Investigation of the First Laboratory-Acquired Human Cowpox Virus Infection in the United

Background. Cowpox virus is an Orthopoxvirus that can cause infections in humans and a variety of animals. Infections occur in Eurasia; infections in humans and animals have not been reported in the United States. This report describes the occurrence of the first known human case of laboratory-acquired cowpox virus infection in the United States and the ensuing investigation. Methods. The patient and laboratory personnel were interviewed, and laboratory activities were reviewed. Real-time polymerase chain reaction (PCR) and serologic assays were used to test the patient’s specimens. PCR assays were used to test specimens obtained during the investigation. Results. A specimen from the patient’s lesion tested positive for cowpox virus DNA. Genome sequencing revealed a recombinant region consistent with a strain of cowpox virus stored in the research laboratory’s freezer. Cowpox virus contamination was detected in 6 additional laboratory stocks of viruses. Orthopoxvirus DNA was present in 3 of 20 environmental swabs taken from laboratory surfaces. Conclusions. The handling of contaminated reagents or contact with contaminated surfaces was likely the mode of transmission. Delays in recognition and diagnosis of this infection in a laboratory researcher underscor