#18,380
Starting in 2018, the UK began to treat all MPXV infections as a High Consequence infectious disease (HCID), which they defined as:
- an acute infectious disease
- typically having a high case-fatality rate
- not always having effective prophylaxis or treatment
- often difficult to recognise and detect rapidly
- able to spread in the community and within healthcare settings
- requiring an enhanced individual, population and system response to ensure it is managed effectively, efficiently and safely
Clade I Mpox viruses, however - due to reports of more serious illness and higher case fatality rates in Central Africa - remained classified as HCIDs.
The UK has now reported 10 clade I cases (7 travel-related, 3 locally acquired), and based on that experience they have decided that Mpox Clade I cases will no longer be treated as HCIDs. Some excerpts from that announcement follow:
Guidance
Derogation of clade I mpox
Urgent public health message advising that clade I mpox no longer meets the criteria of a high consequence infectious disease (HCID).
From: UK Health Security Agency Published19 March 2025
The Advisory Committee on Dangerous Pathogens (ACDP) recently assessed evidence gathered by UKHSA for clade I mpox and advised that it no longer met the criteria of a high consequence infectious disease (HCID). Therefore, the Chief Medical Officers (CMOs) of the 4 nations have agreed that mpox will no longer be managed as an HCID within healthcare settings.
Mpox remains a serious infection for some individuals and remains a World Health Organization (WHO) public health emergency of international concern (PHEIC). The UK’s strategic goal continues to be to eliminate person-to-person transmission of mpox in the UK. Therefore, there will be ongoing public health management of cases and contacts, including vaccination where appropriate.
Actions for the NHS
1. Providers should be aware that all mpox (clade I and clade II) is no longer classed as an HCID.
2. Providers should ensure that relevant clinical services – including primary care, urgent care, sexual health services, paediatrics, obstetrics, and emergency departments (EDs) - are aware of the information in this public health message, and that a differential diagnosis of mpox infection (caused by the virus MPXV) is considered wherever appropriate.
3. Providers should ensure that they have adequate stocks of appropriate personal protective equipment (PPE) for use during the assessment and treatment of patients presenting with suspected mpox, and for use by cleaners of rooms or areas where suspected or confirmed cases have been. Staff must be trained on the safe removal of PPE to avoid self-contamination.
4. Providers should ensure there is a clinical pathway for appropriate isolation and management of suspected mpox cases within their setting, incorporating the information provided in this alert and their relevant country’s national infection prevention manual. This should include:
- isolation of the patient
- liaison with local infection prevention and control (IPC) teams
- arrangements for discussion of the case with local infectious disease, microbiology or virology consultants
- thorough cleaning and decontamination of rooms or areas where the suspected case has been
5. Registered medical practitioners are reminded that mpox is an urgent notifiable disease. They should ensure that suspected mpox cases are notified to their local health protection team so that appropriate public health measures, including contact identification and management can be considered.
Find out about notification in each nation:
6. Integrated Care Boards (ICBs) and commissioners (where this is relevant in the UK) should ensure there are effective pathways in place for post-exposure prophylaxis for high-risk contacts of cases, and ring vaccination where necessary.
7. Providers should ensure there are effective vaccination pathways in place to deliver pre-exposure prophylaxis to staff identified in higher risk occupational groups as set out in the Mpox outbreak: vaccination strategy.
8. Samples from individuals testing positive for MPXV must be sent for clade differentiation as part of ongoing surveillance and management of risk to the UK from mpox. In England, this is available from the UKHSA Rare and Imported Pathogens Laboratory (RIPL). In the devolved administrations, clade testing is available at the National Laboratories. If clade testing is available locally, laboratories should ensure that the assays are up to date and able to differentiate clades Ia, Ib and II, and that reporting pathways are updated so that clade information is captured through the Second Generation Surveillance System (SGSS).
