Intended for healthcare professionals


Monkeypox: Virus DNA is widespread in treatment rooms, study finds

BMJ 2022; 379 doi: (Published 12 October 2022) Cite this as: BMJ 2022;379:o2460
  1. Luke Taylor
  1. Bogota

Healthcare workers treating patients with monkeypox should use personal protective equipment (PPE), regularly disinfect any frequently touched surfaces, and practise hand hygiene to protect themselves from becoming infected, researchers have said, after they found that viral DNA circulated widely in the air in hospital isolation treatment rooms.

“These results suggest that monkeypox virus shed into a hospitalised patient’s environment poses an infection risk that needs to be managed,” said Susan Gould of the Liverpool School of Tropical Medicine, who is an author of the study published in Lancet Microbe.1

She added, “In the context of ward based care, our results support infection prevention and control measures designed to protect against exposure to infectious virus on surfaces and in the air, such as appropriate PPE, as well as applying measures designed to contain shed virus within hospitalised patients’ isolation rooms, including the use of negative pressure rooms and doffing areas.”

More than 70 000 cases of monkeypox and 26 deaths have been confirmed in 108 countries this year, the World Health Organization has reported.2 Most cases were recorded from May this year, when the zoonotic disease spread to many countries that had previously not reported outbreaks.

Although monkeypox is largely transmitted through direct physical contact between two people—largely through skin-to-skin contact with lesions, scabs, or body fluids—healthcare workers treating patients in the UK and the US have contracted the illness.3 In August two Brazilian nurses treating a patient who was infected with monkeypox at their home contracted the disease, probably from contaminated surfaces.4

To determine the risk of the disease’s spread the researchers took samples from frequently touched surfaces, health workers’ PPE, and air samples during bedding changes in isolated rooms of patients with monkeypox at the Royal Free Hospital in London from 24 May to 17 June 2022. Virus DNA shed by the patients was detected on 93% (56/60) of surfaces in the isolation rooms, in five of 20 air samples, and on PPE.

Skin particles

Jake Dunning, a study author and researcher in diseases at the University of Oxford, told The BMJ, “We expected to see a lot of monkeypox virus DNA in the isolation rooms based on what we know about virus shedding by patients with monkeypox, but the relatively low Ct values [monkeypox DNA cycle threshold] and the widespread distribution of DNA within some of the rooms, including the floors, was still a ‘wow’ moment when the results came back.

“We were even more amazed to see that we could capture virus—particularly virus that could be isolated in cell culture—from air samples, as it’s technically challenging to do this.”

The finding that the virus sampled in the air was capable of replicating in cells under laboratory conditions suggests that it could infect other people.

More viral DNA was detected in the air samples taken when bed linen was being changed, suggesting that replacing the sheets of an infected person increases the risk of exposure. It was likely that skin particles were shed into the sheets and then dispersed in the air when they were changed, the researchers said.

Gould said that the detection of live virus in air samples had added to the evidence that particles circulating in the air could be a route of transmission in community or household settings.

“We also know that virus is in shed skin particles and up to 50% of household dust is shed skin cells,” she added. “We often forget that household dust is often stirred up and forms aerosols—those particles we see slowly moving through the air when sunlight shines through a window.”

The fact that so few cases of monkeypox had been detected in healthcare professionals, however, suggested that current safety precautions in hospitals were successfully reducing risk of transmission, the researchers said.

Gould added, “That doesn’t mean that exposure to respiratory droplets or short range respiratory aerosols containing virus is not contributing to transmission when people do have close contact, but the worse disease we see [with the most numerous lesions or most severe lesions] is often in areas that we think were directly exposed to the infectious lesions on skin or mucous membranes of someone with monkeypox.

“The case and outbreak investigations do not suggest that monkeypox spreads like cough, cold, and flu viruses spread.”