Tracking the source of avian flu

On a trip to Hong Kong eight years ago (2003) I tried to book a visit to the Mai Po nature reserve in the New Territories. But I was told that it was temporarily closed to protect visitors from the risk of infection with the H5N1 strain of avian influenza.

How crazy, I thought. Surely the last place you are likely to catch bird flu is in a remote coastal wetland area where you only have distant views of the birds across acres of marshland and tidal mud. The real risk in the Far East surely lies in the congested cities, with pigeons and sparrows feeding round your feet and crowded markets selling live chickens and ducks.

I later learnt that the World Wide Fund for Nature, which manages Mai Po, shares my view. In 2006, during one of several further enforced closures of the reserve, the WWF pointed out that there was not a scrap of scientific evidence that people could contract avian flu from wild birds.

Furthermore, since the first outbreaks of H5N1 bird flu in 2003, it had tested more than 16,000 wild birds at Mai Po and none had proved positive for the virus. It also criticised the Hong Kong authorities for having harsh rules for Mai Po but lax standards in urban areas.

The need for stricter measures in cities has now been backed by researchers based in London, who have developed a model showing how live bird markets act as a reservoir of infection in domestic poultry.

Writing in Interface, the journal of the Royal Society, the researchers advocate introducing frequent rest days during which bird markets are emptied and disinfected.

This action, their model predicts, would be almost as effective as closing the markets altogether and at least as effective as farm interventions such as slaughter or vaccination. And, of course, it would be infinitely more useful than pointlessly closing remote nature reserves.   

Oh, by the way, the researchers’ model was actually based on the live bird market chain in Hong Kong. Let us hope that all countries still affected by avian flu quickly adopt the researchers’ recommendation.