Infection of a child in Hong Kong by an influenza A H3N2 virus closely related to viruses circulating in European pigs

Influenza virus All-long Kong/1774/99, isolated from a young child with mil d influenza, was shown to be similar in its antigenic and genetic character istics to H3N2 viruses circulating in pigs in Europe during the 1990s and i n particular to be closely related to viruses isolated from two children in the Netherlands in 1993, Similar viruses had previously not been identifie d outside Europe. Although there is little evidence as to how the child con tracted the infection, it appears likely that pigs in southern China were t he source of infection. Characteristics shared with the European swine viru ses include resistance to the anti-influenza drugs amantadine and rimantadi ne. Thus not only does this incident once again highlight the potential of pigs as a source of novel human influenza viruses, but also indicates the p otential for emergence of amantadine-resistant human viruses.