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Identifying Monkeypox Viral DNA in Bodily Fluid Samples

Investigators found potentially infectious monkeypox virus DNA in saliva and semen.

Since May 2022, over 9000 cases of monkeypox have now been confirmed in over 57 nonendemic countries. The virus is known to be transmitted by direct skin-to-skin contact with the lesions of an infected person. However, it is unclear whether the monkeypox virus is present in other biological samples, such as saliva, semen, or urine.

One study, published this week in Eurosurveillance, sought to characterize viral shedding to increase understanding of the role of different body fluids in disease transmission. The investigators analyzed saliva, rectal, nasopharyngeal, semen, urine, and fecal samples for monkeypox viral DNA.

"A couple of previous studies had already shown occasional presence of viral DNA in some samples and in some patients, but here we show that viral DNA is frequently present in various biological fluids, particularly saliva, during the acute phase of the disease, and up to 16 days after the onset of symptoms in 1 patient," said Aida Peiró-Mestres, the first author of the study.

From May-June 2022, patients who presented at a Barcelona hospital with a clinical suspicion of monkeypox were examined in isolation. The study cohort included 12 young men who have sex with men (MSM); their average age was 38.5 years. From each patient, the investigators collected samples from 2 different lesions. They also screened for sexually transmitted infections (STIs), including Neisseria gonorrhoeae/Chlamydia trachomatis/Mycoplasma genitalium in pharynx, urine, and rectum by PCR test, Treponema pallidum/Lymphogranuloma venereum/herpes in genital-anal ulcers by PCR test, and hepatitis B virus (HBV)/hepatitis C virus (HCV)/HIV/syphilis by serology.

Most of the patients (9/12) had a previous history of STIs, and 3 had a concomitant STI. Additionally, 4 were HIV-positive, all with undetectable HIV viral load CD4+ T-cell counts between 400 and 860 cells/uL. When possible, follow-up samples were obtained from the patients at multiple time points.

All the patients had been sexually active with up to 10 sexual partners in the last month, and 7 were taking HIV pre-exposure prophylaxis (PrEP). Sexual contact with an individual with monkeypox infection was confirmed in 4 patients. Of the 12 participants, 3 reported recent travel to other parts of Spain, but none had travelled to the Canary Islands or Madrid, where monkeypox cases first appeared in Spain.

An unspecified systemic syndrome, such as fever, myalgia, general malaise, was reported in 11 of 12 patients. Virus genetic material was detected in the skin lesions of all 12 participants. High viral loads were observed in the skin pustules of 9 individuals, with some patients having additional oral, pharyngeal, and rectal lesions. In half of the patients, skin lesions were present in multiple locations on the body.

Monkeypox DNA was detected in the saliva of all patients, as well as in the rectal samples of 11 patients, nasopharyngeal samples of 10 patients, semen samples of 7 patients, urine samples of 9 patients, and fecal samples of 8 patients.

Notably, the presence of viral DNA does not necessarily mean infectious virus; the next step for this research will be trying to isolate infectious virus from the bodily fluid samples. However, the high viral load detected in saliva and semen suggests these fluids have infectious potential: “The results of our study contribute to a better understanding of the mechanisms and dynamics of virus transmission, as well as the possible role of sexual transmission,” said Mikel Martinez, ISGlobal researcher and team lead of the study.