Monkeypox could become entrenched in Europe forever if the current outbreak jumps to pets, UK health officials have warned as cases in Britain triple to 57.
All but one of the UK cases are in England, with the UK Health Security Agency announcing on Monday the identification of 36 more infections in England to go with the 20 previously known patients.
One person with monkeypox has also been found in Scotland, but there are no known cases in Wales or Northern Ireland.
Health officials insist the risk to the population remains low but experts believe there is an urgent need to ensure animals do not contract the virus as they could become permanent reservoirs of disease.
No cases have been reported in pets at this point, but in a rapid risk assessment on Monday, the European Centre for Disease Control warned that it was important to "manage exposed pets and prevent the disease from being transmitted to wildlife".
"If human-to-animal transmission occurs, and the virus spreads in an animal population, there is a risk that the disease could become endemic in Europe," the update said.
"Rodents, and particularly species of the family of Sciuridae (squirrels) are likely to be suitable hosts, more so than humans, and transmission from humans to (pet) animals is theoretically possible," the report reads.
"Such a spill-over event could potentially lead to the virus establishing in European wildlife and the disease becoming an endemic zoonosis. The probability of this spill-over event is very low."
Prof David Robertson, of the Glasgow Centre for Virus Research, told the Telegraph this was a "valid concern".
Experts believe rodents, such as rats and squirrels, can harbour the virus but the full range of susceptible animals remains unknown, and could include domesticated pets.
"It would seem sensible to monitor any animals/pets that infected people are in contact with," Robertson added.
A "notable proportion" of the current cases are in gay and bisexual men and this community is being urged to be vigilant to any new rashes or lesions appearing on their body.
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.
Initial symptoms of monkeypox 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.
A person is infectious until after their scabs have dropped off, which can take until several weeks after infection.
Close contacts of infected people in Britain are being offered a smallpox jab called Imvanex to protect them against the disease.
This strategy, known as ring vaccination, includes healthcare workers, sexual partners, flat mates and even a person that a positive case shared a car with.
High-risk contacts are also being asked to isolate at home for three weeks, as the virus has a long incubation time and it can take several weeks for symptoms to emerge.
The vaccine, if administered within four days of exposure, is thought to be highly effective at fighting the monkeypox virus.
Around a third of the nation's 3500 dose-strong stockpile of the vaccine has now been shipped out to NHS Trusts to ensure jabs can be dished out as soon as they are needed.
Dr Susan Hopkins, chief medical adviser at the UK Health Security Agency, said: "Because the virus spreads through close contact, we are urging everyone to be aware of any unusual rashes or lesions and to contact a sexual health service if they have any symptoms.
"A notable proportion of recent cases in the UK and Europe have been found in gay and bisexual men so we are particularly encouraging these men to be alert to the symptoms."
Since the beginning of the monkeypox outbreak at the start of May scientists have found the virus is spreading in sexual networks and likely originated from a single point before being carried globally after people attended internationally advertised gay parties, raves and saunas.
A paper published on Monday by a team of Portuguese academics shows the current global spate of cases "most likely" all came from a single point before propagating worldwide.
The team, led by the National Institute of Health in Lisbon, found that the genetic fingerprint of the current outbreak diverges "far more than one would expect" when compared with previous cases.
The paper's authors add that the theory of the monkeypox being a "hypermutated virus" borne out of an "evolutionary jump" can not be discarded.
"We have already detected the first signs of microevolution within the outbreak cluster," they wrote.