Swine Flu

[alliecat44]

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Okay, just heard tonight that two cases of swine flu have been confirmed in Topeka, and dozens are dead in Mexico. 11 confirmed US cases in NY, CA, TX, and now KS (no fatalities so far).

I'm simultaneously excited by epidemiology in action and terrified that it's going to be like 1918 all over again. They've confirmed that it can be transmitted from person to person...looks like a pandemic is iminent.

Anyone else both fascinated and scared?

I'd love to know if the people in Mexico are dying because of poor healthcare or because it really is a virulent strain. I know it's AH1N1, which isn't supposed to be that virulent, which is why I'm a bit confused.

Also, it's been transmitted by/causing illness in young, healthy people...very, very scary.

 

[DVMorBust]

Anyone else both fascinated and scared?

Well, I went to check SDN right before going to sleep and now I've been reading all the google news hits. So yeah, I'd say me too.

 

[Pandacinny]

I think this news is SO scary! I've been reading Effect Measure blog for news on the swine flu and it's pretty good. They update frequently.

http://scienceblogs.com/effectmeasure/

There's a good NYT article that points out that the 1918 pandemic killed the young and healthy, too, but that in 1918 they didn't have ventilators or tamiflu. Still, I think it's pretty scary.

 

[Pandacinny]

As an update, they're currently testing some students and a teacher in Auckland, NZ for swine flu. They had recently traveled to Mexico. News reports are saying swine flu is likely, but test results aren't in yet.

http://www.stuff.co.nz/national/2364487/Swine-flu-likely-in-New-Zealand-teens

 

[dyachei]

I've been keeping up with it too. What I find even scarier is that 3 days ago, CNN reported on it and made no mention of the fact that it is a variant of the 1918 Spanish flu and they made it seem rather tame. Then the next day, 60 death were uncovered in Mexico with this flu associated. And from there, it keeps spreading.

But from a virology standpoint, I feel like some of my professors made a point about H1N1 maybe making a comeback.

 

[alliecat44]

Okay, type A definitely IS the pandemic-prone serotype. I was thinking it was B.

However, the H1 isn't the most virulent type--I guess that's what I was thinking. Hopefully it doesn't mutate into H5....

 

[flyhi]

Very scary indeed. I just canceled my trip to Cabo 🙁

Someone else touched on this, but why is it killing so many in Mexico, but none here yet (thank goodness)? Is it simply a matter of the type of healthcare that can be provided?

If someone had a flu shot this year, would it have any effect whatsoever on whether or not they would get this strain, or maybe even more likely, could it be a less severe case if they did come down with it?

 

[flyhi]

Anyone else think of Pupsforseeing????

 

[VAgirl]

Situation reports from WHO:
http://www.who.int/csr/don/2009_04_24/en/index.html
http://www.who.int/csr/don/2009_04_26/en/index.html

Information sheet from WHO:
http://www.who.int/csr/swine_flu/swine_flu_faq_26april.pdf

 

[VAgirl]

Someone else touched on this, but why is it killing so many in Mexico, but none here yet (thank goodness)? Is it simply a matter of the type of healthcare that can be provided?

Could very easily be linked to quality of health care. That's a common issue, the lack of supportive care.

If someone had a flu shot this year, would it have any effect whatsoever on whether or not they would get this strain, or maybe even more likely, could it be a less severe case if they did come down with it?

From CDC (http://www.cdc.gov/flu/flu_vaccine_updates.htm#protection)
"The flu vaccine protects against the three main flu strains that research indicates will cause the most illness during the flu season. This year's influenza vaccine contains three new influenza virus strains.
They are:

• A/Brisbane/59/2007(H1N1)-like virus;
• A/Brisbane/10/2007 (H3N2)-like virus;
• B/Florida/4/2006-like virus."

So it looks like one of the strains in the vaccine this year was an H1N1. There are lots of different H1s and N1s, so it's not a guarantee, but it could help provide some immunity and could help lessen the severity of infection, as I understand it.

 

[VAgirl]

However, the H1 isn't the most virulent type--I guess that's what I was thinking. Hopefully it doesn't mutate into H5....

