Monkeypox has been spreading rapidly through non-endemic countries in recent months – but scientists think they’ve noticed something different about this outbreak.
The World Health Organisation declared the virus a global health emergency on Saturday, even though the virus has actually been in circulation in other countries for years.
Monkeypox is endemic within some West African countries and usually passes from rodents to people.
This outbreak has triggered almost 16,500 cases between May and July, with 2,137 confirmed cases in the UK alone. Around 73% of these infections were detected in London.
It is also passing from person to person, and is spreading particularly quickly between gay and bi men, as well as men who have sex with men.
The transmission is not the only way it’s different.
The symptoms differ from previous outbreaks, according to a new study from the British Medical Journal (BMJ), conducted with 197 participants.
Of these participants, all of whom were men, 196 identified as gay, bisexual or men who have sex with men.
Importantly, none of the patients in this study died and no patients required intensive hospital care.
New symptoms
Rectal pain and penile swelling were spotted among the patients in this study – two symptoms which are not usually listed for the virus.
If patients have “extensive penile lesions or severe rectal pain” they “should be considered for ongoing review or inpatient management”, according to researchers.
Solitary lesions and swollen tonsils were also detected. These are not normally noticed in monkeypox cases, and the authors noted that these could be mistaken for other conditions.
Common monkeypox symptoms
All of the patients also showed the most common symptoms:
Lesions on their skin, usually on the genitals or perianal area (near the anus)
Fever
Headaches
Swollen lymph nodes
Muscle aches and pain
Shivering, chills
Exhaustion
Weakness
The monkeypox rash usually starts on the face before moving to the body. It gradually transforms, and can form sores comparable to chickenpox or syphilis before scabbing. The scab falls off but can leave a scar.
The incubation period (the time before symptoms appear) is usually from six to 13 days but can range from five to 21 days.
Other key observations:
Only one of the patients in this study had recently travelled to an endemic region. This suggests that community transmission is becoming much more common with this outbreak of monkeypox.
Only a quarter of patients had known contact with someone with confirmed monkeypox, which authors believe could indicate transmission by people with no or very few symptoms.
The scientists behind the study did note that the data was limited to just a single centre.
They write: “Understanding these findings will have major implications for contact tracing, public health advice, and ongoing infection control and isolation measures.”
They also called for more research to understand how we can control the infection, prevent the spread and guide further treatment.