The exchange of genetic material between two closely related strains of the influenza A virus may have caused the 1947 and 1951 human flu epidemics, according to biologists. The findings could help explain why some strains cause major pandemics and others lead to seasonal epidemics.

Recent findings from study of incentives, decision-making, and influenza epidemics may offer guidance on public health policy.

Regular as clockwork, the flu arrives every year.

Regular as clockwork, the flu arrives every year. And, according to the national Centers for Disease Control and Prevention, 5 to 20 percent of the U.S. population on average will come down with it. About 36,000 people will die.