ProMED-mail, 2004h) and domestic cats (Kuiken et al., 2004) through the ingestion of raw chicken. The Thailand Zoo tiger outbreak killed more than 140 tigers, causing health officials to make the decision to cull all the sick tigers in an effort to stop the zoo from becoming a reservoir for H5N1 influenza (ProMED-mail, 2004i; ProMED-mail, 2004w). A study of domestic cats showed H5N1 virus infection by ingestion of infected poultry and also by contact with other infected cats (Kuiken et al., 2004).
Throughout Asia, affected countries responded to the avian flu epidemic with time-tested strategies: surveillance to detect the outbreak and monitor the progress of control efforts; culling potentially infected birds; disinfection of affected facilities, including the safe disposal of dead and culled birds; and educating poultry farmers and the general public about the threat posed by H5N1 avian influenza. Yet each country’s circumstances and their handling of the epidemic were unique, as illustrated by workshop presentations by agricultural and public health officials from Indonesia, Vietnam, and Thailand. The diversity of these responses, and their resulting outcomes, offer important lessons for the control of future avian flu outbreaks—a key protection against a human pandemic.
Although Indonesia was one of the first Asian countries to experience cases of H5N1, which was identified in Central Java in August 2003, a comprehensive control strategy was not initiated until November (Soebandrio, 2004). By that time, the disease had spread throughout Java and had also been detected on the islands of Bali, Sumatra, and Borneo. This late start, along with the fact that the epidemic had spread widely and affected many small farms, made disease control a daunting challenge. Nevertheless, a strong effort was made to cull all domestic birds on all farms and facilities where H5N1 was detected. Surveillance for human infection was also conducted among more than 1,000 people (80 percent of whom had direct contact with poultry; the others as controls) in affected provinces; no positive cases were found by Reverse Transcriptase (RT)-PCR.
Unlike most other affected countries, Indonesia also instituted mass vaccination of healthy domestic birds against H5N1, followed by routine vaccination (China has a similar policy; other Asian countries are considering it [ProMED-mail, 2004j]) (Soebandrio, 2004). This is a risky strategy, because vaccinated birds can develop asymptomatic infections that allow virus to spread, mutate, and recombine (ProMED-mail, 2004j). Intensive surveillance is required to detect these “silent epidemics” in time to curtail them. In Mexico, for example, mass vaccination of chickens against epidemic H5N2 influenza in 1995 has had to continue in order to control a persistent and evolving virus (Lee et al., 2004). The prospects, advantages,