Transmission electron micrograph of parvovirus H-1 virions of the Parvoviridae family of DNA viruses. These are some of the smallest viruses found in nature, consisting of a single-stranded DNA genome surrounded by an icosohedral protein capsid (coat). Parvoviruses replicate most extensively in tissues undergoing relatively rapid division. Disease is therefore often related to gut epithelium (causing enteritis in cats, dogs and mink) or bone marrow (causing panleucopenia in cats).