Does human infection with H5N1 happen often?

No. Only very rarely. The first documented human infections with the H5N1 avian strain occurred in Hong Kong in 1997. In that first outbreak, 18 persons were hospitalized and 6 of them died. The source of infection in all cases was traced to contact with diseased birds on farms (1 case) and in live poultry markets (17 cases).

The human cases coincided with outbreaks of highly pathogenic H5N1 avian influenza in poultry. Very limited human-to-human transmission of the H5N1 strain was documented in health care workers, family members, poultry workers, and workers involved in culling operations. Though H5 antibodies were detected in these groups, indicating infection with the virus, no cases of severe disease occurred as a result. Antibodies were detected in 10% of the poultry workers studied, and in 3% of the cullers.

In February 2003, the H5N1 strain again jumped from birds to infect two members of a family (a father and his son) when they returned to Hong Kong following travel in southern China. The father died but the son recovered. A third member of the family, the boy’s sister, died of a severe respiratory illness in China. No samples were available for determining the cause of her death.