No one knows for sure. Influenza viruses are highly unstable and their behaviour defies prediction. However, WHO remains optimistic that, if the right actions are taken quickly, an influenza pandemic can be averted. This is WHO's foremost objective at present.
The first priority, and the major line of defence, is to reduce opportunities for human exposure to the largest reservoir of the virus: infected poultry. This is achieved through the rapid detection of poultry outbreaks and the emergency introduction of control measures, including the destruction all infected or exposed poultry stock, and the proper disposal of carcasses.
All available evidence points to an increased risk of transmission to humans when outbreaks of highly pathogenic avian H5N1 influenza are widespread in poultry. As the number of human infections grows, the risk increases that a new virus subtype could emerge, triggering an influenza pandemic. This link between widespread infection in poultry and increased risk of human infection is being demonstrated right now in Asia. All human cases and deaths detected so far are in two countries - Viet Nam and Thailand - with very widespread outbreaks in poultry.
WHO stresses the urgency of the situation and the need for rapid action in the animal and agricultural sectors. For example, the culling in 1997 of Hong Kong's entire bird population - an estimated 1.5 million chickens and other birds - was done in 3 days. Again in 2003, the culling of nearly 30 million birds (out of a total bird population of 100 million) in the Netherlands was done within a week. Rapid action in both of these situations is thought by many influenza experts to have averted an influenza pandemic in humans
