Study detects asymptomatic monkeypox virus infection

An outbreak of monkeypox (MPVX) was reported in May 2022, mainly affecting men who have sex with men (MSM) with cutaneous lesions characterizing most infections. However, a recent study highlighted three asymptomatic men without any cutaneous lesions to test positive for the anorectal MPXV polymerase chain reaction (PCR) testing. Knowledge of whether MPVX infections might be asymptomatic can be helpful in epidemic management.

A new study published in the Annals of Internal Medicine aimed to assess the presence of MPVX in the anorectal samples of MSM who had undergone routine tests for sexually transmitted infections from 5th June to 11th July 2022.

Study: Detection of Monkeypox Virus in Anorectal Swabs From Asymptomatic Men Who Have Sex With Men in a Sexually Transmitted Infection Screening Program 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 Disease Department and the Sexual Health Clinic of Bichat-Claude Bernard Hospital in Paris, France, for screening of Chlamydia trachomatis and Neisseria gonorrhoeae. The screening was carried out every three months and involved MSM with multiple sexual partners either living with HIV and getting treatment or taking HIV preexposure prophylaxis (PrEP).

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

Study findings

The results reported that out of the 706 MSM who visited the clinic, 383 had symptoms of MPVX infection, while 323 had no symptoms. Two hundred thirteen anal swabs were collected from patients with no symptoms, and they were found to test negative for N.gonorrhoeae and C.trachomatis. Out 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 undetectable viral load with a median CD4 T-cell count of 0.766 × 10^9 cells/L.

Thirteen samples were found to test positive for MPVX. Out of them, eight were reported to live with undetectable HIV and had a CD4 T-cell count above 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 of the asymptomatic patients never developed any clinical symptoms. However, three asymptomatic patients who had initially tested negative for MPVX infection were reported to develop symptoms and test positive after three weeks of initial testing.

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

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