If mainland investigators are missing the virus, it may be because efforts to block it are inadvertently hiding it. China developed an avian influenza vaccine for poultry in 2005 and inoculates millions of birds annually. But not everyone agrees it’s a panacea. In 2005 Dr Robert Webster, a influenza expert at St Jude’s Children’s Hospital in Memphis, Tennessee, suggested that China may have been using substandard vaccines that stopped symptoms of bird flu in poultry but allowed the virus to continue to spread. Recently, Guangzhou-based expert Zhong Nanshan has also said there is a danger that China’s widespread vaccinations could conceal the virus. “Special attention should be paid to such animals, including those that have been vaccinated,” Xinhua news service quoted him as saying on Feb. 6. “The existing vaccines can only reduce the amount of virus, rather than totally inactivating it.”
Mainland controls may also be lacking another layer of more basic prevention in the way that live chicken markets, prevalent throughout Asia, are inspected. Some worry that Chinese monitors may only be calling for culls once a large number of poultry has become sick, as in the Hotan case this week in which 519 birds died. In contrast, last year Hong Kong culled thousands of birds after a regular inspection found only infected chickens in a wet market. The infected birds, experts say, showed no external signs of disease, and could have been missed if inspectors were only screening birds that were dead or visibly ill.
Also on the TIME website is a photo essay that documents the global impact of the bird flu crisis.