While virus persists for several months in the spleens of infected mice, it is shed in the feces for only about 3 weeks. Multiple strains of ectromelia virus exist, with the Moscow strain being most virulent. Natural infection of laboratory mice with ectromelia virus would severely compromise most research efforts involving mice. Relatively little is known of the natural biology of H-1 virus, and its significance is low in rats, the natural host, since natural infection does not cause clinical disease and effects on research are few. The primary importance of H-1 virus is as a model for experimentally produced malformations in the CNS and skeletal system of rats.
Transmission is via exposure to infectious urine, feces, nasal secretions, and milk.
Natural infection with H-1 virus does not cause disease. However, pathologic changes observed in experimental H-1 virus infection derive from the need for parvoviruses to infect replicating cells, wherein they are lytic. In spite of the paucity of data incriminating H-1 virus as a confounder of research, natural infection of laboratory rats could alter studies of fetal development. More is known of the natural biology of KRV than of H-1 virus. Transmission is via direct contact with infectious urine, feces, nasal secretions, and milk or by contact with contaminated fomites.