Monkeypox infections could be flying under the radar as symptoms differ from what doctors have seen in the past, according to a study published Friday in Lancet Infectious Diseases, as public health officials in Europe and North America scramble to contain the growing outbreak.
Monkeypox symptoms in recent cases seem to be milder and more localized than what doctors have seen in the past, according to a study of 54 patients from four sexual health centers in London in May.
The patients, all identifying as men who have sex with men, had symptoms and developed a rash, though the group had much higher rates of skin lesions in genital and anal areas, lower rates of fever and fatigue than past outbreaks and nearly a fifth (18%) did not report any symptoms before developing a rash.
Skin lesions—which have previously been documented as covering multiple body areas, especially the limbs, face and neck—were often more localized among the London patients and nearly a third (31%) had lesions only in genital or anal areas.
A quarter of the patients also tested positive for chlamydia or gonorrhea (or both) at the same time as the monkeypox infection, which, combined with the prevalence of lesions in genital and anal areas, suggests the virus was transmitted through close contact during sexual activity, said Dr. Ruth Byrne, a doctor involved with the research from the Chelsea & Westminster Hospital NHS Foundation Trust.
Byrne noted that this finding might not accurately “reflect transmission in the wider population” and could stem from all the researchers being sexual health providers.
What To Watch For
Updated case definitions. Monkeypox has typically been characterized by flu-like symptoms including fever, swollen lymph nodes, body aches and tiredness followed by a diffuse characteristic rash developing across multiple body sites, often the face and limbs. As this study highlights, many of the cases being reported in the U.S., U.K. and Europe during this outbreak are different. Sizable portions report no pre-rash symptoms at all and rashes begin in genital and anal areas, sometimes not spreading elsewhere, and some patients are reported to have had just one or two pox. Byrne said it’s possible the infection “may mimic common STIs, such as herpes and syphilis, in its presentation,” urging clinicians and patients to be vigilant to prevent misdiagnoses.
1 in 6. That’s at least how many patients involved in the study would not have met current criteria for a probable monkeypox case, said Dr. Nicolo Girometti, also from the Chelsea & Westminster Hospital NHS Foundation Trust. Girometti urged officials to review guidelines in light of what clinicians have been seeing with the new outbreak.
Monkeypox has spread for decades in parts of Central and Western Africa, though it has been largely neglected by the rest of the world until multiple cases were found in Europe and North America in May. Its appearance alarmed experts and public health authorities and spurred governments into action to contain the outbreak. Vaccines and treatments are available for monkeypox, though most were developed for its close viral relative, smallpox. Despite having endured outbreaks for decades, nations where the disease is endemic have not received any vaccines yet. The U.S., meanwhile, is prioritizing states with high rates of infection and large numbers of people at risk of severe disease for its vaccine drive. Supplies are limited and the current strategy recommends anyone with a confirmed or suspected exposure get vaccinated, which includes people who have had close physical contact with someone diagnosed with monkeypox, people who know their sexual partner was diagnosed and men who have sex with men who have recently had multiple sex partners in an area where monkeypox is spreading or in a venue where there was known monkeypox case. Though cases are predominantly among gay and bisexual men or men who have sex with men, experts stress that the virus can infect anyone and warn against stigmatizing anyone.
What We Don’t Know
If monkeypox can be transmitted sexually. Though the researchers suspect most patients in the study acquired monkeypox through sexual activity, they caution against labelling the outbreak as sexually transmitted. There is a significant difference between something being passed on through the close contact that accompanies sex and something that can only be acquired in a sexual context, they said, stressing the need for a coordinated response that addresses all ways we know monkeypox to spread. Monkeypox is primarily transmitted through close contact with an infected animal or person or contaminated objects like towels, clothes or bedding. It can also spread via respiratory droplets, which are created when people breathe, cough, talk or sneeze.
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