Novel Orthopoxvirus Infection in an Alaska Resident

Abstract

Background.: Human infection by orthopoxviruses is being reported with increasing frequency, attributed in part to the cessation of smallpox vaccination and concomitant waning of population-level immunity. In July 2015, a female resident of interior Alaska presented to an urgent care clinic with a dermal lesion consistent with poxvirus infection. Laboratory testing of a virus isolated from the lesion confirmed infection by an Orthopoxvirus.

Methods.: The virus isolate was characterized by using electron microscopy and nucleic acid sequencing. An epidemiologic investigation that included patient interviews, contact tracing, and serum testing, as well as environmental and small-mammal sampling, was conducted to identify the infection source and possible additional cases.

Results.: Neither signs of active infection nor evidence of recent prior infection were observed in any of the 4 patient contacts identified. The patient's infection source was not definitively identified. Potential routes of exposure included imported fomites from Azerbaijan via the patient's cohabiting partner or wild small mammals in or around the patient's residence. Phylogenetic analyses demonstrated that the virus represents a distinct and previously undescribed genetic lineage of Orthopoxvirus, which is most closely related to the Old World orthopoxviruses.

Conclusions.: Investigation findings point to infection of the patient after exposure in or near Fairbanks. This conclusion raises questions about the geographic origins (Old World vs North American) of the genus Orthopoxvirus. Clinicians should remain vigilant for signs of poxvirus infection and alert public health officials when cases are suspected.

Keywords: Alaska; North America; Orthopoxvirus; lesion; phylogenetics..

Figure 1.

A, B, Patient’s lesion on 29 July 2015 (A) and 20 August 2015 (B). C–E, Electron microscopic images of the virus isolated from the patient showing crescents (C), spherical immature virus in virus factories (D), and A-type inclusion bodies occluded with mature virus in infected cells (E ).

Figure 2.

Results of Bayesian phylogenetic inference, indicating the position of AK2015_poxvirus within the genus Orthopoxvirus. Analysis was based on 9 genes located within the central, conserved region of the genome (Vaccinia virus Copenhagen strain homologues A7L, A10L, A24R, D1R, D5R, E6R, E9L, H4L, and J6R).