Swine flu worse in Mexico than US, but why?

[Forelle]

Re: Swine flu worse in Mexico than US, but why?

I somehow believe that the immune system of a Mexican is maybe less prepared for such a subtype of virus than that of someone from the US. I was told that the influenza vaccine in Europe won't protect much from influenza in Latin America. The same about the vaccine from the US. So, that could be an explanation, why the virus could even kill in Mexico, whereas it "just" made people feel sick in the US. What do you think?

 

[flutrackers@cool.fr.nf]

Re: Swine flu worse in Mexico than US, but why?

I somehow believe that the immune system of a Mexican is maybe less prepared for such a subtype of virus than that of someone from the US. I was told that the influenza vaccine in Europe won't protect much from influenza in Latin America. The same about the vaccine from the US. So, that could be an explanation, why the virus could even kill in Mexico, whereas it "just" made people feel sick in the US. What do you think?

I dont really think so. The fact that we have been vaccinated and exposed to more in the USA does not really change much. Many people in Mexico have been exposed to most of the same flus we have in the USA. And generally with seasonal flus it does not make much of a difference, so I doubt it would in this case. Plus if concerns are accurate and its a virus as virtulent as the 1918 virus it wouldnt make any difference at all.

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

I somehow believe that the immune system of a Mexican is maybe less prepared for such a subtype of virus than that of someone from the US. I was told that the influenza vaccine in Europe won't protect much from influenza in Latin America. The same about the vaccine from the US. So, that could be an explanation, why the virus could even kill in Mexico, whereas it "just" made people feel sick in the US. What do you think?

Read the "sequences at genbank" thread, starting with post #9. Then remember the many homes in Mexico City without good sanitation facilities.

Then we need to think of what will happen if/when this flu gets to jakarta, mumbai, bangladesh, cairo, etc. Hopefully, being forewarned will change the results in those areas.

.

 

[ldaziens]

Re: Swine flu worse in Mexico than US, but why?

A serious lack of potable water may also be a factor that could effect health and sanitation. Please note the article is dated April 11th.


Dry Taps in Mexico City: A Water Crisis Gets Worse
Time.com
By IOAN GRILLO / MEXICO CITY Ioan Grillo / Mexico City ? Sat Apr 11, 1:40 am ET

"The reek of unwashed toilets spilled into the street in the neighborhood of unpainted cinder block houses. Out on the main road, hundreds of residents banged plastic buckets and blocked the path of irate drivers while children scoured the surrounding area for government trucks.
......

About five million people, or a quarter of the population of Mexico City's urban sprawl, woke up Thursday with dry taps. The drought was caused by the biggest stoppage in the city's main reservoir system in recent years to ration its depleting supplies."

Link to entire article:
http://news.yahoo.com/s/time/20090411/wl_time/08599189062300

Don't you think that this water shut off helped this flu gain momentum -- if only because 5 million people weren't washing their hands. I read an MSNBC story, http://www.msnbc.msn.com/id/28967672/, saying that the water was shut off for 3 days and would be shut off for 3 days on a monthly basis. PLEASE tell me they are not going to shut it off again in the midst of this mess!

 

[Laidback Al]

Re: Swine flu worse in Mexico than US, but why?

Welcome to FluTrackers, ldaziens.

Your question about continuing the planned 3-day water conservation stoppage in Mexico City is a good one. The fact that a local epidemic has developed, and could be somewhat ameliorated by having additional water supplies, does not change the fact that the city only has a limited water supply to take it into the start of the rainy season next month.

The Mexico city planners have a difficult task of determining how to best distribute the limited amounts of water in the reservoirs to minimize both disease and hardship in the metropolitan area.

 

[Niko]

Re: Swine flu worse in Mexico than US, but why?

Newbie here. Is there any estimate of the incubation period for this flu? How long between a potential exposure and the onset of symptoms?

One of my co-workers traveled to Mexico two weeks ago and returned with flu-like symptoms (worst he has been sick in years). We thought nothing of it at the time, and we have no idea if it was swine flu or something more pedestrian, but we can't help trying to calculate when we are "all clear" from any chance of contraction. Although I assumed it would be widely broadcast information, I am having trouble finding any estimates of the incubation period of this strain.

