False-colour transmission electron micrograph of a cell infected by influenza virus. The cell in this case is a tissue-culture cell (green & yellow); it has been programmed by the virus to produce more virions (red), which it is in the process of releasing. The influenza virus is a 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 result. Magnific- ation: x21'375 at 6x4.5cm size.