Monkeypox Symptoms in London Patients Differ from Prior Outbreaks

Human infections with the monkeypox virus have historically been linked to west Africa, where it is endemic. However, since May 2022, there have been nearly 3500 monkeypox cases reported in at least 50 countries.

Sexual health clinics in the United Kingdom and other countries are reporting a rapid spike in monkeypox infections with no clear ties to endemic regions. The first study of the UK’s ongoing monkeypox outbreak, published in The Lancet, found these infected individuals presented with different symptoms than prior monkeypox outbreaks.

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

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

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

The investigators reported that 36 (67%) patients reported fatigue or lethargy, 31 (57%) reported fever, and 10 (18%) had no prodromal symptoms (asymptomatic before the signature monkeypox rash appeared). All patients presented with skin legions, 51 (94%) of which were anogenital; this location of the lesions contributes to the public misconception that monkeypox is an STI.

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

The skin lesions of 37 (89%) of individuals affected more than 1 anatomical site, and 4 (7%) patients had oropharyngeal lesions. Additionally, 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 hospital admission, largely due to pain or localized bacterial cellulitis requiring antibiotic intervention or analgesia. There were no fatalities reported in any study patients.

All but 2 of the patients had not believed themselves to have been in contact with a known case and none reported travel to sub-Saharan Africa, though many had recently traveled to other European countries. Of the patients who responded to the questions on sexual activity, 47 (90%) reported at least 1 new sexual partner during the 3 weeks before they became symptomatic, with 49 reporting inconsistent condom use during this period.

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

The study authors concluded that autochthonous community transmission of the monkeypox virus is continuing to circulate in the UK, largely among MSM. The high rate of concomitant STIs and anogenital symptoms suggests transmission occurred during close skin-to-skin or mucosal contact, such as sexual activity.

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

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