H5N1 avian influenza is an infectious disease of birds that can be spread to people, but is difficult to transmit from person to person. Almost all people with H5N1 infection have had close contact with infected birds or H5N1-contaminated environments. When people do become infected, the mortality rate is about 60%.
Public health scientists want to know if genetic changes in the virus could make it more easily transmissible between people, so they can improve public health surveillance for early detection of potential pandemic strains. Researchers have recently succeeded in creating H5N1 viruses that are more transmissible in mammals than those that occur naturally, raising concerns about the risks and safety of such research.