More spillover flu cases...2 cats in Canada

A few news articles have reported infection of two cats with the H1N1 flu virus. These are the first feline cases reported in Canada, but similar cases have been reported elsewhere, so it’s reasonable to assume that there have been previous undiagnosed feline cases in Canada. Nevertheless, it’s useful information.

Unfortunately, the new reports are very minimalistic in their details - not quite "cat-flu-dead" but pretty close. Information like what clinical signs the cats had, whether there were infected people in the household first, how infection was diagnosed and how the virus strain was confirmed would be useful.

Cases like this always raise a few questions:

What’s the risk to people in the household?

  • Pretty limited. We don’t know if infected cats are able to spread the H1N1 virus (though we know that cats experimentally infected with the H5N1 flu shed enough virus that they could pose a risk).
  • Nonetheless, it’s important to consider the household disease dynamics. From where did the cat get H1N1? From a person. With what people do most cats almost exclusively have contact? People in the household. So, if the cat was infected, it was probably infected by someone in the household or someone who visited the household, both of which pose a greater risk to other people in the household than the cat.

What’s the risk to the cat population?

  • Pretty limited for a few reasons. Most cats don’t tend to have contact with that many cats outside of the household, and the flu virus is shed for a short period of time.
  • Cats are also not very susceptible to the virus, so an infected cat would have to be shedding appreciable amounts of virus, have an encounter with a susceptible cat during the short time it’s shedding virus, and then this low-likelihood scenario would have to repeat itself in order for the virus to establish itself in the cat population.

Can cats be a source of new flu viruses?

  • In the big picture, this is the main concern. Any species that can be a host for a human flu virus and other flu viruses is a concern because of the potential that infection with multiple viruses at the same time could lead to creation of a new virus - one that is still able to infect people, but is different enough that people don’t have any immunity and current vaccines don’t work (which means it could potentially make a lot of people sick very rapidly).
  • However, the risk of this scenario is exceedingly low in cats since H1N1 infection in this species is very rare, and infection of cats by other flu viruses is ever more rare.  Therefore, the odds of concurrent infection AND reassortment of the viruses AND transmission to a susceptible host that can further spread the virus is are extremely remote.

2009 feline H1N1 case published

When the novel H1N1 influenza pandemic infected large numbers of people, it was not particularly surprising that the occasional infection was noted in pets, considering over 50% of North American households have pets, and the close nature of contact that many people have with their pets. While the few cases that occurred were highly publicized, in the end pet infections were rarely diagnosed (although that doesn't mean they were truly rare), and limited information about these cases has been available. Details regarding one H1N1-infected cat from Iowa (Sponseller et al. 2010) were recently published in Emerging Infectious Diseases.

Here are some of the highlights:

  • The 13-year-old cat was an indoor cat that was admitted to Iowa State University's veterinary hospital because of depression, decreased appetite and signs of respiratory disease.
  • Two of 3 people in the house had undiagnosed influenza-like illness a few days before the cat got sick. The cat was an affectionate pet and interacted closely with household members.
  • Influenza was diagnosed in the cat by detection of H1N1 influenza virus using molecular diagnostic methods (reverse transcriptase PCR) on a sample of fluid collected from the lungs.
  • The cat improved with supportive care alone (mainly intravenous fluids to correct dehydration).

Considering the cat lived indoors and people in the house had signs consistent with influenza, it's almost certain that the cat was infected by its owners. This isn't surprising, but it's a good example of how infectious diseases can move between people and pets, in either direction. There's no evidence that pets were a source of human infection, but if something can move from people to pets, there's certainly good reason to think that it could go back from pets to other people. This should be another wake-up call for the need to consider and investigate the potential role of pets in any emerging infectious disease, and to consider emerging "human" diseases in sick animals that might have been exposed.

H1N1 in a dog

H1N1 influenza was diagnosed in two dogs in China, bringing increased calls to pay attention to other animal species when it comes to this disease.

