Where did it come from?

I've been reading a fair number of blogs on swine flu lately, and I keep coming across claims in the comments that we should stop calling it swine flu because it has nothing to do with pigs.

What utter porkies!

Researchers from the UK, Hong Kong & and the US have reconstructed how and when this strain of the virus developed. By comparing the genome sequences of the pandemic strain with 100s of other strains from pigs, birds and humans that represent the full spectrum of influenza A viruses, the team was able to build a family tree of swine flu and date when it appeared.

And it quite definitely came to us via pigs - take a pig-shaped bowl, add a couple of dashes of avian flu, a dollop of human flu, and a splash of swine, and mix it all around for about 20 years, and then let it marinade for another 10 years before pouring it into a human-shaped vessel - ready for serving in January.

Yep, January, not April. This strain of swine flu made the leap to human hosts in January of this year - which means that it had quite busily circulating amongst the Mexican population like flu usually does for several months. And like flu usually does, it killed a number of people (NZ loses about 100 to seasonal flu every year). Those people were tested to see what they died of and the new strain of flu was revealed to be the culprit.

Tada! A new, apparently quite deadly, strain of flu erupts into the world view. Except that the numbers are a bit skewed as the first cases of swine flu to be confirmed are deaths. If nine out of the ten cases you've found are dead because of it, then it appears to be very deadly indeed, but when you test more and more people, and find that most people who've caught it just thought they had a bad cold and didn't bother going to a doctor, then the situation changes. I wouldn't be surprised to find that a quarter of Mexico had caught it and gotten over it already by the time it "emerged".

And now it's here, and running wild and free throughout the population. We've given up containing it in most places and we've stopped testing for it except in extreme cases, and keeping the Tamiflu for those extreme cases or people who are high risk because of other health issues. It's now effectively part of the seasonal flu collection - though interesting to note that the 18 other strains of influenza A doing the rounds this season are all Tamiflu-resistant.

Just because we've stopped testing for it and isolating people who might have it doesn't mean you can go back to going to work sick anymore - if you come down with the flu (any kind of flu) you should follow all the same procedures - stay home until you have been clear of symptoms for 24 hours, don't spread your germs around.