How might human health be affected?
A widespread persistence of H5N1 in poultry populations poses two main risks for human health: (1) direct infection when the virus passes from poultry to humans with resultant severe illness and (2) a greater concern is that the virus will change into a form that is highly contagious among humans and begin to spread easily from person to person, starting a global outbreak (pandemic). Of the few avian flu viruses that have crossed the species barrier to infect humans, H5N1 has caused the most severe disease and largest number of deaths. Unlike the seasonal human influenza which causes only mild respiratory symptoms in most persons, influenza caused by the H5N1 virus usually follows a very aggressive clinical course with a high mortality rate (approximately 50%). Death is usually from viral pneumonia and multi-organ failure and occurs most commonly in previously healthy children and young adults.
