Two more UK cases of a strain of mpox that is thought to spread more easily have been detected in household contacts of the first case, the Health Security Agency (UKHSA) has said.

This brings the total number of confirmed cases of the Clade Ib mpox strain in the country to three.

The UKHSA said the risk to the UK population “remains low” and that the two patients are under specialist care at Guy’s and St Thomas’ NHS foundation trust in London.

The first case was detected in London last week in a person who had been on holiday in Africa and travelled back to the UK on an overnight flight on 21 October.

They developed flu-like symptoms more than 24 hours later and, on 24 October, started to develop a rash that worsened in the following days.

Contacts of all three cases are being followed up by the UKHSA and other partner organisations and will be offered testing, vaccination and advice as needed.

Prof Susan Hopkins, chief medical adviser at UKHSA, said: “Mpox is very infectious in households with close contact and so it is not unexpected to see further cases within the same household.

“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 spreads between people through direct contact with rashes, skin lesions or scabs caused by the virus, including during sexual contact, kissing, cuddling or other skin-to-skin contact.

There is also a risk from contact with body fluids such as saliva or snot; contact with bedding or towels or clothing; and a possibility of spread through close and prolonged face-to-face contact such as talking, breathing, coughing or sneezing.

Symptoms include skin rash with blisters, spots or ulcers that can appear anywhere on the body, fever, headache, backache and muscle aches.

A rash usually appears one to five days after a fever, headache and other symptoms.

Clade Ib mpox has been widely circulating in the Democratic Republic of the Congo in recent months and there have been cases reported in Burundi, Rwanda, Uganda, Kenya, Sweden, India and Germany.

A report from the World Health Organization (WHO) and the Africa Centres for Disease Control and Prevention said there had been more than 40,000 mpox cases linked to almost 1,000 deaths in Africa as of the end of September 2024, with Clades Ia, Ib and II circulating in the region.

The WHO has declared a public health emergency of international concern because of the rapid spread of the mpox strain.

The health secretary, Wes Streeting, said last week that the government was working with UKHSA and the NHS “to protect the public and prevent transmission.

“This includes securing vaccines and equipping healthcare professionals with the guidance and tools they need to respond to cases safely.

“We are also working with our international partners to support affected countries to prevent further outbreaks,” he added.