Given that the longest incubation period for HPAI would be 21 days, there would be every likelihood of the emergence of a new case of bird flu during that time. Only after the expiry of one full incubation period or longer, with no new case of infection reported, can freedom from the viral infection be confirmed. Once the blockade has been lifted the area will be assumed to be free from epidemic. Therefore a blockade of the HPAI-hit area can only be lifted after at least one incubation period has past following the culling of the last of the poultry.

(China.org.cn February 13, 2004)