An H1 can't really mutate into an H5. However one of the big concerns with influenza infections in pigs, generally, is that they can have co-infection with 2 different influenza strains. If that happens, there can be reassortment within the pig of the influenza viruses of the hemagglutinins and neuraminidases. In other words, you could have an H1N1 and H2N2 go in, and could get back out an H1N2 and H2N1. (Just using random Hs and Ns...not sure what species H2N2s might infect.)

But not all H1s and N1s are the same, there are high pathogenic and low pathogenic influenza strains, even with the same hemagglutinins and neuraminidases. So it's hard to say what a reassortment event would mean.

 

[alliecat44]

I read somewhere that this year's flu vaccine doesn't confer any meaningful immunity to this virus. Can't cite the source, as it was in a couple of the many articles I read. 🙂 VAGirl would know more--I just know what I've studied in virology.

Also, it seems that Mexico was seeing a spike in flu cases in March. At the time, they chalked it up to a late-winter "rebound" and didn't become too concerned until the first victim died April 13. It then took until April 18 for them to send samples to the CDC. So, looks like it probably was around in March, exposing who knows how many people. Hopefully all those exposed have now recovered--but I would doubt any assertion that we know about all the deaths this virus has caused so far.

Officials are saying the mortality is likely because people didn't seek medical care in time--so that's good. Awareness is a positive thing! Yay for modern medicine and communication systems.

VAGirl, to my mind, I would think it would be a much riskier proposition if it made its way to Asia and recombined with an H5 variant. Looks like you addressed that while I was posting!
Here's hoping it'll burn itself out soon...

 

[alliecat44]

An H1 can't really mutate into an H5. However one of the big concerns with influenza infections in pigs, generally, is that they can have co-infection with 2 different influenza strains. If that happens, there can be reassortment within the pig of the influenza viruses of the hemagglutinins and neuraminidases. In other words, you could have an H1N1 and H2N2 go in, and could get back out an H1N2 and H2N1. (Just using random Hs and Ns...not sure what species H2N2s might infect.)

But not all H1s and N1s are the same, there are high pathogenic and low pathogenic influenza strains, even with the same hemagglutinins and neuraminidases. So it's hard to say what a reassortment event would mean.

I guess what I'm worried about is a recombination event. I think the A/B/C designation is really what describes species susceptibility--I imagine there are H2N2s that do and don't infect humans. Type A flu viruses can infect birds/people/pigs/mink/even whales.

Since genetic reassortment is common and that's how we got this variant...I guess my big question is what if this goes to Asia, reassorts in a mixing vessel (such as a pig!) and we get an H5 or H7 strain...that would be SCARY. The H5 and H7s are the most virulent. Really hope we don't get antigenic shift!!

 

[VAgirl]

I read somewhere that this year's flu vaccine doesn't confer any meaningful immunity to this virus. Can't cite the source, as it was in a couple of the many articles I read. 🙂 VAGirl would know more--I just know what I've studied in virology.

Oh goodness, I definitely don't know more! 😳 If experts are saying there's no meaningful immunity to this H1N1 strain from this year's vaccine, then that's what we should listen to, certainly. Theoretically, there was a chance because of the H1N1 like strain in the vaccine, but like I said, not all H1s and N1s are the same. That's too bad, though.

VAGirl, to my mind, I would think it would be a much riskier proposition if it made its way to Asia and recombined with an H5 variant. Any thoughts on how likely this is?

Absolutely no idea. 😛 Though I'm curious what's going on at my old job with all this stuff afoot!

The one thing I will say on the H5N1 situation in Asia is that, last time I checked (not very recently), the big thing keeping H5N1 from being a significant human problem was the lack of sustained human to human transmission. Certainly if that H5N1 strain mutated or reassorted with a more transmissible influenza virus, then it could become the human health problem we've been fearing. But it seems hard to imagine that these two issues (H1N1 swine flu in the Americas and H5N1 bird flu in Asia) would influence or interact with each other. (But there I go speculating...so who knows.)

The most encouraging thing so far, I think, is that there haven't been anything but reports of mild illness in the US. So probably no need to start panicking yet!

 

[twelvetigers]

Anyone else think of Pupsforseeing????

