Health, Canada (Commonwealth Union) – A study led by researchers at Unity Health Toronto, the Sunnybrook Research Institute, and the University of Toronto indicates that DNA from the mpox virus can persist in various body parts for up to four weeks after the onset of symptoms.
Examining samples from 64 men afflicted with mpox, including participants from the Mpox Prospective Observational Cohort Study overseen by Darrell Tan, an infectious disease physician at St. Michael’s Hospital, the researchers discovered varying levels of mpox virus DNA persistence. Notably, they found detectable DNA in almost half of genital skin swabs and one in five skin swabs from other sites a week after symptoms had resolved.
This study, detailed in Open Forum Infectious Diseases, is part of the mpox rapid research response initiated by the Emerging and Pandemic Infections Consortium (EPIC) and its hospital partners during the global mpox outbreak of 2022, formerly referred to as monkeypox.
As per the World Health Organization, there have been nearly 94,000 confirmed cases of mpox across 117 countries since January 2022, resulting in 179 deaths. Canada has reported 1,515 confirmed cases as of September 2023, primarily concentrated in Ontario and Quebec.
“Even though we’ve known about mpox for over 70 years, it was new to us because we hadn’t seen it outside the endemic regions,” explained Robert Kozak, an author of the study as well as a clinical microbiologist at Sunnybrook Research Institute and assistant professor in the department of laboratory medicine and pathobiology at Temerty Medicine. “There was still a lot about the virus and disease that we didn’t know.”
In addressing crucial inquiries regarding viral shedding, Kozak collaborated with Tan and Sharmistha Mishra, an infectious disease specialist at St. Michael’s Hospital and an associate professor within the Temerty Faculty of Medicine’s departments of medicine and Institute of Medical Science, as well as IHPME.
Employing quantitative polymerase chain reaction (qPCR), the team investigated the persistence of mpox virus DNA. Samples were collected from six distinct bodily sites: the genital region, nasal cavity, semen, skin, throat, and urine, over an extended timeframe.
On average, mpox DNA was identifiable in skin swabs from the genital and perianal areas, as well as other skin sites, at 30- and 22-days post-symptom onset, respectively. These results align with the sexually transmitted nature of mpox observed during the recent global outbreak, predominantly affecting gay, bisexual, and men engaging in sexual relations with other men, according to researchers of the study.
The researchers found that a significant portion of semen samples and nasal cavity swabs from individuals showing initial symptoms did not contain viral DNA. Conversely, in urine and throat swab samples, mpox DNA remained detectable for approximately two weeks post-symptom onset.
Notably, there was no discernible variance in the duration of viral DNA persistence between those who were administered the antiviral drug tecovirimat and those who weren’t, according to the researchers. Tan emphasized that while the drug wasn’t randomly assigned to participants, these findings highlight the uncertainty surrounding tecovirimat’s efficacy in treating mpox infections.
Tan further indicated that the study offers valuable insights for clinicians. Initially they have established the range of clinical samples where mpox DNA can be found, aiding in confirming a diagnosis. Additionally, their results emphasize the importance for clinicians to collect such samples from individuals suspected of mpox infection, even after symptoms have subsided, according to him.
However, the researchers caution that the presence of mpox DNA up to four weeks post-symptom onset doesn’t necessarily imply infectiousness for that entire duration.
“We don’t know for sure whether the presence of detectable viral DNA necessarily means that the virus is transmissible to other people, so more research definitely needs to be done to determine definitively the period of infectiousness,” explained Tan.
With the aim in mind, Jacklyn Hurst, a postdoctoral fellow in Kozak’s laboratory, has initiated research at the Toronto High Containment Facility to investigate the presence of live virus in the identical samples where mpox DNA was identified. Additionally, the researchers are utilizing the facility’s biobank of mpox patient samples to pinpoint biomarkers that might forecast whether an individual will experience a mild or severe infection.
“Without the Toronto High Containment Facility, we wouldn’t be able to do any of this. Having that facility will help us answer a lot of questions about this virus and how to stop it,” added Kozak.
