Parvovirus particle. Molecular model showing the structure of the capsid (outer protein coat) of a human parvovirus (family Parvoviridae) particle. Parvoviridae viruses include the smallest known viruses and some of the most environmentally resistant. Each particle consists of a single-stranded deoxyribonucleic acid (DNA) genome (not shown) 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.