Bird flu outbreak started a year ago

From The News Scientist

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In the past week, country after country has admitted that millions of birds and a few people have succumbed to bird flu, and it has become clear that we are facing the worst ever outbreak of the disease.


So how have things got so out of control? After strenuous denials, Indonesia has admitted the H5N1 virus has been spreading there since August. Thailand admits it had it in November. China says the disease was first detected this week.



In fact, the outbreak began as early as the first half of 2003, probably in China, health experts have told New Scientist. A combination of official cover-up and questionable farming practices allowed it to turn into the epidemic now under way.



Asia's growing prosperity has been accompanied by a boom in intensive poultry production. After 1997, when all the chickens in Hong Kong were destroyed after H5N1 bird flu killed six people, Chinese producers decided to take no chances, and started vaccinating birds with inactivated H5N1 virus.



This may have been a mistake. If the vaccine is not a good match for the virus - as is the case with the H5N1 strain now sweeping Asia - it can still replicate but most animals do not show signs of disease.

In this way, the intensive vaccination schemes in south China may have allowed the virus to spread widely without being spotted.



'We don't like vaccination,' says Hans Wagner of the UN Food and Agriculture Organization in Bangkok.


This is also why the World Health Organization has reacted with dismay to Indonesia's announcement that it will tackle its outbreak with vaccination instead of culling.

Vaccination may even have contributed to the origin of the latest variant of H5N1, as it would put strains that could evade the vaccine at an advantage.



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