METHODS: The patient was interviewed to ascertain potential exposures and identify contacts. Swabs of a papulovesicular lesion on the patient’s back were cultured; DNA fragments amplified from the resulting isolate by quantitative real-time polymerase chain reaction (qPCR) were sequenced and compared with those from described Orthopoxviruses. Sera collected from the patient and contacts were tested for Orthopoxvirus antibodies. Household environmental samples including swabs of surfaces, clothing, personal effects and small mammal feces were tested by using qPCR.
RESULTS: Phylogenetic analysis of sequences from the cultured isolate confirmed a novel Orthopoxvirus species. Patient’s serum was positive for IgM and IgG antibodies, consistent with recent Orthopoxvirus infection. Sera from all 4 contacts were IgM-negative; sera from 2 contacts were IgG-positive, consistent with their prior history of smallpox vaccination. The patient had not recently travelled outside Alaska. Wild rodents were reportedly abundant around, and occasionally found inside, the patient’s home. None of the 23 environmental samples tested positive. No additional human cases were identified.
This investigation identified a novel species of Orthopoxvirus in an Alaska resident whose travel history was inconsistent with importation of the virus into the state. Given Orthopoxviruses emergence in the absence of routine smallpox vaccination, Orthopoxvirus testing should be performed on persons with an illness consistent with poxvirus infection.