Cowpox virus in a 12-year-old boy: rapid identification by an orthopoxvirus-specific polymerase chain reaction

Although smallpox was eradicated 20 years ago, other members of the genus O rthopoxvirus (OPV), such as cowpox virus (CPXV) or monkeypox virus, are sti ll a threat to humans. Because human CPXV infection is rare, it is seldom s uspected on clinical grounds only. We report a boy who presented with two n ecrotic ulcers with surrounding erythema. Infection with OPV was suspected, as antibiotic treatment had not produced improvement and smears were negat ive for anthrax. An OPV was isolated and an OPV-specific polymerase chain r eaction combined with a subsequent restriction enzyme fragment length polym orphism assay confirmed infection by CPXV. Although the patient's cat had h ad no skin lesions, OPV-specific antibodies were found at a titre of 1 : 8 in a plaque reduction assay, suggesting that the cat had transmitted the vi rus to the boy.