed in perspective. During the peak of the poultry outbreak of H5N1 in Viet Nam earlier this year, extensive testing of pigs on farms where poultry were heavily infected failed to find evidence of infection in pigs. In addition, Hong Kong authorities regularly perform random testing for the H5 avian influenza virus subtype in pigs imported from mainland China. No infection in pigs has been detected to date.


WHO, in collaboration with FAO and OIE, will be assessing the implications of reported H5N1 infection in pigs as further details become available.

http://www.who.int/csr/don/2004_08_20/en/print.html

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