Huge study of monkeypox patients reveals common symptoms, from fevers to small lesions

• A first-of-its kind study of monkeypox patients around the world reveals some of the most common symptoms.
• Some patients have only one single lesion, making it hard to diagnose the virus.

A groundbreaking new study of more than 500 monkeypox cases diagnosed around the globe suggests the disease is being missed and misdiagnosed frequently, as testing and vaccinations lag. Case studies in the report, which come from roughly 100 different clinicians stationed around the world, reveal some of the most common symptoms of monkeypox in the current outbreak may not always line up with what people expect to see.

"Most people have never had any training on monkeypox," lead study author Chloe Orkin, a professor of HIV Medicine at Queen Mary University of London, told Insider. "The important thing is to help doctors to recognize it, so they don't mistake it for a sexually transmitted infection."

Orkin's study, published in the New England Journal of Medicine on Thursday, found that among 528 monkeypox patients identified in 16 countries between April and June, rashes were common (occurring 95% of the time). Some 73% of patients had anogenital lesions, while roughly 10% of patients had only one monkeypox lesion visible on them. 98% of the patients, who all agreed to be in the study, were gay or bisexual men, reflecting the fact that much of the monkeypox transmission in this outbreak has happened during sexual contact.

Some patients had trouble swallowing, or going to the toilet

Cases ranged from very mild to so debilitatingly painful that it became impossible for the patients to use the toilet or swallow, Orkin said.

"People weren't only presenting the skin problems," she added, which is different from how the virus has been characterized in past outbreaks. "They were also presenting with problems inside the anus and inside the mouth. And sometimes these problems were so serious that people were having to be admitted to hospital for pain."

Symptoms of monkeypox infection that showed up before people developed a rash included fevers (in 62% of patients), lethargy (41% of the time), muscle aches (31%), and headaches (27%). Among 70 patients who were hospitalized from the study, the most common issues patients had were severe anorectal pain (21 patients), skin infections (18 patients), and trouble swallowing (five patients).

Early treatment is critical, not only to help contain the virus, but also because the antiviral treatments that are available work best when administered early on in the course of an infection.

"It can easily be missed," Orkin said. "And it does look as though it has been missed."

Dr. Lilian Abbo, from the University of Miami, expressed frustration during an Infectious Diseases Society of America phone call last week that some patients in South Florida had to schedule multiple visits with different providers before they finally received a positive monkeypox diagnosis.

At least 2,323 monkeypox cases have been diagnosed so far in the US, according to the Centers for Disease Control and Prevention, and the World Health Organization estimates that monkeypox is present in at least 50 countries around the world.

Clinicians aren't sure whether the monkeypox that is circulating now is truly a different kind of virus than they've seen in the past, or whether the different presentations of the virus being seen now are more reflective of how monkeypox is being passed from person to person (through skin to skin touching during sexual contact.)

Though monkeypox DNA was detected in the semen of some of the patients tested in this study, it's still unclear what that find might mean for potential sexual transmission of this virus.

"You can find virus in semen, but it doesn't necessarily mean that it's a public health concern," Dr. Lawrence Purpura, an infectious disease expert at Columbia University Irving Medical Center, said.

Purpura, who was not involved in this research and has studied viruses in semen including Ebola and COVID, said "just detecting a virus doesn't immediately raise the red flags that we should be worried about sexual transmission at this point, but it does, I think, give enough impetus to really study it — and study it quickly, to figure out if that is a potential risk."