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Coronavirus particles, coloured transmission electron micrograph (TEM). Coronaviruses cause respiratory infections in humans, including SARS (severe acute respiratory syndrome). SARS is an infectious disease that appeared in China in late 2002, and spread around the world through air travel. It has a mortality rate of around 10%. Other diseases caused by coronaviruses include the common cold, gastroenteritis and pneumonia. The virus particles themselves comprise genetic material surrounded by a protein coat covered with surface proteins. This crown of proteins gives the coronaviruses their name. Magnification unknown. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR GARY GAUGLER)