Wednesday, April 29, 2009

Swine Flu Update

Since I wrote the post on flu pathophysiology, there have been several developments in the 2009 swine flu story.  First of all, it is still likely that no one who caught this virus within the United States, has died.  The report about the 23 month old toddler concerns a young boy who came to a border town of Brownsville, Texas from Mexico City.  Several news stories describe him arriving on April 4th with health problems.  His symptoms became typical of flu by April 8th, and after being very ill for several weeks, he developed bacterial pneumonia.  In a very sad turn of events, he eventually died.  

The reason why I make a big deal about where this boy was exposed to this flu virus, is because it would be inaccurate to claim that this boy is representative of the people now being diagnosed with the swine flu virus within the United States.  There was recently a large number of children in Queens, NY who have also been diagnosed with this flu virus strain.  This occurred at a very large private school, which is attended by 2700 students.  Approximately 140 children became ill, but they have all experienced only mild symptoms. Some of these children were contacted, and viral cultures could be obtained from their nasal secretions.  Of those tested, nearly all turned out to be positive for the unusual swine flu strain - the same one that was earlier reported in Mexico.  If the other children were reachable and consequently testable, the number of confirmed cases in NYC would have been much larger.  One very important aspect of this outbreak that is worth restating, is that all these NYC children had only mild symptoms.   In Mexico, some people are claiming that this infection carries a 7% risk of being lethal, while among the American population thus far, the mortality is 0%.

As we are trying to obtain an accurate number of Americans who contracted this flu virus, there are strange guidelines now being advocated for testing patients.  These guidelines specify that only those who have severe respiratory symptoms or a very high fever, should undergo the collection of samples to be tested for viral typing.  What is so strange about such instructions, is that from the newspaper descriptions of the NYC swine flu sufferers,  none of the recently confirmed cases would have been approved for viral testing.  In other words, if these guidelines were followed, then there would likely be no confirmed cases in NYC.  There are several bogus reasons being given for instituting such policy, including the idea that the CDC office might get overwhelmed with samples.  It may actually be that there is some dumb bureaucrat trying to conserve the "valuable" supply of nasal swabs.  I find it very hard to believe that everyone associated with drafting policy is that lightheaded, so some must have other reasons.  Despite thoughtlessness, the only reason to promote such nonsense, while knowing it would miss most of the people coming down with this illness, is to pretend that this problem has not really affected New York City.  Why?  Because a large outbreak would cut down on travel and the flow of tourist money. This really reminds me of a scene from the movie Jaws.   Could a similar policy have affected the Mexican reporting of this outbreak?

Returning to Mexico, it would seem highly probable that the number of people sick with this flu has been grossly under-reported.  If the parents of the boy described above, fled to the US on April 4th, there must have been a significant outbreak there prior to that date.  I would guess that people have been becoming ill with this particular virus for at least several months. Considering the number of sick tourists returning from Mexico, I would also have to conclude that a significant portion of the Mexican population has been exposed to this flu strain.  Not just some 2000 people reported in newspapers, but likely hundreds of thousands, or more.  If that is the case, it would make a lot of sense to not bring your family to Mexico on vacation at this time.

Furthermore, If I am correct about a widespread epidemic with this flu virus occurring in Mexico, the relatively low number of deaths reported would correlate with the American experience.  Within the United States, the yearly flu affects approximately 10% of the population which translates to roughly 30 million sick Americans each year.  If 36,000 die of flu related causes each year in this country, it would suggest a mortality of 0.1%.  We shall soon see if this particular strain is any more deadly.  

Another explanation for the reported number of people affected by the swine flu and the strangely large number of corresponding deaths in Mexico, is that the virus affecting people in Mexico City may have been more lethal than the virus that was spread to tourists returning from Mexico.  The usual swine flu virus affects a small number of people in the US each year, and it is not easy for a human to become infected with it. Typically it only occurs in situations where someone has a significant exposure to swine, like working at a pig farm.   Those people who develop an infection, can have severe symptoms.  It is possible that this flu strain has affected a large number of swine in Mexico, and consequently spread to a limited number of people in that area.  Within the human host, the virus might have mutated and became more easily transmitted among humans.  This may have led to a slightly different virus that was transmitted to a student from the NYC school and then spread among others at that school.  This scenario could also account for the very different reported experience among Mexicans and Americans, who came down with the swine flu.  It should also be reassuring that if you developed flu symoptoms and have not recently travelled to Mexico or spent much time among pigs, you shouldn't expect more of a problem than you would get from any other flu.

At this time, all of the predictions for the impact of this swine flu outbreak are suspect, because we simply don't have an accurate assessment of the situation in Mexico.   They have not tested a a large enough sample of the population, for the presence of this virus.  I believe that political and economic considerations have skewed the data, and we simply don't know how many are sick and how many deaths are related to this swine flu strain.  Of those reported deaths, we don't really know what they died from.

In summary, there is still no real indication that this swine flu virus is any worse than the other flu virii we have encountered recently.  If you develop symptoms, you should drink plenty of fluids and rest.  Your co-workers would greatly appreciate not being coughed on, and you may not even need to present a doctor's note these days.  If you are very young, very old, or have significant other health issues, you should see your doctor and be evaluated for treatment with the available antiviral therapy.   If your symptoms improve and then suddenly worsen, you should definitely seek a doctor as you may need antibiotics.

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