The incubation period for bird flu normally ranges from a few hours to several days and may extend up to a maximum of 21 days. The actual time taken for incubation depends on a number of factors such as the toxicity and concentration of the virus, the bird's level of resistance, age, size, species, poultry-rearing methods, nutrition, environmental cleanliness and irritability factors. HPAI has a short incubation period. Affected birds will normally become very ill and suffer from high morbidity and mortality.

There is likelihood of the bird being infectious during the incubation period.

(China.org.cn February 13, 2004)