I hadn't, but I certainly am now! I hope she is okay. 🙁

 

[nlax30]

I read somewhere that this year's flu vaccine doesn't confer any meaningful immunity to this virus. Can't cite the source, as it was in a couple of the many articles I read. 🙂 VAGirl would know more--I just know what I've studied in virology.

It's been in a few of the CDC publications/press releases:

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

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 and, therefore, vaccines for human seasonal flu would not provide protection from H1N1 swine flu viruses.

 

[BR549]

Yeah, I've been keeping up with it as well. Epidemiology has always interested me. I find this very interesting, as I just finished up a workshop at the CDC in Atlanta and they gave us a tour of the Emergency Operations facility, where they would have everyone from the different disciplines come together in case of an emergency. They had a huge wall with about 10 flat screen T.V.'s, one of which kept track of disease outbreaks around the world. I bet Mexico is lit up now.

 

[cozycleo]

Yeah, I've been keeping up with it as well. Epidemiology has always interested me. I find this very interesting, as I just finished up a workshop at the CDC in Atlanta and they gave us a tour of the Emergency Operations facility, where they would have everyone from the different disciplines come together in case of an emergency. They had a huge wall with about 10 flat screen T.V.'s, one of which kept track of disease outbreaks around the world. I bet Mexico is lit up now.

Ok I'm incredibly jealous. 🙂

This is the area I'm interested in as well, so I've been watching closely.

 

[critterfixer]

Hmm.. it seems the reaction of the media is a bit overblown at this point, IMO. I think one of the reasons this has caused death in Mexico, but not here (yet, anyway) is because of the simple fact we are more apt to wash our hands frequently. Hygiene, overall, plays a huge role in the spread of many viruses.

Considering that the "typical" flu season ends with something around 40,000 deaths per year in the USA, I am not ready to get excited about such small numbers. Pay attention, diligently wash hands, be considerate and don't show up for work or school if you are actively spreading a virus and request other people who are sick with a respiratory virus to do the same.

Sure it's scary to think this could be something epic, but at this point, it's pretty small potatoes in comparison to a normal influenza season, and most people don't give that much thought at all. Influenza rates are actually declining per the CDC, even with the swine flu variant: http://www.cdc.gov/flu/weekly/

 

[TSUJC]

Hmm.. it seems the reaction of the media is a bit overblown at this point, IMO.

Considering that the "typical" flu season ends with something around 40,000 deaths per year in the USA, I am not ready to get excited about such small numbers. Pay attention, diligently wash hands, be considerate and don't show up for work or school if you are actively spreading a virus and request other people who are sick with a respiratory virus to do the same.

I strongly agree!

 

[alliecat44]

This TYPE of flu (H1N1) has been around for ages. Usually, though, most H1N1s are transmitted sporadically between pigs and people (usually farmers or veterinarians)--a few cases a year.

What makes this concerning is its transmission factor, not the virulence/death rate. For the first time since the pandemics of 1918 and 1957 (I think), an H1N1 can be transmitted easily from person to person. THAT is what is concerning--all that needs to happen is some genetic recombination to increase the virulence and voila...a perfect storm, as it were. The fact that it's killing young healthy people is also reminiscent of the 1918 outbreak.

 

[Fairyblastt]

Probably a rehash of what everybody has already read, but here's what was in my inbox yesterday. It's from the ProMED Digest, vol: 2009, # 191.

Date: 25 Apr 2009
Source: Peter Cowen, ProMED-mail Animal Disease Moderator


Since we have a great deal of experience with confusing terminology when a disease occurs at the human/animal interface, I thought a few comments on the current H1N1 situation were warranted. For example, one might argue
that the zoonotic disease, eastern equine encephalitis is not very aptly named. Horses are a dead end host, wild birds are the zoonotic reservoir, and poultry flocks serve as sentinel sites for surveillance and indicators of when to begin mosquito control. Moreover, the disease occurs in people
on both the East Coast and Gulf Coast of the United States. Very little of this epidemiology could be deduced from the name, eastern equine encephalitis. With that as a preamble, let me make some comments concerning the terminology in common use -- swine flu -- for our present outbreak.

