Color enhanced transmission electron micrograph (TEM), revealing the ultrastructural details of two avian influenza A (H5N1) virions, a type of bird flu virus, which is a subtype of avian influenza A. At this magnification, one may note the stippled appearance of the roughened surface of the proteinaceous coat encasing each virion. Although this virus does not typically infect humans, in 1997, the first instance of direct bird-to-human spread of influenza A (H5N1) virus was documented during an outbreak of avian influenza among poultry in Hong Kong. The virus caused severe respiratory illness in 18 people, six of whom died. Magnification: 108,000x