Adenoviruses. Coloured transmission electron micrograph (TEM) of adenovirus particles. The viruses have icosahedral (20-sided) protein coats, or capsids, formed from protein subunits called capsomers (orange dots). Within each protein coat is DNA (deoxyribonucleic acid) genetic material, while covering the capsid are proteins (not seen) which allow the virus to infect its target cell. Adenoviruses cause upper respiratory tract infections, with symptoms usually resembling those of the common cold. They are also associated with diarrhoea in children and eye infections such as conjunctivitis. Magnification: x200,000 at 6x7cm size.