In the first place, the H1N1 virus is being called "swine flu" because of the outbreak of a different, 1918 origin virus that caused significant mortality in both swine and human populations and was known as the Spanish flu. The virus probably has a wild bird origin but it definitive origin remains unknown (see Taubenberg reference below).

The subsequent history of the swine influenza virus is nicely summarized: "Influenza as a disease of pigs was 1st recognized during the Spanish influenza pandemic of 1918-1919. Veterinarian J S Koen was the 1st to describe the illness, observing frequent outbreaks of influenza in families followed immediately by illness in their swine herds, and vice versa [1]. Influenza virus was 1st isolated from pigs in 1930 by Shope and Lewis [2], with the virus isolated from humans several years later [3]. The 1st
isolation of a swine influenza virus from a human occurred in 1974 [4], confirming speculation that swine-origin influenza viruses could infect humans." See Myers below.

In the second place, influenza viruses regularly circulate in swine populations and include H1N1, H3N2, H1N2, H1N3 most commonly, with almost 25 per cent of more than 114 000 swine serum samples in the US being positive for one of the serotypes (see Choi et al. Arch Virol 2002 Jun;
147(6): 1209-20). As such, it is well controlled in swine populations, even though it can cause concern on particular farms that don't manage well for its occurrence or at particular times.

Then, thirdly, swine flu viruses have been known to infect humans -- 50 cases were turned up from an extensive review of the literature. Of the non-military cases, 19 occurred in the United States, 6 in Czechoslovakia, 4 in the Netherlands, 3 in Russia, and 1 each in Canada and Hong Kong. Most (61 per cent) of the cases studied had reported an exposure to swine and the median age was 24 years (see Myers below). The most recognizable H1N1 transmission event involved 12 soldiers at Fort Dix in 1976, one of whom died. Contact with swine was never established. Another important transmission resulted in the death of a pregnant woman, who was exposed to pigs, in 1988 in Wisconsin.

Finally, it appears as if no exposure to swine has occurred among people who have come down with the current novel H1N1 virus. The virus has elements of human, swine, and avian viruses normally found in Europe or Asia. It is this genetic analysis of the virus which has really developed the level of concern for this outbreak. If there wasn't a match with the US virus the fact that it is being transmitted out of season and in young, healthy adults might have even been overlooked.

So, in summary, the reason that we are calling this virus swine flu is the history and evolution of the virus. It also rests on the fact that some of the genetic analysis indicates that elements from viruses that have traditionally been found in swine populations are incorporated. However since we know nothing of how this particular virus has gotten into the
human population but there apparently is no history of swine exposure, it probably makes more sense epidemiologically to refer to this simply as an H1N1 influenza virus.

To some extent a similar nomenclatural history has occurred over time with the H5N1 virus becoming known by its viral strain, rather than bird flu. At least with the H5N1 it can most often be traced to exposure to avian species. But in the case of this so called swine flu, there really does appear to be no exposure to swine and some evidence (father, daughter pair in the US) of transmission without exposure to animals. Realistically, however, the name seems to have stuck in the popular media already and the terms swine flu does reflect what we know about the history of some very important H1N1 viruses. Unfortunately, this name will imply a simple,
zoonotic transmission between swine and people, when in reality is origin and epidemiology is liking to be much more complex. Therefore, good epidemiologic studies in swine in Mexico could be very helpful in understanding this apparently new virus.

References
- ----------
1. Taubenberger JK, Morens DM. 1918 influenza: the mother of all pandemics.
Emerg Infect Dis [serial on the Internet]. 2006 Jan [date cited]. Available
from <http://www.cdc.gov/ncidod/EID/vol12no01/05-0979.htm>.
2. Myers KP, Olsen CW, Gray GC. Cases of swine influenza in humans: a
review of the literature. Clin Infect Dis 2007; 44: 1084-8 doi: 10.1086/512813.

- --
communicated by:
ProMED-mail
<[email protected]>

 

[Fairyblastt]

Another from the same digest.