Thanks in advance for any help.

According to the CDC (USA)...

"Infectious Period

Persons with swine influenza A (H1N1) virus infection should be considered potentially contagious for up to 7 days following illness onset. Persons who continue to be ill longer than 7 days after illness onset should be considered potentially contagious until symptoms have resolved. Children, especially younger children, might potentially be contagious for longer periods. The duration of infectiousness might vary by swine influenza A (H1N1) virus strain.

Non-hospitalized ill persons who are a confirmed or suspected case of swine influenza A (H1N1) virus infection are recommended to stay at home (voluntary isolation) for at least the first 7 days after illness onset except to seek medical care."

http://www.cdc.gov/swineflu/guidelines_infection_control.htm

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

Welcome to FluTrackers, ldaziens.

Your question about continuing the planned 3-day water conservation stoppage in Mexico City is a good one. The fact that a local epidemic has developed, and could be somewhat ameliorated by having additional water supplies, does not change the fact that the city only has a limited water supply to take it into the start of the rainy season next month.

The Mexico city planners have a difficult task of determining how to best distribute the limited amounts of water in the reservoirs to minimize both disease and hardship in the metropolitan area.

they could try distributing hand gel for use during those 3 days. However, if you know you won't have water for 3 days, the normal action would be to store water. It may be that the general difficult of getting enough water for showers and adequate cleaning also contributes to the problems.

.

 

[Forelle]

Re: Swine flu worse in Mexico than US, but why?

We actually did store water, bought bottled water, and the water supply, at least in our area, wasn't stopped throughout the 3 days, but mainly during the nights only. As far as I know, the water supply system is regularly repaired around Easter time (the reparations should be finished by now). Surely hygiene isn't the best in Mexico, but that wouldn't explain the death cases from my point of view, particularly in Mexico City or even in a hospital.

 

[ldaziens]

Re: Swine flu worse in Mexico than US, but why?

We actually did store water, bought bottled water, and the water supply, at least in our area, wasn't stopped throughout the 3 days, but mainly during the nights only. As far as I know, the water supply system is regularly repaired around Easter time (the reparations should be finished by now). Surely hygiene isn't the best in Mexico, but that wouldn't explain the death cases from my point of view, particularly in Mexico City or even in a hospital.

I am glad to hear that the water was only shut off at night. That seems like a sensible way to handle the shortage. The news articles made it sound like there was zero water for 3 days and no one was prepared, so thanks for clarifying. Sadly, it's not a huge surprise that our news is less than accurate.

And I'm sure that you are right that a lack of handwashing wouldn't make an individual case worse per se, but isn't there a concern that the more the virus spreads, the worse it can get? I am a teacher, not a medical expert, so I am not sure of the terminology.

It seems that here in the U.S. the virus is impacting school age kids more with usually "mild" results. I am wondering if kids in Mexico were the initial "mild" carriers but aren't documented. It seems like neither Mexico nor the US are trying to track mild cases. The guidance I have read here tells people to stay at home unless they experience difficulty breathing or other serious symptoms, so those individuals w/ mild syptoms wouldn't be tested, right? On the one hand that makes total sense -- why tie up a health care provider and potentially spread the virus to others. However, I don't understand how the experts can realistically track or model this outbreak without knowing how many people get sick when exposed and the degree of the illness.

The NY School outbreak seems like a good opportunity to test all students and close contacts to get a sense of that. Schools are definitely petri dishes and most students are not good handwashers and love to put their hands all over their faces, so I would think it would be good to study that small population.

Lastly, my understanding is that some of the NYC school kids spent Spring Break in Cancun, but I didn't see any swine flu cases listed in the Riviera Maya area. Maybe their flight went through Mexico City, but I would think they would have been on a direct flight between NYC & Cancun.

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

However, I don't understand how the experts can realistically track or model this outbreak without knowing how many people get sick when exposed and the degree of the illness.

I think accurate numbers can only come from a confined population then you know who did/did not get sick out of the total - nobody is missed. So when a prison, military base, assisted living home, etc. gets infected, we may get truly accurate numbers.

some of the NYC school kids spent Spring Break in Cancun, but I didn't see any swine flu cases listed in the Riviera Maya area.

