Influenza pandemics

As a result of reassortment, new influenza virus subtypes are formed. This happens, very roughly, about every twenty five years and will happen again. It  could have occurred in 1997 had not the Hong Kong authorities rapidly killed off the entire poultry population. In order to  lessen the possibility of a new pandemic it is vital that infected chickens be destroyed to stop the spread to other birds. Workers in the poultry industry need to be protected from infection by avian flu using a vaccine and prophylactic chemotherapy. Many of these workers will get human flu and it is very important that they not be simultaneously infected with avian flu.

From CDC and WHO