Content area
Full Text
Monkeypox virus (MPXV) is an enveloped, double-stranded DNA virus in the family Poxvirus, genus Orthopoxvirus, and is related to variola, the causative agent of smallpox. In 2022, MPXV transmission caused a large global mpox disease outbreak that disproportionately affected male persons who identified as gay, bisexual, and men who have sex with men (MSM) and persons who identified as transgender (1). The clinical manifestations of MPXV infection also evolved from prior outbreaks; more patients in 2022 had anogenital rash and proctitis, rather than disseminated cutaneous lesions (1). During prior mpox outbreaks, asymptomatic or subclinical MPXV infection was thought to be rare, but evidence from the 2022 outbreak suggests that infected patients can have minimal symptoms (2,3). To identify persons with subclinical MPXV infection, we retrospectively analyzed oropharyngeal and rectal swab samples submitted for Chlamydia trachomatis and Neisseria gonorrhoeae (CT/NG) testing at a tertiary academic medical center.
Swab samples were collected at Stanford Health Care by using the Aptima Multitest Swab Specimen Collection Kit for the Aptima Combo 2 Assay (Hologic, https://www.hologic.com). We included all samples collected during July 7–September 6, 2022 that had sufficient residual volume. The study was approved by the Stanford University institutional review board (protocol no. 66786).
We extracted total nucleic acids from 300 μL of Aptima Specimen Transport Medium (Hologic) by using the Chemagic instrument (PerkinElmer, https://www.perkinelmer.com), according to the manufacturer’s recommendations. To test for MPXV DNA, we used 2 laboratory-developed quantitative PCR (qPCR) assays modified from Centers for Disease Control and Prevention published assays (4,5). The first qPCR targeted viral DNA polymerase sequence conserved throughout nonvariola orthopoxviruses, including MPXV. The second qPCR targeted the viral tumor necrosis factor (TNF) receptor sequence specific for...