I'm more surprised by this than finding H1N1 in a cat or ferret. Dogs are susceptible to influenza and have their own circulating influenza strain (H3N8, originally from horses) but they rarely get other types of influenza. It's just an example of "rare things happen rarely, but they do happen." As with cats, it is now apparent that dogs are susceptible to this virus, although presumably minimally susceptible given the very low incidence of reported canine infections. This doesn't change our basic recommendations for dealing with H1N1: infected people should reduce contact with all individuals in the household, human or otherwise. People should be aware but not worried about the potential for pets to acquire H1N1. The risk of animals transmitting H1N1 back to people is unclear. It's theoretically possible but in practicality, a pet that gets H1N1 most likely got it from its owner, who's already exposed the rest of the household members as well.

Vaccination against canine influenza will not provide any protection against H1N1.

More H1N1 cat cases

Perhaps not too surprisingly, more cats have been diagnosed with H1N1. Following the first reported case in Iowa, two more cases have been reported: one in Utah and one in Oregon. The Utah case apparently had typical flu-like disease. The cat from Oregon died of severe respiratory disease.

This doesn't really change anything. We know cats are susceptible, although not highly so considering the small number of cases despite large numbers of cats being exposed by their owners. H1N1 in cats is a human-associated disease, with cats getting infected from infected people. We still have no evidence that pets are a source of human infection. Even so, good general hygiene practices should be used around infected pets and people to reduce the risk of transmission in both directions.

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Stray cats and H1N1 influenza

The topic of the potential for feral (stray) animals, particularly cats, to be sources of human influenza infection came up today. For feral animals to be a public health problem, the following sequence has to happen:

Feral animals need to be exposed to H1N1

  • This is pretty unlikely. Influenza is spread through close contact, mainly through aerosols generated by an infectious person coughing, sneezing or breathing. Influenza only travels short distances in this manner. The likelihood of a feral animal being exposed to the H1N1 influenza virus is very low because it is rare for a feral animal to get that close to people. If there is close contact, it's probably very short term, and not high risk for exposure.

They need to become infected AND shed appreciable levels of virus

  • Considering the number of infected people, how common pet cats are, and the fact that only one cat has been diagnosed with H1N1, the risk of actually transmitting the virus to a cat is very low even with close contact with an infected person. If tens of thousands of household pet cats have had close and prolonged exposure and only one infection has been diagnosed, this virus is pretty poorly transmissible to cats.

They need to be exposed to susceptible people

  • As discussed above, there's not too much contact between stray cats and people. Close and prolonged contact is extremely rare. Influenza is only shed by infected individuals for a short period of time, unlike some other infections. So, the chance of an infected cat having close contact with a person during the relatively short infectious period is very low.

Each one of these events independently is very unlikely. When you combine them, it should be clear that the risks posed by feral cats are extremely low (probably about as close to zero as we get with infectious diseases).

A bigger concern might be someone infecting their indoor/outdoor cat, who would then infect a stray cat, which would then infect another indoor/outdoor cat, which could infect a family member. That's still a VERY unlikely situation - really it's nothing to worry about.

There are certainly public health issues with feral cats. H1N1 is not one of them.

H1N1, cats and the potential for mutation

I've spent a lot of time talking to the press this week about H1N1 and pets. One question that has come up repeatedly involves concern about the potential for this virus to mutate because of its presence in pets. This largely relates to the general knowledge that pigs are potentially important "mixing vessels" for influenza viruses.

H1N1 infection of cats carries almost no risk of a significant mutation. For this to happen, the animal must be infected with two different influenza viruses, and those viruses must recombine so that a new virus containing parts of each of the parent viruses is produced. This virus must then be able to infect a new host and be transmitted. Pigs are a concern because they can be infected by various influenza viruses (from humans and birds, as well as swine-origin viruses), and they tend to live with many other pigs so that the transmission cycle can be started. This isn't the case with cats.

Cats don't have their own influenza virus that is in circulation. Therefore, it's very unlikely that a cat exposed to H1N1 already has a different influenza virus in its system. Even if a cat was infected with a different flu virus (which is exceedingly unlikely) and this virus recombined with H1N1 (which is unlikely even if the two viruses were present), your average cat doesn't have much contact with different individuals, human or animal, and it's quite possible that the virus would just die-out in that animal.

While we don't want to ignore some of the issues regarding H1N1 in pets, such as the potential for pet illness and the unproven possibility that they could transmit H1N1 to other people, we need to keep the concerns in perspective. The risk that pets pose to people is much lower than the already very low risk that people pose to pets, in terms of H1N1 influenza.

