Coloured transmission electron micrograph (TEM) of a cell infected with influenza virus. The cell, in this case a tissue-culture cell, has been programmed by the virus to produce more virions. They appear here as the red, spherical particles. The cell cytoplasm is coloured yellow. The influenza virus is an RNA orthomyxovirus which has an affinity for mucus. It is spread by coughed or sneezed droplets. Once inhaled, spikes on the virus surface attach it to host cells in the respiratory tract, which it then infects. Influenza is short-lived and usually not serious, although pneumonia may be induced. Magnification: x36,300 at 6x4.5cm size.