[2] Comments on swine, poultry exposure
Date: 25 Apr 2009
Source: Barrett Slenning
Animal Biosecurity Risk Management Group
College of Veterinary Medicine, North Carolina State University
<[email protected]>


[I find Barrett Slenning to be unusually thoughtful on matters of disaster preparedness as it relates to agriculture and zoonotic diseases, so here are some comments he put together as a summary explanation for animal producers from last night (24 Apr 2009) here in North America. - Mod.PC]

We are dealing with an H1N1 swine-associated type A influenza that carries both human and avian characteristics. It is a novel virus that had not been described previously. It appears to be resistant to some antivirals, but sensitive to Tamiflu and similar drugs.

Human cases from this virus emerged nearly simultaneously in the border counties (San Diego and Imperial counties) of California (27 Mar 2009) and in north-central Mexico (22 Mar 2009). The news reporting out of Mexico is not consistent, and I am not privy to the official consultations between
the 2 countries, but it appears the Mexican outbreak is in the Mexico City area (south central Mexico), the sectors in and around San Luis Potosi (about 400 miles north of Mexico City), and in Mexicali (on the border with Calexico in Imperial county California).

To date, 8 cases in the US have been documented, all of whom recovered/are recovering (only one was hospitalized and that was an immunocompromised individual with other disease issues). There are over 900 cases in Mexico, with over 60 fatalities (approx 6 per cent case fatality rate). Why the
disparity in severity between the 2 countries is unknown, but with the US numbers being so low, it could just be a luck of the draw kind of thing right now: my back of the envelope calculations suggest that if the US had the same base case fatality rate as in Mexico, the likelihood we could have 8 cases without a death is nearly 60 per cent.

None of the US cases have any known exposures to either swine or poultry. To date, though epidemiologic trace backs are far from complete, none of the Mexican cases have swine or poultry exposures either. There are a couple of apparent family clusters in Mexico, so with that evidence and no
recognized pig/bird exposures, it appears that we are seeing human to human transmission.

We do not know if this virus is circulating in swine populations. We have no evidence of it in domestic swine, although the industry does not have the depth of influenza surveillance that we see in poultry, and there is some doubt that this new H1N1 strain would be identified as unusual with
standard tests anyway. Groups are doing rapid assessments right now, so that information may change momentarily as data come in. Feral swine are another possible source/reservoir, but we have no information on them. I do not know if anyone is currently chasing the potential of this virus to be
in birds.

Nobody knows right now where we are in the epidemic -- if this will burn itself out in a few weeks or not. It is nearing the end of the influenza season, so that is on our side. However, there are historical precedents that should give us pause:

1. It was an H1N1 directly from birds that caused the 1918 pandemic that killed more people than all the wars in the 20th century combined;
2. The 1st cases of that agent showed up in May 1918 in an army base in Kansas -- it went quiet over the summer -- and started ravaging the globe in early fall that year.

- --
communicated by:
ProMED-mail
<[email protected]>

 

[critterfixer]

In 1918 they did not have antiviral drugs. This virus has shown susceptibility to two different antiviral medications. I still say this is not nearly as alarming as the media would like us to think it is.

 

[bunnity]

Haha we just got an email at work (people hospital) to the effect of:

Your ass better show up to work if the swine flu comes here, unless you have it yourself!

 

[hopefulvet21]

A girl who is a hostess at the restaurant I waitress at has it! She lives in Queens and was one of the 8 confirmed cases of 'swine' flu at St. Francis Prep. Great...all I need is swine flu during finals! She is fine though, she's not in the hospital or anything. I think the whole deal has been blown out of proportion by the media.

The reason that pigs are susceptible to more strains of flu is because they have both the alpha-2,6 sialic acid linkage to galactose in respiratory epithelia and the alpha-2,3 sialic acid linkage in intestinal cells (the surface receptors for influenza, also a molecule that the virus must cleave to exit the cell). When birds are afflicted with influenza, the virus infects through the intestines (they only have the 2,3 linkage), whereas in humans it is through the oropharynx. I think the avian influenza outbreak was considered more of a threat than it was. It was highly pathogenic and had a 60% mortality rate, but my Virology prof. also told us that those infected were discovered to have a genetic susceptibility to the virus. Antigenic shift could occur, but I'd say it's unlikely.

 

[DollyyLlama]

you guys are blinding me with science! 🙂

 

[DrVegan]

its both...fascinating and scary.