H1N1 in a cat

H1N1 influenza has been confirmed in a cat in Iowa. The cat had "influenza-like illness" and was tested, with H1N1 being confirmed today. Two of three people in the house were also sick, but they became ill before the cat, and were presumably the source of infection for the cat. There's no evidence that the cat has infected anyone.

This doesn't really change anything that we've been recommending regarding H1N1 and pets. H1N1 infection is pets is rare but has been diagnosed in ferrets, and now in a cat. Considering the large number of infected people and the presumably large number of exposed pets, the risk of transmission to pets appears to be extremely low. Low doesn't mean no, however, and taking basic precautions is still wise.

Basically, remember that your pets are part of the household - microbiologically as well as socially. If you are doing something to reduce the risk of transmission of infection to people in the household, act the same way around your pets. Reduce contact with pets if you are sick. Avoid being around them when you are coughing. Wash your hands frequently. Avoid contact with their faces. If your pet gets sick after you've had H1N1 (or any other infection) make sure your veterinarian is aware of it.

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Another ferret flu case

A second ferret in the US has been diagnosed with H1N1 influenza. The latest case involves a fatal infection in a ferret from Nebraska that was presumably infected by its owner. Three other ferrets in the household were also sick, and it's fair to assume that they had H1N1as well.

It's important to keep things in perspective. We have two confirmed pet cases among thousands and thousands of human cases. Thousands of pets have presumably been exposed to owners infected with H1N1, with few apparent problems. (You can never rule out additional cases completely, because pets tend to get ignored in outbreak investigations, but there's no indication that this is a major problem.)

This is yet another good reminder of the potential for diseases to move between species in households. If you are sick with a potential infectious disease, you should restrict contact with household members - all household members: human and animal. Ferrets are likely the greatest risk when it comes to H1N1, followed by pigs and pet birds. Dogs and cats are presumably low risk, but we can't say there's absolutely no risk.

If you might have H1N1, reduce close contact with your pets. Don't hide from them, but avoid close face-to-face contact and coughing around them. Wash your hands regularly. More details about household infection control precautions are available from the CDC. Take the same precautions around pets as you would around people. If your pet subsequently gets sick, make sure your veterinarian knows about the possible H1N1 exposure.

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Pets and H1N1 revisited

The recent discovery of H1N1 influenza in a pet ferret has led to another round of concern about the potential impact of H1N1 on pets and pets as a source of human infection. Finding H1N1 in a ferret is not particularly surprising, considering ferrets are susceptible to various (including human) influenza viruses. We shouldn't dismiss the potential that certain pets could become infected by this virus or transmit, it but the overall risks are presumed to be very low. There have obviously been many, many cases of H1N1 influenza in pet owners, yet there is just this one report in a pet (although it's certainly possible that other pets have been infected but not diagnosed). Ferrets may be the biggest concern. Pet birds and pot-bellied pigs may also be at higher risk considering this virus can clearly infect pigs and birds. Cats are probably a bigger concern than dogs because of what we know about cats' susceptibility to (and ability to shed) H5N1 (avian) influenza.

The risks are low to pets and pet owners, but there's rarely a no-risk situation with infectious diseases. A few basic measures should be taken to reduce the risks associated with this pandemic virus:

  • If you have (or think you may have) influenza, treat you pet like other people in your family. Avoid contact with them, especially their faces, and pay close attention to hygiene (especially handwashing). This should help reduce the risk of exposing your pet to H1N1.
  • If you have influenza, or your pet has been exposed to anyone with influenza, and your pet becomes ill (e.g. respiratory disease, fever, lethargy), contact your veterinarian. Avoid close contact with your sick pet (especially the face) and wash your hands after you handle it.
  • Relax and enjoy the company of your pet. The risks of influenza are low.

Swine flu has gone to the birds

Just when all those turkeys that managed to survive Thanksgiving weekend thought their troubles were over, there's new issue: H1N1 influenza (formerly known as swine flu) has been found in an Ontario turkey flock.  The H1N1 virus was first reported in birds in Chile in late August.

This is not a reason to panic.  No one can get the flu from eating a properly-cooked Thanksgiving turkey (nor from any other type of properly-cooked turkey).  The producer has voluntarily (and very responsibly) quarantined the affected flock, and no birds or eggs have left the facility.  There is no risk to the food chain.

