People infected with monkeypox may be infectious long after their scabs and rashes have disappeared, according to new data.
It has long been believed that monkeypox patients, who develop infectious lesions on their body, stop being infectious as soon as their scabs have healed and dropped off.
But analysis from NHS doctors shows this may not be the case as the virus was detected in throat swabs and blood samples long after the rash had vanished.
A study published in the Lancet Infectious Diseases reports on the disease progression of seven people who had monkeypox in Britain between 2018 and 2021.
These cases were all linked to travel to Africa, with one healthcare worker catching the disease after changing an infected person’s bed sheets. This instance was the first time there had been human-to-human transmission of the virus outside Africa.
None of the cases, including the one child, died or needed intensive care treatment but some were admitted to hospital as a precaution to prevent any onward transmission.
The study did not look at the current outbreak, which now totals 71 cases in Britain, with the majority catching it in the community, and a “notable proportion” in gay and bisexual men.
Study author Dr Hugh Adler, an NHS junior doctor in infectious diseases and a research fellow at the Liverpool School of Tropical Medicine, said: “We hope [our study] informs the doctors and public health officials looking after cases now.
“We were surprised to see that you can detect the virus in a throat swab and in blood for this duration of time. We can see that it remains positive in the throat and blood for the length of the illness and maybe even longer after the rash is resolved,” he said.
“Now, we don’t know what this means. We don’t know that this means these patients are more infectious or infectious for longer, but it does inform us of the biology of disease.
“Since we don’t know the implications of it, it’s an important area for future research.”
He added that the current outbreak, which is 10 times bigger than the number of cases from the past three years combined, might provide crucial data to build on this study’s preliminary findings to see if a person can be infectious for longer than their rash persists.
“Traditional guidance, for example from the CDC and other countries, would say that once the rash has got better, the patient is no longer infectious,” Dr Adler explained.
“Because we detected the virus in things like throat swabs, it poses the question of whether people could be infectious for longer and that’s what the future research is to confirm.
“It’s something that we hoped to refine as our knowledge grows in the current outbreak.”
Childhood cases are rare
Dr David Porter, paediatric infectious diseases consultant at Alder Hey Children’s NHS Foundation Trust, also urged parents to not be overly concerned about the outbreak as childhood cases in the UK are rare.
If a parent spots a rash or blemish on their child, the chances are that it is not monkeypox, but chickenpox, he said.
“As a parent, I wouldn’t be encouraging people to be trying to differentiate between monkeypox and chickenpox,” he said.
The study also found promising signs that an antiviral drug designed to target smallpox also shortens a patient’s length of illness and infectiousness, but this was tested in just one case and needs to be backed up with blogger studies.
Fourteen more monkeypox cases were reported in England on Tuesday, taking the UK’s total to 71.
All but one of the infections are in England, with one case identified on Monday in Scotland and no known infections so far in Wales or Northern Ireland.
The UK Health Security Agency (UKHSA) insists the risk to the UK-wide population remains low despite the surging case numbers.
Where in the UK the cases are remains unknown, as does the breakdown by gender and exactly how many people self-identify as gay or bisexual.
If a person notices an unusual blemish on their body, especially on their genitalia, they are being asked to contact NHS 111 immediately or their local sexual health clinic.
Dr Susan Hopkins, Chief Medical Adviser at UKHSA, said: “We are continuing to promptly identify further monkeypox cases in England through our extensive surveillance and contact tracing networks, our vigilant NHS services, and thanks to people coming forward with symptoms.”