Monkeypox virus: What is it, how does it spread, and what are the symptoms?

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It's rare for the virus to be seen in Britain and most previous cases here have been linked to travel to other parts of the world
It's rare for the virus to be seen in Britain and most previous cases here have been linked to travel to other parts of the world

Britain is currently experiencing its biggest ever outbreak of monkeypox, with seven known cases.

The UK Health Security Agency (UKHSA) announced on Monday that a cluster of four cases had been reported in England and they are not linked to the three other cases.

Six of these are in London, and one is in the North East, with patients either self-isolating at home or being tended in specialist infectious disease wards at Guy’s and St Thomas, St Mary’s Hospital, the Royal Free Hospital or the Royal Victoria Infirmary in Newcastle.

It is rare for the virus to be seen in Britain and most previous cases on our shores have been linked to travel to other parts of the world where it is more prevalent, particularly West Africa.

However, there is now evidence the virus is spreading in the community as none of the four most recent patients were linked to the other cases or had travelled recently.

The first case was identified in London on May 7 in a patient who had recently returned from Nigeria; the second and third cases lived together in London and were announced a week later on the 14th; and the most recent batch of four (three in London and one in the North East) were revealed on Tuesday.

Health officials do not know how the latest batch four patients caught the virus but are investigating whether it can be passed via sexual intercourse, something that has never been described before for this pathogen.

All four of the most recent cases were men in the LGBTQ+ community and health officials are now urging this group to be particularly aware of “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”.

What is the Monkeypox virus?

The name monkeypox is somewhat misleading as it is a virus that circulates most often in small mammals in Africa, such as rats, which are believed to be the disease’s reservoir.

However, it can also infect monkeys. The condition’s visible lesions and bumps on an afflicted group of research primates in 1958 led to the red herring of a moniker.

It was first discovered in the 1950s and jumped into humans in the 1970s.

“It’s a poxvirus, in the same family as variola virus, which caused smallpox before it was eradicated globally in 1980,” said Dr Michael Skinner, a reader in virology at Imperial College London.

He added that the smallpox vaccine can also protect against monkeypox, but this inoculation was halted in 1971 due to a low level of disease.

Dr Michael Head, a leading global health expert from the University of Southampton, said that with the sophisticated healthcare in the UK, “the risks to the wider public are extremely low”.

The World Health Organisation (WHO) added that there is “minimal” risk of onward spread from an infected person in the UK due to contact tracing and isolation protocols.

How is Monkeypox spread?

Unlike Covid, monkeypox can not spread easily through a population as it requires very close contact.

Routes of transmission from one person to another are via large exhaled droplets and skin-to-skin contact with open sores. It can also be caught from eating or touching infected animals.

“It’s a hard virus to transmit between humans,” said Dr Head.

“It needs very close contact, for example skin-to-skin contact with an individual who is infectious with a monkeypox rash. Between these new cases, there will have been that close contact.”

Prof Paul Hunter, professor in medicine at the University of East Anglia, estimates there is only a 10 per cent risk of a person infecting someone they live with.

It has emerged recently that it is possible the virus is also passed during sexual activity, something never described before.

Experts are divided on this topic, with scientists loath to say it is a new STI. However, some academics say it is possible the virus does spread in this “novel” way, even if it is not its primary route of infection.

“It would not be surprising that sex – which does tend to require close person to person skin contact over a quite wide area of the body – would also enable transmission of monkeypox,” said Prof Hunter.

“Whether or not that is genital-to-genital contact or through other contact is not clear to me, though if pocks occur in the genital area than such sexual transmission is likely. “

What are the symptoms?

Monkeypox has an incubation period of about one to two weeks and illness normally lasts for between two and four weeks with most people recovering on their own.

The UKHSA says the initial symptoms include fever, headache, muscle aches, backache, swollen lymph nodes, chills and exhaustion.

It also produces a distinctive rash, which often starts on the face before spreading across 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.

The WHO says that symptoms can be mild or severe, and lesions can be very itchy or painful.

Health experts are “particularly urging” members of the gay community, especially in London, to be aware of any new blemishes, rashes or lesions, including on their genitalia, as the most recent cases were all men who identify as either gay or bisexual.

Is Monkeypox deadly?

Monkeypox has no cure, but there is a vaccine to prevent the development of the disease.

Most people recover fully within a month but it can be fatal in some cases. The exact mortality rate is unknown but is thought to be between one and 10 per cent.

However, children are at higher risk than adults, and monkeypox during pregnancy may lead to complications, congenital monkeypox or stillbirth, according to the WHO.

Monkeypox rash - Alamy/
Monkeypox rash - Alamy/

Why are gay and bisexual men being asked to come forward?

Gay and bisexual men have been specifically mentioned by the UKHSA because the four most recent cases all identify as members of this community.

The agency is also investigating whether the virus can also be transmitted during sex, and if this is a hitherto unknown mechanism of infection.

Dr Susan Hopkins, chief medical adviser at the UKHSA, said: “We are particularly urging men who are gay and bisexual to be aware of any unusual rashes or lesions and to contact a sexual health service without delay.”

Prof Jimmy Whitworth, professor of international public health at the London School of Hygiene & Tropical Medicine, added: “There is a need to engage with the at-risk community of gay and bisexual men to ensure they know about the presence of this infection and report any sign and symptoms to health facilities.”

Monkeypox has not previously been known as a sexually transmissible virus, but experts believe this latest outbreak may be evidence that it is.

Mateo Prochazka, an STI expert at the UKHSA leading the investigation into monkeypox, said on Twitter: “Close contact between two people (such as during sex) could facilitate transmission – but this has never been described before.

“However, the high proportion of cases in the current outbreak in England that are gay or bisexual (4/7, 57 per cent) is highly suggestive of spread in sexual networks.”

He added that this would mean the virus may be transmitted via sex, but it is not its primary route of transmission, much like shigella.