How does avian influenza spread from birds to people?

There have been nine reported cases of transmission of avian influenza virus from infected birds to people over the past 50 years. In cases caused by the H7 strain, infected people developed conjunctivitis while H5 cases experienced respiratory illness and flu-like symptoms. To date, the largest AI outbreak involving bird to human transmission is the one caused by the highly pathogenic avian influenza (HPAI) H5N1 strain. This outbreak started in Hong Kong in 1997 with 18 human cases and 6 deaths but subsided. It resurfaced in 2003 and has affected more than 440 people (262 of whom have died) in 15 countries in Asia, Africa, and the Middle East as of August 31, 2009. Most of these cases have been linked to direct exposure to live or dead poultry infected with HPAI H5N1. These human infections have occurred in rural areas where people and small poultry flocks live in close proximity to each other. Transmission has occurred when bird owners gather birds for transport to market, children play with a backyard flock of infected birds, or when infected birds are handled or butchered and consumed. The number of recorded human cases is rather small compared with the huge number of birds affected and the many opportunities for people to come in contact with sick birds. At this time, this HPAI H5N1 strain has not yet gained the ability to spread from person to person.

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