Pigs can be infected by human, pig and bird flu viruses, and multiple infections can result in viruses trading genes and producing new viruses that can infect more species.  So it's not too surprising that H1N1can infect people, pigs and now birds as well.  This incident serves as an important reminder that we need to remain diligent about infection control and hygiene, even around animals.  It's highly unlikely that these turkeys had contact with infected pigs - most likely the virus was spread to this flock by a person.  Poultry producers may therefore need to consider getting vaccinated for H1N1 flu not only to protect themselves, but also their flocks, and anyone who may have the flu should definitely stay off these farms.  Hopefully the virus does not become established in wild bird populations (like H5N1 has in some areas), as this would make it much harder to control.

Recommendations for avoiding the flu (H1N1 or other) remain the same:

  • Wash your hands and/or use alcohol-based hand sanitizer
  • Sneeze into your elbow
  • Disinfect commonly touched surfaces
  • Stay home if you are sick
  • Get vaccinated!

Influenza found in Canadian pigs: human source suspected

The new H1N1 influenza virus has been found in pigs in Alberta, Canada.  This marks the first time this virus has been found in pigs, or any other non-human species. It's not surprising - genetically speaking, the virus is most closely related to other swine influenza viruses (which is why it was originally referred to as "swine flu"), so it should be able to infect pigs.  However, this is still a disappointing development because if the virus becomes established in the pig population, the pigs could become a potential reservoir for human infection.

In this case, the source of the pig infections is presumed to be a person - a farmhand that contracted the infection in Mexico. He became ill upon returning to Canada, and the pigs started showing flu-like signs about ten days after he returned to work. Various swine industry and health organizations sent out reminders to pig producers that sick people and/or people returning from Mexico should avoid contact with pigs, however the farmhand in question here returned from Mexico before much of this information became available.

I assume that much more information about this situation will soon become available. A close review of biosecurity practices on this farm is needed to determine if transmission occurred because of defiicient infection control protocols, or whether transmission occurred despite the use of standard practices. The farm is under quarantine and the pigs are being closely monitored to determine what effects this virus will have on them and how long is will stay in the herd. Undoubtedly, close monitoring of other pigs farms (both in Canada and many parts of the world) will continue, with particular emphasis on farms where individuals potentially exposed to the H1N1 virus may have had contact with pigs.

Updated H1N1 (swine) influenza outbreak numbers from WHO

The World Health Organization (WHO) has provided the latest update about H1N1 influenza numbers internationally. (People are still often calling this "swine flu", but it has yet to be found in pigs and is clearly being transmitted human-human now, therefore some have recommended it be called "Mexican flu" or "North American flu" instead.  This also decreases the negative associations with pork products, which are totally unfounded because the virus is NOT a food safety concern). Regardless of the name, this pathogen continues to move across the planet. The WHO is reporting 148 laboratory confirmed cases. Ninety-one have been confirmed in the US with 26 confirmed in Mexico.

It's important to remember that confirmed cases are very much the "tip of the iceberg". It's likely that there are thousands of cases in Mexico, despite only 26 having been confirmed by laboratory testing. For a case to make this list, the sick person has to go to a doctor AND samples have to be collected for testing AND the testing has to be appropriate for identification of swine flu versus other types of influenza. Areas with more diagnostic testing capacity and public health infrastructure (like some places in the US) will end up reporting more cases, even if they actually have fewer sick people. So, we shouldn't become complacent when reading about relatively small numbers of confirmed cases, and we must take care when comparing regional rates.

Confirmed cases have also been reported in Austria (1), Canada (13), Germany (3), Israel (2), New Zealand (3), Spain (4) and the United Kingdom (5). Deaths have only been reported in Mexico and the US, with the single (to date) US death being a child that was visiting from Mexico.

Swine flu: What about the pigs?

We've been talking a lot about the swine flu outbreak the last few days, but so far all we've really talked about are the human aspects.  The reason we're blogging about it on this site is that it's a zoonotic disease - so where do the pigs fit in?

There's a distinct lack of information about where this strain of the influenza virus actually came from.  I heard on the news this morning that one person who was interviewed by a CNN reporter was even trying to blame Canada for the outbreak, claiming that it was Canadian tourists that introduced the disease to Mexico in the first place!  While I'm sure there will eventually be a great deal of investigation into how the outbreak got started (for the moment I think everyone's more worried about trying to just keep it under control), it's quite possible that we'll never find the "index case" or know exactly from where it came.  But one thing's for sure: somewhere along the way, there has to be some pigs involved.

