Domesticated poultry should not be raised inter-mingled with pigs which are susceptible to be infected by both poultry flu viruses and human viruses. There are eight different fragments of nucleic acid inside a flu virus. When two different viruses infect a cell simultaneously, there is a possibility of recombination and rearrangement among their constituent nucleic acid fragments. This could result in a completely new virus which might bring about a deadly pandemic bringing a worldwide disaster down upon the human population.
In addition, chickens should not be reared together with waterfowl like ducks and geese. This is because the incidence of various subtypes of the flu viruses among waterfowl tends to be rather high even though the affected waterfowl may not be showing any clinical symptoms. Viruses in the waterfowl feces would be likely to find their way into the chickens resulting in an outbreak of bird flu and severe economic damage.
(China.org.cn February 13, 2004)