Wednesday, 27 May 2009

The politics of flu

There's nothing like having your holidays ruined to make a person angry and start looking for someone to blame. Hence the elevation of swine flu back into pride of place in the Australian media today. After a couple of weeks out of the headlines this new virus is well and truly back in the headlines with an outbreak on a cruise ship setting off some interstate bickering between health department officials. That is the kind of thing that Federal Health Minister Nicola Roxon hopes does not spread because the horrors of coordinating anything under a federal system of government will not stop the mob blaming her if and when things go wrong
Thankfully this A(H1N1) version of swine flu has not yet emerged as an extraordinarily virulent killer. As Australia's chief medical officer Jim Bishop.reported this morning it is essentially a "mild disease" that was responding well to antiviral drug Tamiflu. Professor Bishop told ABC Radio that modelling on a normal influenza season predicted about 10 per cent of the national population could be affected, though it was hoped measures already in place would significantly reduce that possible toll.
That just might be a little optimistic. The World Health Organisation in its latest notes on Assessing the severity of an influenza pandemic says H1N1 appears to be more contagious than seasonal influenza. The secondary attack rate of seasonal influenza ranges from 5% to 15%. Current estimates of the secondary attack rate of H1N1 range from 22% to 33%. The good news from the WHO is that with the exception of the outbreak in Mexico, which is still not fully understood, the H1N1 virus tends to cause very mild illness in otherwise healthy people. Outside Mexico, nearly all cases of illness, and all deaths, have been detected in people with underlying chronic conditions.

The WHO says that in these early days of the outbreaks, some scientists speculate that the full clinical spectrum of disease caused by H1N1 will not become apparent until the virus is more widespread. This, too, could alter the current disease picture, which is overwhelmingly mild outside Mexico.

Apart from the intrinsic mutability of influenza viruses, other factors could alter the severity of current disease patterns, though in completely unknowable ways, if the virus continues to spread. The scientists are concerned about possible changes that could take place as the virus spreads to the southern hemisphere and encounters currently circulating human viruses as the normal influenza season in that hemisphere begins.

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