Doctors in the United Kingdom are working to contain an outbreak of a new, more easily spreadable strain of the mpox virus.

The virus, which was previously spread mainly through the exchange of bodily fluids, can now be shared through such things as household contact.

UK health officials said this week they have uncovered two additional cases of the new strain in London, among people who shared living space with a man who tested positive after returning from a trip to Central Africa, where the virus is endemic.

After announcing confirmation of the nation's first three cases of the new strain, known as Clade 1b, Professor Susan Hopkins, chief medical adviser at the UK Health Security Agency, or UKHSA, said the strain is more easily transferred but does not amount to a significant risk to the public.

"Mpox is very infectious in households with close contact and so it is not unexpected to see further cases within the same household," she said.

"The overall risk to the UK population remains low. We are working with partners to make sure all contacts of the cases are identified and contacted to reduce the risk of further spread."

Mpox, which was known as monkeypox until the World Health Organization renamed it in November 2022, typically causes flu-like symptoms within a few of days of infection and causes a rash of pus-filled lesions that can persist for up to a month. People infected with the virus often also experience a fever, headaches and a lack of energy. In some cases, it can be fatal.

The previous strain of the mpox virus, Clade 2, caused a public health emergency in the UK in 2022, with the outbreak peaking that July, when there were 1,517 confirmed cases. That outbreak was mainly centered on London, among men who had had sex with other men.

The WHO declared the Clade 1b strain of the virus a global health emergency this summer, after it became endemic in West Africa and Central Africa, in nations including Burundi, the Democratic Republic of Congo, Kenya and Rwanda. Cases attributed to visits to Africa have since been recorded in Germany, India, Sweden, the UK and Thailand.

The UK's Health Minister Wes Streeting said last week that the government is working closely with the UKHSA and the National Health Service "to protect the public and prevent transmission" of the virus.

The WHO and the Africa Centers for Disease Control and Prevention have said Africa has had more than 48,000 suspected cases of Clade 1b so far this year, which they linked to 1,048 deaths.