Swine Flu.  Horrors!  Why it seems like only yesterday the fear was Avian Flu.  That was yesterday's horror.

Just so you will know, for seven years I isolated and subtyped influenza virus as part of my duties as a clinical virologist for the State Public Health Laboratory of Arizona.  We were the reference laboratory for the state from all of the other clinical laboratories, who sent us a representative sampling of their isolates.  A lot of isolates. 

Most people don't really realize it but influenza or (aka) flu kills an estimated 36,000 people a year in the USA.  The vast majority are either under 5 years of age or over 55 years old.  Cause of death is almost always pneumonia.

The current swine flu's mortality rate of 7% is not much higher that any other flu we have recently experienced.  So why the media generated scare?  Ahhhh, that is a good question.  Yes it is unusual to get flu this late in the year.

Flu season in the USA typically cranks up in late Sept-early October and ends by the middle of March --- as it did this year.  Then a bunch of so called H1N1 associated with "swine" flu were detected in April.  Almost all had strong Southern Mexico association. 

The southern part of Mexico, Central and South America have a flu season that extends a few more weeks.  While it should now be over, it is less surprising that this flu outbreak is occurring now in Mexico City.  The cases in the USA have almost all been easily connected with a recent visit to Mexico.

Mexico City has some of the worst air pollution in the world leading to increased pulmonary complications and increased infectivity from compromised lungs and increased death from the stress of oxygen deprivation.  Undoubtedly this contributed to the late blossoming of this new strain of influenza virus, and to a somewhat higher than normal rate of death.  But as you have seen, in the USA there has only been one death --- a 23 month old child from Mexico City transported to a Houston hospital in an unsuccessful attempt to save its life.

Typical flu cycle:  Influenza viral strains appear in the Asia's and are associated with livestock, particularly pigs (swine).  They migrate north into Europe.  From here the virus hops a flight on migratory birds landing in the North Americas.  Eventually migrating south for the winter in the Central and South Americas. 

Avian and Swine transmission is common, and usually certain genes (the virus has eight genes in its RNA chromosomes) will mutate to adapt to its transmission through a common set of hosts.  Influenza virus has a high mutation rate.  Additionally it has 8 unique chromosomes (each with a single gene) that can reassort if two or more unique strains are present infecting the same cells in a host.  This is where the terms avian and swine influenza are from. 

Human to human transmission is the predominant way flu is spread in humans.  Human to human transmission f0r this particular swine flu strain do not seem to be good.  Only one case has good evidence for such transmission.  Too warm and dry for flu to thrive in our country right now.  Hence my lack of credence at the panic and steps being taken by various governments around the globe.   This is no worse than any other flu.  So why the attention and excessive government preparation?

Masks?  DO they work?  Yes, despite what our  government says, masks help.   But they are correct, masks only help if you walk into a room occupied or recently occupied by someone  infected with the flu where droplets of infected material expelled from the mouth (lungs) may still be circulating in the air. That doesn't last too long.  Most transmission of the virus occurs when we touch a contaminated surface and rub our face and eyes.  Something we subconsciously do many times a day.  Here is where the claims of hand cleaner to cut down on transmission come it.  Such alcohol based solutions are quite effective in removing any influenza contaminated material from hands, and any soap is equally effective.  The influenza virus is quite readily killed by either.

The government has advocated masks on infected people.  I really do not like that suggestion.  While it would be very effective in keeping the virus from being transmitted to others, IF a sick person is showing ANY respiratory distress at all they SHOULD NOT be wearing a mask that will add to their difficulty of breathing.  This can contribute to respiratory and circulatory failure.

If you do buy masks look for ones labels N-95 or higher.  This means it will block 95% of all particles 0.3 microns or larger.  Be sure the mask securely seals against the face completely around the mask.   Any break, including caused by facial hair, will be where the air is drawn in and not through the filter of the mask --- defeating the mask.  Psychologically some people do not like wearing a mask or need some hours of on and off wear to acclimate.

My bottom line, this whole flu thing is blown way out of proportion.  It is unlikely to be of threat to the USA, is unlikely to last long and current government preparations are not about the flu.  I will not be wearing a mask or doing anything I would not normally do --- indeed I went grocery shopping this morning.

Addendum-- The swine flu isolate is interesting in that it has around a 6% difference in genetic sequence compared to this years H1 isolates.  This is huge!  There does not seem to be a link between this strain and any in circulation around the globe this year.  Nor does it match any in circulation that have been preserved and sequenced.  It bears some similarity in appearance, but not sequence to a 1998 H3 strain that circulated in pigs.  The interpretation is this isolate was in circulation elsewhere in the world undetected and then was transported to Mexico City in late March where it exploded in an dwindling flu season.