Seasonal food service workers could come from anywhere in Mexico for a short employment opportunity. Almost ill or recovering ill labor force may not be receiving medical care while they provide labor for spring break business.

This looks like it might be highly contact spread - see sequences thread.

.

 

[Farmer]

Re: Swine flu worse in Mexico than US, but why?

I think accurate numbers can only come from a confined population then you know who did/did not get sick out of the total - nobody is missed. So when a prison, military base, assisted living home, etc. gets infected, we may get truly accurate numbers.

...

.

I understand the attraction and simplicity of having 100% ascertainment of illness among a defined group of people. However, this approach does not neccesarily produce a good estimate of the CFR for the outbreak as a whole.

The well-defined groups given as examples here could all be characterized as living in crowded conditions, and some may be more susceptible to infection because of age or underlying health characteristics.

Calculating an overall CFR for an outbreak is never perfect, may change as the outbreak evolves, and is done somewhat in retrospect. We may be led astray if we try to extrapolate rates calculated in an artificially crowded group to a general population.

 

[wetDirt]

Re: Swine flu worse in Mexico than US, but why?

Here is an hypothesis: if surface transmission is more important than airborne for this version of the virus, then there will be gender differences in numbers cases or severe cases. Airborne is nonselective, but there are liable to be statistical differences between genders in handwashing, restroom cleanliness, and so forth.

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

I understand the attraction and simplicity of having 100% ascertainment of illness among a defined group of people. However, this approach does not neccesarily produce a good estimate of the CFR for the outbreak as a whole.

The well-defined groups given as examples here could all be characterized as living in crowded conditions, and some may be more susceptible to infection because of age or underlying health characteristics.

Calculating an overall CFR for an outbreak is never perfect, may change as the outbreak evolves, and is done somewhat in retrospect. We may be led astray if we try to extrapolate rates calculated in an artificially crowded group to a general population.

My comments were not intended to point to a group, but rather looking for a set of conditions, which could occur anywhere to anyone. CFR is not attainable at this point, but looking for conditions leading to mortality is a worthwhile activity. Refusal to make any group references to the point where we stop looking for the truth is also a deadly disease. It could be something simple, like there are a few "superspreaders" that are continuing to infect - combine influenza, HIV, TB. That potential can occur in many places among any group.

.

 

[Forelle]

Re: Swine flu worse in Mexico than US, but why?

I couldn't find the "sequences at genbank" thread... Is it understandable for a layman?

 

[genesisair]

Re: Swine flu worse in Mexico than US, but why?

Source: http://www.google.com/hostednews/ap/article/ALeqM5isJD5Q4PP0jfBREmcu5au3Cdr2EAD97PPGU00


"The question of why the virus appears to be more virulent in Mexico is one that we are looking intensively into," the CDC's Schuchat said. "Rather than speculate, it's important for the science to lead us on this."

"Here is an excerpt out of a paper that might explain this question.
Humans acutely infected with influenza A virus have a high virus titer in their respiratory secretions, which will be aerosolized when the
patient sneezes or coughs. The viral titer measured in nasopharyngeal washes culminates on approximately day 2 or 3 after infection and
can reach up to 107 50% tissue culture infective dose (TCID50)/mL.[13,14] The persistence of the infectivity of influenza virus in aerosols has
been studied in the laboratory. In experiments that used homogeneous aerosolized influenza virus suspensions (mean diameter 6 μm),
virus infectivity (assessed by in vitro culture) at a fixed relative humidity undergoes an exponential decay; this decay is characterized by
very low death rate constants, provided that the relative humidity was in the low range of 15%--40%.[15,16] These results are consistent with
those of an older study (admittedly performed in a more rudimentary manner) in which infectious influenza viruses in an aerosol could be
demonstrated for up to 24 h by using infection in mice as a detection method, provided that the relative humidity was 17%-24%.[17] In all
these studies, the decay of virus infectivity increased rapidly at relative humidity >40%. The increased survival of influenza virus in
aerosols at low relative humidity has been suggested as a factor that accounts for the seasonality of influenza.[15,16] The sharply increased
decay of infectivity at high humidity has also been observed for other enveloped viruses (e.g., measles virus); in contrast, exactly the
opposite relationship has been shown for some nonenveloped viruses (e.g., poliovirus).[11,15,16]"
From Emerging Infectious Diseases
Review of Aerosol Transmission of Influenza A Virus
Raymond Tellier
Published: 11/30/2006

