The UK Health Security Agency (UKHSA) has confirmed a new case of  Clade Ib mpox, bringing the total to four cases, all within the same household.

The latest patient, currently receiving specialist care at Guy’s and St Thomas’ NHS Foundation Trust in London, has been isolating since identification as a contact of the initial case.

While health authorities emphasise that the risk to the general UK population remains low, the contagious nature of mpox within close-contact environments underscores the importance of monitoring and containment.

Mpox, a viral infection with symptoms such as fever, rash, muscle pain, and swollen lymph nodes, spreads through close contact with infected individuals, animals, or contaminated materials.

Clade Ib, the strain involved in these recent cases, is known to be more severe than Clade II, which circulated at lower levels in the UK over the past few years.

UKHSA has been closely tracking the spread of Clade Ib mpox since its emergence in Central Africa, particularly in the Democratic Republic of Congo, where it has been spreading within communities.

Other cases have also been reported in Europe and Asia, sparking global concern.

Professor Susan Hopkins, UKHSA’s Chief Medical Adviser, said: "Mpox is highly infectious within households with close contact, so it’s not unexpected to see further cases within the same household.

"However, the overall risk to the broader population is low. Our teams are working with partner organisations to ensure that all contacts are identified and appropriately managed to minimize further spread."

Following the initial diagnosis in late October, UKHSA activated its response protocols, deploying contact tracing and offering testing and vaccination to those exposed.

UKHSA has also assured that healthcare professionals across the country have been equipped and prepared for potential additional cases.

Contacts of the affected household have been offered preventive measures, including vaccines and symptom monitoring, to help prevent transmission.

With concerns rising over Clade Ib’s spread, the UK government has also taken steps to secure additional mpox vaccines and provide healthcare workers with guidance to safely handle potential cases.

Health and Social Care Secretary Wes Streeting reiterated that the risk to the public remains low, but he acknowledged the need for vigilance and readiness.

"We’re coordinating with international partners and monitoring developments closely," he said.