Symptoms of monkeypox in London patients differ from previous outbreaks

Human infections with monkeypox virus have historically been linked to West Africa, where it is endemic. However, since May 2022, nearly 3,500 cases of monkeypox have been reported in at least 50 countries.

Sexual health clinics in the UK and other countries are reporting a rapid increase in monkeypox infections with no clear link to endemic regions. The first study into the ongoing monkeypox outbreak in the UK, published in The Lancetfound that these infected people showed different symptoms than in previous monkeypox outbreaks.

The study analyzed the demographic and clinical characteristics of people diagnosed with human monkeypox virus during a sexual health center visit.

The observational analysis included 54 patients who tested positive for monkeypox at open-access sexual health clinics in London, UK, from May 14-25, 2022. Thus, investigators reported hospitalizations and any pre-existing sexually transmitted infections (STIs) during the first 2 weeks of this monkeypox outbreak.

The 54 patients included were identified as men who have sex with men (MSM) and were on average 41 years old. A total of 38 (70%) were Caucasian, 26 (48%) were born in the UK and 13 (23%) were living with HIV infection.

Investigators reported that 36 (67%) patients reported fatigue or lethargy, 31 (57%) reported fever, and 10 (18%) had no prodromal symptoms (asymptomatic before the onset of characteristic rash of monkeypox). All patients had cutaneous lesions, of which 51 (94%) were anogenital; this location of lesions contributes to the public misconception that monkeypox is an STI.

“The commonly observed symptom of skin lesions in the anal and penile regions, and the fact that a quarter of patients tested positive for gonorrhea or chlamydia concurrently with monkeypox infection, suggest that transmission of the The monkeypox virus in this cohort is occurring skin-to-skin close together, for example through sexual activity,” said Dr Ruth Byrne, MBBS, of Chelsea and Westminster Hospital NHS Foundation Trust. “However, this finding may be biased by the fact that we are sexual health providers and therefore may not reflect transmission in the wider population.”

Skin lesions in 37 (89%) of individuals affected more than one anatomical site, and 4 (7%) patients had oropharyngeal lesions. In addition, 30 (55%) of the study cohort had lymphadenopathy and 1 in 4 had a concurrent STI. A total of 5 (9%) of the 54 patients required hospitalization, mainly due to pain or localized bacterial cellulitis requiring antibiotic therapy or analgesia. No deaths were reported in the study patients.

All but 2 of the patients did not believe they had contact with a known case and none reported having traveled to sub-Saharan Africa, although many had recently traveled to other European countries. Of patients who answered questions about sexual activity, 47 (90%) reported having had at least 1 new sexual partner in the 3 weeks prior to symptom onset, and 49 reported inconsistent condom use during this period.

Overall, patients in this study had a higher prevalence of skin lesions around the genital and anal areas, and a lower prevalence of fatigue and fever than in previously studied monkeypox outbreaks.

The study authors concluded that indigenous community transmission of monkeypox virus continues to circulate in the UK, primarily among MSM. The high rate of STIs and concurrent anogenital symptoms suggests that transmission occurred through close skin-to-skin or mucous membrane contact, such as sexual activity.

“It is possible that at different stages of infection, monkeypox may mimic common STIs, such as herpes and syphilis, in its presentation,” Byrne noted. “It is important for sexual health clinicians and patients to be aware of the symptoms of monkeypox, as misdiagnosis of the infection can preclude appropriate intervention and prevent onward transmission. Additional resources are urgently needed to support services in managing this condition.

Byrne and the investigators recommended further study of viral transmission pathways to better inform monkeypox infection control policies, educational efforts, contact tracing and prevention strategies.

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