UKHSA detects first case of Clade Ib mpox

The UK Health Security Agency (UKHSA) has detected a single confirmed human case of Clade Ib mpox. The risk to the UK population remains low.

This is the first detection of this Clade of mpox in the UK. It is different from mpox Clade II that has been circulating at low levels in the UK since 2022, primarily among gay, bisexual and other men-who-have-sex-with-men (GBMSM).

UKHSA, the NHS and partner organisations have well tested capabilities to detect, contain and treat novel infectious diseases, and while this is the first confirmed case of mpox Clade Ib in the UK, there has been extensive planning underway to ensure healthcare professionals are equipped and prepared to respond to any confirmed cases.

The case was detected in London and the individual has been transferred to the Royal Free Hospital High Consequence Infectious Diseases unit. They had recently travelled to countries in Africa that are seeing community cases of Clade Ib mpox. The UKHSA and NHS will not be disclosing any further details about the individual.

Close contacts of the case are being followed up by UKHSA and partner organisations. Any contacts will be offered testing and vaccination as needed and advised on any necessary further care if they have symptoms or test positive.

UKHSA is working closely with the NHS and academic partners to determine the characteristics of the pathogen and further assess the risk to human health. While the existing evidence suggests mpox Clade Ib causes more severe disease than Clade II, we will continue to monitor and learn more about the severity, transmission and control measures. We will initially manage Clade Ib as a high consequence infectious disease (HCID) whilst we are learning more about the virus.

Professor Susan Hopkins, Chief Medical Adviser at UKHSA, said:

It is thanks to our surveillance that we have been able to detect this virus. This is the first time we have detected this Clade of mpox in the UK, though other cases have been confirmed abroad.

The risk to the UK population remains low, and we are working rapidly to trace close contacts and reduce the risk of any potential spread. In accordance with established protocols, investigations are underway to learn how the individual acquired the infection and to assess whether there are any further associated cases.

Health and Social Care Secretary Wes Streeting, said:

I am extremely grateful to the healthcare professionals who are carrying out incredible work to support and care for the patient affected.

The overall risk to the UK population currently remains low and the government is working alongside 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.

Steve Russell, NHS national director for vaccination and screening, said:

The NHS is fully prepared to respond to the first confirmed case of this clade of mpox.

Since mpox first became present in England, local services have pulled out all the stops to vaccinate those eligible, with tens of thousands in priority groups having already come forward to get protected, and while the risk of catching mpox in the UK remains low, if required the NHS has plans in place to expand the roll out of vaccines quickly in line with supply.

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

Clade Ib mpox was detected by UKHSA using polymerase chain reaction (PCR) testing.

Common symptoms of mpox include a skin rash or pus-filled lesions which can last 2 to 4 weeks. It can also cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes.

The infection can be passed on through close person-to-person contact with someone who has the infection or with infected animals and through contact with contaminated materials. Anyone with symptoms should continue to avoid contact with other people while symptoms persist.

The UK has an existing stock of mpox vaccines and last month announced further vaccines are being procured to support a routine immunisation programme to provide additional resilience in the UK. This is in line with more recent independent JCVI advice.

Working alongside international partners, UKHSA has been monitoring Clade Ib mpox closely since the outbreak in DRC first emerged, publishing regular risk assessment updates.

The wider risk to the UK population remains low.

UKHSA has published its first technical briefing on clade I mpox which provides further information on the current situation and UK preparedness and response.