Parvovirus particles. Coloured transmission electron micrograph (TEM) of virus particles (orange) clustered around a piece of cell membrane (purple, centre). These particles belong to the Parvoviridae family, which includes the smallest known viruses and some of the most environmentally resistant. Each particle consists of a single-stranded deoxyribonucleic acid (DNA) genome surrounded by an icosahedral protein capsid. Many virus particles belonging to this family have been associated with outbreaks of gastroenteritis, although a causative role in human disease cannot always be established. Magnification: x186,000 when printed 10 centimetres high.