Dutch study finds no evidence of monkeypox transmission before May 2022

In a preprint study, Dutch researchers report finding no evidence of widespread human monkeypox virus (hMPXV) transmission in Dutch sexual networks of men who have sex with men (MSM) before May 2022. The study, which is not yet peer-reviewed, is published on medRxiv.

Researchers performed a retrospective study of 401 anorectal and ulcer samples from visitors of sexual health clinics in Rotterdam and Amsterdam dating back to Feb 14, 2022. Swabs are routinely taken when testing for gonorrhea or chlamydia. Samples are kept for an average of 4 to 6 months.

The earliest monkeypox cases identified in the study sample were from the first week of May 2022, the same week the United Kingdom, Spain, and Portugal identified initial cases.

"These findings suggest that the introduction of MPXV in Dutch sexual networks of MSM started somewhere at the end of April 2022. This coincides with the earliest symptom onset of hMPXV cases in the UK on April 21," the authors concluded. Widespread undetected transmission before the first week of May is unlikely.

Today, the global monkeypox total is 80,611 cases, 53 of them fatal, from 110 countries. Approximately 20,000 cases have been reported in Europe. The Netherlands has reported more than 1,200 cases, with a crude notification rate of 70.7 per million population, making it one of the top 5 European countries most affected during the global outbreak.

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