The transmission of HPAI among poultry flocks mainly depends on such modes as air, droppings, feedstuffs, drinking water, etc. Current evidence indicates that HPAI is not transmitted via eggs. Nevertheless, experiments have demonstrated that the eggs of infected chickens do contain the influenza virus. The possibility of vertical transmission to offspring therefore cannot be ruled out totally. The declining rate of fertilization and incubation in the affected chickens meant that these eggs could not be hatched.
(China.org.cn February 13, 2004)