Study finds asymptomatic infection with monkeypox virus

An outbreak of monkeypox (MPVX) was reported in May 2022, primarily affecting men who have sex with men (MSM) with skin lesions characterizing most infections. However, a recent study found three asymptomatic men without any skin lesions to test positive for the anorectal MPXV polymerase chain reaction (PCR) test. Knowing whether MPVX infections can be asymptomatic can be helpful in managing outbreaks.

A new study published in the Annals of Internal Medicine aimed to assess the presence of MPVX in anorectal specimens of MSM who underwent routine testing for sexually transmitted infections from June 5 to July 11, 2022.

Study: Detection of Monkeypox virus in anorectal swabs from asymptomatic men who have sex with men as part of a screening program for sexually transmitted infections in Paris, France. Image Credit: Dotted Yeti / Shutterstock

About the study

The study involved the collection of anorectal swabs from patients who visited the Infectious Diseases Department and Sexual Health Clinic at Bichat-Claude Bernard Hospital in Paris, France, for screening for Chlamydia trachomatis and Neisseria gonorrhoeae. Screening was done every three months and involved MSM with multiple sexual partners living with HIV and receiving treatment or taking HIV pre-exposure prophylaxis (PrEP).

Nucleic acid was extracted from collected samples, followed by MPXV-specific PCR to detect MPVX infection.

Study results

The results indicated that of the 706 MSM who attended the clinic, 383 had symptoms of MPVX infection, while 323 had no symptoms. Two hundred and thirteen anal swabs were collected from patients with no symptoms, and they tested negative for N.gonorrhoeae and C.trachomatis. Of the 213 MSM, 110 patients were diagnosed with HIV 9 years ago and had been receiving antiretroviral therapy since diagnosis. However, 78% of them had an undetectable viral load with a median CD4 T cell count of 0.766 × 10^9 cells/L.

Thirteen samples were found positive for MPVX. Of these, eight were living with undetectable HIV and had CD4 T cell counts greater than 0.500 × 10^9 cells/L. Among them, only one patient reported a CD4 T cell count of 0.123 × 10^9 cells/L. Moreover, most asymptomatic patients never developed clinical symptoms. However, three asymptomatic patients who initially tested negative for MPVX infection developed symptoms and tested positive after three weeks of initial testing.

Therefore, the current study determines that positive results of MPVX infection can occur in asymptomatic patients. However, it is still unclear whether this suggests viral shedding leading to transmission. Recently, French authorities recommended the vaccination of all multipartner MSM to prevent the spread of MPVX infection.

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