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Sexual transmission under investigation as monkeypox cases double

sexual monkeypox

UKHSA is investigating whether sexual transmission is behind a spread in monkeypox in England, as four more cases were identified.

As the UKHSA detected four additional cases, three of which are in London with a fourth ‘linked’ case in the northeast, experts said clinicians needed to be on ‘alert’.

These new cases – which have affected men who have sex with men (MSM) – are in addition to the three that had previously been confirmed by UKHSA and ‘do not have known connections’ with them, it said.

This means there are currently seven confirmed monkeypox cases in the UK, diagnosed between 6 and 15 May.

Those ‘needing medical care’ are being treated in specialist infectious disease units at the Royal Free Hospital, Royal Victoria Infirmary in Newcastle upon Tyne and Guys’ and St Thomas’ – although they have the milder West African strain of the virus, UKHSA said.

It added that ‘investigations are underway’ to establish links between the latest four cases who ‘all appear to have been infected in London’.

It said: ‘All four of these cases self-identify as gay, bisexual or other men who have sex with men (MSM). Currently, common contacts have been identified for two of the four latest cases.  

‘There is no link to travel to a country where monkeypox is endemic and exactly where and how they acquired their infections remains under urgent investigation, including whether they have further links to each other.’

UKHSA advised gay, bisexual and other MSM communities to ‘be alert to any unusual rashes or lesions on any part of their body, especially their genitalia, and to contact a sexual health service if they have concerns’.

It also said that clinicians should be ‘alert’ to individuals presenting with rashes ‘without a clear alternative diagnosis’ and should contact specialist services for advice.

Monkeypox symptoms

Initial symptoms of monkeypox include:

  • Fever
  • Headache
  • Muscle aches
  • Backache
  • Swollen lymph nodes
  • Chills 
  • Exhaustion

A rash can develop, often beginning on the face, then spreading to other parts of the body including the genitals. The rash changes and goes through different stages, and can look like chickenpox or syphilis, before finally forming a scab, which later falls off.

Monkeypox is a viral infection usually associated with travel to West Africa.


UKHSA chief medical adviser Dr Susan Hopkins said: ‘This is rare and unusual. UKHSA is rapidly investigating the source of these infections because the evidence suggests that there may be transmission of the monkeypox virus in the community, spread by close contact.’

Experts warned against the conclusion that the cases acquired the infection via sexual contact as a novel route of transmission.

Dr Michael Skinner, reader in virology at Imperial College London, said: ‘Although the current cluster of cases is in men who have sex with men, it is probably too early to make conclusions about the mode of transmission or assume that sexual activity was necessary for transmission, unless we have clear epidemiological data and analysis. 

‘By nature, sexual activity involves intimate contact, which one would expect to increase the likelihood of transmission, whatever a person’s sexual orientation and irrespective of the mode of transmission.’

Emeritus professor in the epidemiology of infectious diseases at the University of Nottingham, Professor Keith Neal added that ‘further work’ investigating whether the virus is found in semen would be required to say the virus had been ‘truly sexually transmitted’.

Dr Skinner added: ‘Monkeypox seems to require close contact to spread, we’ve seen infection of close family or household members and carers in hospitals, which might also include intimate contact

‘Depending on the stage of infection, close range respiratory or droplet transmission can probably occur. Direct contact with lesions will probably transmit the virus, which might enter by the mouth. When the lesions have healed, the scabs (which might carry infectious virus) can be shed as dust, which could be inhaled.’

The general public ‘have no need for concern but clinicians and public health authorities need to be on alert to spot infected cases early to limit transmission’, he said.

‘Sporadic’ cases must be ‘identified, isolated and their contacts traced’, he added.

And he suggested that factors contributing to cases in ‘recent years’ could include waning immunity following the cessation of smallpox vaccination and that the ‘distribution’ of the virus in West African wildlife has ‘altered in some way’ so that ‘humans are more likely to be infected’. 

UKHSA reiterated that the viral infection is ‘usually a mild self-limiting illness, spread by very close contact with someone with monkeypox and most people recover within a few weeks’.

Monkeypox ‘does not spread easily between people and the risk to the UK population is low’, it said.

It added: ‘Due to the recent increase in cases and uncertainties around where some of these individuals acquired their infection, we are working closely with NHS partners to identify if there may have been more cases in recent weeks, as well as international partners to understand if similar rises have been seen in other countries.’

UKHSA announced on 7 May that it had confirmed a case of monkeypox in England, with the patient believed to have contracted the infection in Nigeria where they had recently travelled from to the UK – followed by a further two on 14 May.

It comes as UKHSA is also investigating an unexplained rise in child hepatitis, where the evidence ‘increasingly’ suggests that adenoviruses are behind the recent increase.


Dylan Summers 18 May, 2022 9:44 am

“All four of these cases self-identify as […] men who have sex with men (MSM).”

Someone’s tying themselves up in linguistic knots in order not to offend.

MSM isn’t something you can choose whether or not to “self-identify” as. The terminology was created precisely to avoid the confusion around “self-identifying”.

Whether you self-identify as straight, gay or Klingon, if you are a man who has sex with men then you are MSM. If you do not have sex with men you are not.