Clade I mpox virus infection
Urgent public health message to all NHS service providers regarding Clade I mpox virus (MPXV) infection.
Actions for the NHS
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Providers to ensure that relevant clinical services – including primary care, urgent care, sexual health services, paediatrics, obstetrics and emergency departments – are aware of the information in this public health message and that a differential diagnosis of Clade I mpox virus (MPXV) infection is considered in any patient who meets the operational case definition below.
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Providers to ensure that they have adequate stocks of appropriate personal protective equipment (PPE) and relevant staff are trained in its use for the assessment and treatment of patients presenting with suspected Clade I MPXV infection.
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Providers to ensure there is a clinical pathway for isolation and management of suspected Clade I MPXV cases within their setting. This should include isolation of the patient, liaison with local infection prevention and control (IPC) teams, and arrangements for discussion of the case with local infectious disease, microbiology or virology consultants if a diagnosis of Clade I MPXV is being considered so that appropriate clinical management, including testing and infection control measures, can be implemented.
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All samples from all individuals testing positive for mpox must be sent to the UKHSA Rare and Imported Pathogens Laboratory (RIPL) for clade differentiating tests.
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Providers to note the information below for the clinical assessment and testing of patients with potential Clade I MPXV infection.
Background
MPXV is a virus from the same family as smallpox, that presents with a rash illness which may be mild and localised, or severe and disseminated. There are 2 distinct clades of the virus: Clade I and Clade II. Clade II MPXV is responsible for the global outbreak that began in 2022. Clade I MPXV is currently considered more severe than Clade II MPXV, leading to its classification as a high consequence infectious disease (HCID).
Historically, Clade I MPXV has been reported only in 5 Central African countries. However, recent cases in additional countries within Central and East Africa mark the first known expansion of its geographical range, heightening the risk of spread beyond the region. Evidence of sustained sexual transmission of Clade I MPXV has emerged in the Democratic Republic of Congo (DRC). Healthcare professionals should remain vigilant for Clade I MPXV, including in sexually acquired mpox cases, and should obtain comprehensive travel histories from patients.
The symptoms of mpox begin 5 to 21 days (average 6 to 16 days) after exposure with initial clinical presentation of fever, malaise, lymphadenopathy and headache. Within 1 to 5 days after the appearance of fever, a rash develops, often beginning on the face or genital area and it may then spread to other parts of the body. The rash changes and goes through different stages before finally forming a scab which later falls off. Treatment for MPXV is mainly supportive.
Clinical assessment and operational mpox HCID case definition
The following patients should be managed as HCID cases (pending confirmation of clade type where appropriate):
- confirmed mpox where Clade I MPXV has been confirmed
- confirmed or clinically suspected mpox, clade not yet known and:
- there is a travel history to the DRC or specified countries where there may be a risk of Clade I exposure
- or a link to a suspected case from those countries (listed below), within 21 days of symptom onset
- or there is an epidemiological link to a case of Clade I mpox within 21 days of symptom onset
The countries where Clade I cases have been reported, as well as countries bordering those with ongoing Clade I transmission are currently:
- DRC
- Republic of Congo
- Central African Republic
- Burundi
- Rwanda
- Uganda
- Kenya
- Cameroon
- Gabon
- Angola
- South Sudan
- Tanzania
- Zambia
Given the rapid spread of Clade I in the African region, please check the UKHSA mpox pages regularly for any updates to the countries included.
Mpox is not considered an HCID in the following circumstances:
- a case has a laboratory confirmed Clade II mpox virus (MPXV) infection
Or:
- a confirmed or clinically suspected mpox case of an unknown clade and none of the epidemiological characteristics listed above in the operational HCID case definition apply
Management of possible cases
Clinicians should be alert to the possibility of Clade I MPXV infection in patients presenting with suspected mpox where there is a link to the specified countries in the African region (as listed above). Clinicians treating patients with suspected mpox who may meet the operational case definition of an HCID (as outlined above) should discuss this with local infection specialists.
Infection Specialists should discuss all possible Clade I MPXV cases with the UKHSA Imported Fever Service (IFS) on 0844 778 8990 so that testing can be expedited. Patients with severe disease (who do not meet the operational case definition) should also be discussed with the IFS.
Individuals with clinically suspected mpox presenting to acute care settings who meet the case definition for possible Clade I MPXV infection should be isolated and managed as a HCID as outlined in the National Infection Prevention and Control Manual.
In outpatient settings, individuals presenting with clinically suspected mpox who meet the case definition for possible Clade I MPXV infection should be isolated appropriately (single room, closed door) and clinical staff should wear fluid resistant surgical face masks (FRSM) or face fit tested FFP3 masks, eye protection, long-sleeved splash resistant gowns or apron and gloves to provide care if immediately required.
Where suspected cases meeting the operational case definition present in primary care, General Practitioners should isolate the patient in a side room and contact their local infection service for advice, including appropriate arrangements for transfer into secondary care and immediate precautions in the setting.
All samples from all individuals testing positive for MPXV (regardless of whether there are potential links to Clade I or travel from the African region) must be sent to the UKHSA RIPL for clade differentiating tests. UKHSA will contact Trusts for samples for any mpox cases for which samples have not been received for clade typing.
Cases of confirmed Clade I MPXV infection will be managed through the specialist network of HCID centres.
UKHSA’s mpox resource collection will be kept up to date with information on affected areas for the duration of the outbreak to assist NHS clinicians in diagnosis.