Another 36 monkeypox cases have been detected in the UK, taking the total to 56.
All the new infections are in England, while Scotland announced its first case earlier today.
Health officials said that while the outbreak is “significant and concerning”, the risk to the UK population remains low.
It comes as experts on the continent warned there is a risk the rare virus could be passed from humans to animals and it may become endemic in Europe.
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At least 85 confirmed cases have been identified in eight EU countries, including Belgium, France, Germany, Italy, Netherlands, Portugal, Spain, and Sweden, between 15 and 23 May.
Dr David Heymann, who chairs a World Health Organisation (WHO) expert group, has described the unprecedented outbreak in Europe as “a random event” that might have been spread by sexual transmission among gay and bisexual men at two raves in Spain and Belgium.
The UK Health Security Agency has warned that high-risk close contacts of confirmed monkeypox cases should self-isolate for 21 days.
A large proportion of cases has been identified in the gay, bisexual and men who have sex with other men community.
Monkeypox is not normally a sexually-transmitted infection, but it can be passed on by direct contact during sex.
It can also be spread through touching clothing, bedding or towels used by someone with the monkey rash, and through the coughs and sneezes of somebody with the infection.
Read more:
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Monkeypox has not previously triggered widespread outbreaks beyond Africa, where it is endemic in animals.
Callum Semple, professor of outbreak medicine at the University of Liverpool, told Sky News: “It’s previously been the case that the virus has moved from animals to humans and contaminated implements and foodstuffs, mainly in Africa. It looks like the virus has found a particular niche, exploiting features of human behaviour, and that’s allowed it to become established in this group of people.
“On the plus side, because the virus has a relatively long incubation period and the symptoms are cutaneous, there is the opportunity for contact tracing to identify people and break these chains of transmission.”
‘Mild disease symptoms’
The European Centre for Disease Prevention and Control (ECDC) said most of the cases in Europe have “mild disease symptoms” and are among men who have sex with men, with the likelihood of spread among the broader population “very low”.
But the ECDC director, Andrea Ammon, warned: “The likelihood of further spread of the virus through close contact, for example during sexual activities among persons with multiple sexual partners, is considered to be high.”
The centre warned that if human-to-animal transmission occurs, and the virus spreads in an animal population, there is a risk the disease could become endemic in Europe.
It urged close collaboration between human and veterinary public health authorities to manage exposed pets and prevent the disease from being transmitted to wildlife.
The ECDC also warned monkeypox can cause severe disease in certain population groups, such as young children, pregnant women and immunosuppressed people.
The UK government has ordered in several thousand doses of the smallpox vaccine, understood to be about 85% effective against monkeypox. It is offering the jab to very close contacts of those who have been affected.
Public health officials in Scotland have stockpiled a “small number” of shots.
Belgium has reportedly introduced a 21-day quarantine for those who contract monkeypox after four infections were recorded in the country.
The World Health Organisation said it does not have evidence that monkeypox has mutated, adding the infectious disease which is endemic in west and central Africa has tended not to change.
Early signs
Initial symptoms include fever, headache, muscle aches, backache, swollen lymph nodes, chills and 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.
The ECDC said infected persons should remain isolated until scabs fall off and should especially avoid close contact with immunosuppressed people and pets.