All entries for Friday 07 April 2006

April 07, 2006

Why H5N1 isn't to be taken so lightly

DON'T PANIC (A la Hitch hiker's guide)

I've noted a lot of people over the past couple of days talking on blogs about avian influenza and the spread of the H5N1 virus around the globe, now confirmed also in the UK. Most people seem to be rubbishing the media coverage as being panic inducing, pointing to the facts that H5N1 and other strains of avian influenza are only spread to humans in rare cases, and even then only with direct contact with infected or dead birds. While there's some truth to this, it doesn't paint the whole story.

If you do a little background reading on avian influenza then you quickly learn an awful lot more than you do from the media coverage. Check out Wikipedia's section on it and also the Department of Health information page on avian influenza. There are a number of facts that stand out to me here, which make it very different from previous health scares such as BSE and SARS, which I believe have made us immune to media coverage in a manner analogous to the story of the boy who cried wolf:

  • The current variation of H5N1 is highly pathogenic, and rapidly spreading across the globe

  • Like all viruses, it mutates with ease. We know what factors make a flu virus a human virus (easily passed from one human to another human), and from this knowledge we know that H5N1 is the biggest pandemic threat of all stains of influenza in circulation. It is just one antigenic shift mutation or a couple of antigenic drift mutations from being an avian influenza virus to a human influenza virus

  • The difference between an epidemic (such as the regular outbreaks of influenza we have yearly) and a pandemic is that a pandemic threatens a global population, compared to an epidemic which is concentrated on one population

  • In order for a flu pandemic to occur from H5N1, it must first mutate into a form in which it can transmit easily between humans. This rapidly will then turn into an epidemic if not caught, and then from an epidemic it will become a pandemic. Experts widely believe that it will not be possible to prevent any of these stages from happening with H5N1

  • Pandemics have the capability to kill millions, if not hundreds of millions of people. The current worst case projection for H5N1 is somewhere around 150 million

  • This has happened before. In 1918 and 1919, an avian influenza became pathogenic and killed between 50 and 100 million people worldwide (called "Spanish flu"). And compared to today, world travel was minimal.

  • There are serious technical problems with combatting a pandemic with vaccines. Once the virus it identified, the development takes several months. H5 appears to require relatively large doses of vaccine to be effective. A large trial found two injections at 6 times the strength of a seasonal flu jab (which you only get once a year, if you have one) gave protection in only 54% of a population. Currently, the world has the capability to produce around 900 million does at a strength for the seasonal flu jab; therefore we would need at least 12 times this production capacity just to immunise less than a sixth of the world population with 54% success rate. Furthermore, there are two different clades (like branches) of virus in circulation. Research is focused on clade 1 viruses; the clade 2 virus is antigenically distinct and a clade 1 vaccine will be unlikely to offer protection against a clade 2 virus pandemic

  • About the only bit of positive news on H5N1 is that it currently hasn't mutated into a human virus, so as yet we have little to fear from it. Most experts believe it's not a matter of if but when this happens though. There's no need to panic right this instant, but taking it seriously would be wise

I would like at this point to explain why I'm making these points. Firstly, I'd like to educate people beyond the media hype; I believe the readership here has more than enough brains to grasp more than the basic facts you can hear on the 10 o'clock news. Secondly, I want to make it clear to people that it's not a case of the authorities crying wolf, there is a very real danger here for a huge virus outbreak. I don't however write this with the view of initiating mass panic. Rather, I think it's important to approach the facts with a level head and accept the reality of a possible outbreak, but when that outbreak happens (it could be tomorrow, it could be in a year, it could never happen) we have prepared ourselves for it, that we don't panic, and that we have well thought out contingency plans to put into place.

Awaiting corrections on the technicalities from Craig and other biochemists/geneticists etc.

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