Pigs are the great "mixing pot" of influenza viruses, particularly with regard to avian, human and swine versions of the pathogen.  Pigs can be infected by strains of all these different types, and coinfections (infection with more than one influenza virus at the same time) provide the viruses with a prime opportunity to trade RNA and recombine to form new influenza strains with new properties - more infectious, more virulent, or perhaps better able to infect another species, for example.  In this case we appear to have a swine influenza virus that is not only capable of being spread to people (as occasionally happens with "regular" swine influenza viruses), but also between people, and hence the developing human outbreak.

But what about the pigs?  There isn't a lot of information out there at the moment, with all the focus on the human aspect, but so far Mexican authorities have found no infected pigs in Mexico (at least no where they've looked - so far).   Influenza in pigs is really nothing new, and other swine influenza strains are commonly found in pigs around the world.  Highly pathogenic strains, like those that cause massive devastation of poultry flocks, don't occur in swine.  If an influenza virus gets into a pig barn, however, it's like putting a person with the flu in a crowded room - the virus spreads very quickly through the air over short distances and soon everyone (or every pig) has the flu.  Thankfully the virus generally also moves on quite quickly, and after a few days the animals generally start to recover.  While such an outbreak certainly affects their growth efficiency, very few (if any) pigs die.

Yesterday the Canadian Veterinary Medical Association (CVMA) distributed a fact sheet on swine flu from the Canadian Food Inspection Agency (CFIA) for all Canadian veterinarians and swine producers.  The CFIA is encouraging increased vigilance with regard to monitoring and diagnosing disease in Canadian pigs, to prevent the disease from spreading through the swine population.  In addition to emphasizing vaccination, good hygiene practices and biosecurity, particularly around sick pigs, they also point out that it's equally important (especially now) for anyone who may have the flu to avoid contact with pigs (be they Canadian pigs or pigs in any other country), in order to avoid spreading the virus to them.  Hopefully people in other countries will take the same precautions.

Another very important point is that swine influenza is NOT a food safety concern.  The virus does not survive well in the environment for very long, and therefore cannot survive on pork products, and certainly cannot survive proper cooking (which is always very important for any kind of meat).  The fact that some countries are banning pork imports is really not going to do anything to help control the outbreak - the concern should only be about live pigs (and people).  So you can still have pork sausages at your next spring barbeque, just ask anyone who's feeling "under the weather" (or a little flu-ish) to please stay home!!

Interactive swine flu map

GoogleMaps has an interactive swine flu map that is quite interesting. The map indicates where cases of the disease have been diagnosed or are suspected, and it's updated frequently.  Clicking on a marker gives you more information about what is happening in that particular location. Many of the pink "suspected" markers will probably turn out to be negative, but I fear the map's going to get a lot more crowded over the next couple of days. The picture below is a captured image of the map, but click here for the live interactive version.

Pets and household quarantine

A few years ago, I wrote a commentary in the journal Emerging Infectious Diseases about pets and household quarantine. It was written after SARS (severe acute respiratory syndrome) had caused tremendous problems in many areas, including Toronto. The point I was trying get across was that while there was a strict household quarantine implemented for exposed people, there was no consideration of pets. We now know that cats can become infected with the SARS coronavirus, and can transmit it to other cats. However, when people were quarantined, there were no recommendations for pets - pets could interact with quarantined people, then visit non-quarantined family members, or interact with other animals or people outside. From my standpoint, this was a significant concern.  If cats had become infected with SARS, they could have been a source of transmission in households and potentially beyond. If SARS had infected the feral cat population in Toronto, it might have been very difficult to eliminate. I encouraged groups to ensure that pets are included in household quarantine guidelines.

The topic is front and centre again with swine flu. We don't know whether dogs and cats can be infected with this particular swine flu virus, but we DO know that cats can become infected with H5N1 avian flu and shed the virus. In my mind, that means that we should consider pets susceptible until proven otherwise.

So what should we do if people are being quarantined?

