Updates by Carol A. Kemper, FACP

Human-to-Human Transmission of Avian Flu

Source: Bridges CB, et al. J Infect Dis 2000;181:344-348.

A central concern during the outbreak of avian influenza (H5N1) among humans in Hong Kong in 1997 was the possibility of human-to-human transmission which could lead to a larger pandemic. This retrospective surveillance study investigated whether 217 health care workers (HCWs) exposed to at least one patient hospitalized were at risk of H5N1 viral infection compared with 309 non-exposed HCWs. No difference in the frequency of poultry exposure was found between the two groups. Antibody to H5N1 virus was found in 10 HCWs, including eight (3.7%) with exposure to a hospitalized patient vs. two (0.7%) non-exposed HCWs. Two HCWs with exposure had evidence of seroconversion in paired serum samples—neither reported exposure to poultry. One of these reported a respiratory illness within two days of exposure to a case, although viral cultures remained negative.

Although paired specimens were not available from all exposed HCWs, these data strongly support the limited occurrence of human-to-human transmission of avian influenza during the outbreak in Hong Kong.