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

I couldn't find the "sequences at genbank" thread... Is it understandable for a layman?

try: http://www.flutrackers.com/forum/showthread.php?t=101112

Understandable? I've been trying for 4 years and still have to muddle my way through, but FT posters do their best to make it understandable.

.

 

[AlaskaDenise]

Re: Swine flu worse in Mexico than US, but why?

"Here is an excerpt out of a paper that might explain this question.
Humans acutely infected with influenza A virus have a high virus titer in their respiratory secretions, which will be aerosolized when the
patient sneezes or coughs. The viral titer measured in nasopharyngeal washes culminates on approximately day 2 or 3 after infection and
can reach up to 107 50% tissue culture infective dose (TCID50)/mL.[13,14] The persistence of the infectivity of influenza virus in aerosols has
been studied in the laboratory. In experiments that used homogeneous aerosolized influenza virus suspensions (mean diameter 6 μm),
virus infectivity (assessed by in vitro culture) at a fixed relative humidity undergoes an exponential decay; this decay is characterized by
very low death rate constants, provided that the relative humidity was in the low range of 15%--40%.[15,16] These results are consistent with
those of an older study (admittedly performed in a more rudimentary manner) in which infectious influenza viruses in an aerosol could be
demonstrated for up to 24 h by using infection in mice as a detection method, provided that the relative humidity was 17%-24%.[17] In all
these studies, the decay of virus infectivity increased rapidly at relative humidity >40%. The increased survival of influenza virus in
aerosols at low relative humidity has been suggested as a factor that accounts for the seasonality of influenza.[15,16] The sharply increased
decay of infectivity at high humidity has also been observed for other enveloped viruses (e.g., measles virus); in contrast, exactly the
opposite relationship has been shown for some nonenveloped viruses (e.g., poliovirus).[11,15,16]"
From Emerging Infectious Diseases
Review of Aerosol Transmission of Influenza A Virus
Raymond Tellier
Published: 11/30/2006

Could you post the link. thanks.

Also see "sequences at genbank" thread - PB2/627 in the 10M from san Diego is set to NOT allow this virus to replicate well in the human respiratory system, so some of the normal observations mentioned above may not apply 100%.

.

 

[genesisair]

Re: Swine flu worse in Mexico than US, but why?

http://www.medscape.com/viewarticle/546777

 

[cartski]

Re: Swine flu worse in Mexico than US, but why?

http://www.medscape.com/viewarticle/546777

Subscription required.

Perhaps this is the same thing?

Emerg Infect Dis. 2006 Nov;12(11):1657-62. Links

Emerg Infect Dis. 2007 Jan;13(1):173-4; author reply 174-5.
Review of aerosol transmission of influenza A virus.Tellier R.
Division of Microbiology, Hospital for Sick Children, Toronto, Ontario, Canada raymond.tellier@sickkids.ca

In theory, influenza viruses can be transmitted through aerosols, large droplets, or direct contact with secretions (or fomites). These 3 modes are not mutually exclusive. Published findings that support the occurrence of aerosol transmission were reviewed to assess the importance of this mode of transmission. Published evidence indicates that aerosol transmission of influenza can be an important mode of transmission, which has obvious implications for pandemic influenza planning and in particular for recommendations about the use of N95 respirators as part of personal protective equipment.

PMID: 17283614 [PubMed - indexed for MEDLINE]

Full article: http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm

 

[cartski]

Re: Swine flu worse in Mexico than US, but why?

So, what then has been the recent history of humidity levels in Mexico?

And how would altitude affect droplet transmission at certain humidity levels?

But this has to do with transmission, not the severity of the outcome after contracting the disease.

We're still faced with why people in Mexico are dying, but people elsewhere are not.

J.