  • If you are quarantining the family, quarantine the WHOLE family, including pets.
  • Quarantined cats must be kept in the house. Quarantined dogs must be kept in the house as much as possible. They should only be taken outside to urinate/defecate, and this should be in a "remote" area where they can't have contact with other people or animals. They should always be under physical control (e.g. on a leash) when outside.
  • If a quarantined pet gets sick, a veterinarian should be called first. That way, it can be determined if the pet needs to be examined, and if so, the clinic can know when it's coming and have protocols set up to handle it with infection control precautions.

EU recommends avoiding US/Mexico travel

The European Union's Health Commissioner has recommended that Europeans avoid all non-essential travel to the US and Mexico (Canada's apparently under the radar so far) as a measure to contain the spread of the emerging swine influenza virus. This has been met with some disdain by US officials, who emphasize the small number of cases (so far) in the US, and the much, much larger numbers of people that die in various countries every year from classical human influenza.

It's hard to say what type of restrictions are appropriate at this point in the outbreak. In general, it's better to be prudent and excessive (within limits) when dealing with a developing problem. The lack of information about the true scope of the problem, and the delays from transmission to definitive diagnosis of new cases, complicate assessments about whether the problem is truly contained, or containable.

Swine flu was most recently confirmed in Spain, and it has probably reached many different countries. It is also suspected in a group of students in New Zealand that recently visited Mexico.  Considering the massive volume of travel between North America and much of the world, and the wide geographic range of cases in North America, it's hard to envision keeping this localized.

The fact that this outbreak is going to be difficult to contain, however, should not be taken as an excuse to not try to contain it. Even if this virus spreads to many different countries, good infection control and surveillance measures can help limit the impact of the disease.

Photo: Chichen Itza, one of the major tourist attractions on the Yucutan Peninsula in Mexico (credit M. Anderson)

Swine flu confirmed in Canada

Not surprisingly, swine influenza has been confirmed in Canada: 4 cases in Nova Scotia and 2 cases in British Columbia. More cases are certain to follow. As in the cases reported from the US so far, all Canadian cases have been mild.

The 4 cases from Nova Scotia were from the same high school. One of the affected students had been on a school trip to the Yucatan Peninsula in Mexico recently. Presumably, he or she picked up swine flu in Mexico and other students were infected by that student or others that went on the field trip. This is similar to a cluster of cases from a high school in New York. Eight students from that school were diagnosed with swine flu while more than 100 students had flu-like disease (it's unclear how many of these were tested).  The two cases from BC were both in people who recently returned from Mexico themselves.

I imagine that we're going to see almost hourly reports over the next few days describing swine flu cases in people in various regions. Lets hope the pattern of mild disease that has characterized the Canadian and US cases persists.

US government declares public health emergency over swine flu

In response to increasing numbers of confirmed or suspected cases of swine flu in the US, plus a still relatively unknown number of cases and at least 81 deaths in Mexico, the US government has declared a public health emergency.

This H1N1 swine influenza virus has many of the hallmarks of a virus with pandemic potential. It is of animal origin but has a unique combination of gene sequences that has not been found previously in swine or human influenza strains. People don't have pre-existing antibodies because they have not been exposed to it before, which leads to the chance for widespread disease. A big concern is that it seems to spread at least somewhat efficiently between people (unlike the H5N1 avian flu virus which is not efficiently transmitted between people). Fortunately, while it can cause death, this swine flu virus does not seem to be as deadly as avian flu, which kills approximately 50% of the people it infects. Therefore, while swine flu appears to be much more transmissible, it's probably not as fatal. (However, the large number of reported deaths in Mexico and early stage of the outbreak at this point means we need to be cautious making such statements).

It is clear that this swine flu strain is spreading in the US. It's been found in multiple US states and it is probably going to be found throughout the country.  Mild cases have already been confirmed in Canada, and there are suspected cases in other countries. The number of cases in different regions and the amount of international travel makes containment of a reasonably-transmissible virus very difficult.

Some tips to reduce the risk of catching (or spreading) swine flu:

  • Wash your hands regularly, particularly after contact with other people or common-contact sites (e.g. public door handles, public transit).
  • If you are sick, STAY AT HOME. The era of "sucking it up" and going to work when you are sick should be over. All you're doing is putting others at risk.

More information about swine influenza can be found on the CDC's swine influenza website.

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