Mpox: guidance on when to suspect a case of mpox
This guidance describes symptoms of mpox and epidemiological criteria to help inform testing and reporting of suspected cases.
This guidance is for healthcare professionals on when to suspect mpox, the disease caused by any clade of the virus called MPXV, and how to decide if a suspected case needs to be managed as a High Consequence Infectious Disease (HCID). Clade II mpox has been circulating in the UK and globally since 2022 predominantly in gay, bisexual or other men who have sex with men, but remains uncommon. It is no longer classified as an HCID.
Clade I mpox is currently classified as an HCID. It includes clade Ia, present in central Africa, and clade Ib, currently causing an outbreak in multiple countries (see the affected country list).
Consider the possibility of mpox when patients with exposure risk and which fit the clinical description in the section on When to suspect mpox. When assessing patients for mpox, always consider the possibility of HCID and take a travel history. If the patient fits the HCID case definition, they should be managed as potential HCID and discussed with local infection team, who may refer to the Imported Fever Service.
When to suspect mpox
Consider mpox where a case presents with:
1. a prodrome (fever, chills, headache, exhaustion, myalgia, arthralgia, backache, lymphadenopathy), and where there is known prior contact with a confirmed or suspected case of mpox in the 21 days before symptom onset
Or:
2. an mpox-compatible rash anywhere on the skin (face, limbs, extremities, torso), mucosae (including oral, genital, anal), or symptoms of proctitis, and at least one of the following in the 21 days before symptom onset:
- recent new sexual partner
- contact with known or suspected case of mpox
- a travel history to a country where mpox is currently common
- link to an infected animal or meat
If the rash is highly clinically suggestive of mpox, but you cannot identify a risk factor, discuss with local infection services whether to consider mpox testing alongside the more common differential diagnosis.
Consider common infections such as chickenpox or shingles, herpes simplex virus, and enterovirus in the differential diagnosis; these circulate widely and are more common than mpox; exclude as appropriate.
When to consider clade I mpox, a high consequence infectious disease (HCID operational case definition)
In a person with clinically suspected mpox, they should be managed as HCID if they meet one or more of the following criteria:
- has a travel history to specified countries where there may be a risk of clade I exposure in the 21 days before symptom onset (see affected country list)
- has an epidemiological link to a confirmed or suspected case of clade I mpox in the 21 days before symptom onset
- has a relevant zoonotic link, including contact with a wild or captive mammal that is an African native species (this includes contact with derived products, for example, game meat)
Actions for a suspected case of mpox
For all suspected mpox cases
Patients identified as suspected mpox cases should be managed as per the NHS guidance on Infection prevention and control measures for clinically suspected and confirmed cases of mpox in healthcare settings.
All suspected cases undergoing testing should be notified to the local health protection team by the clinician.
For cases meeting the HCID mpox case definition
The managing clinician should contact their relevant local infection team (infectious diseases, microbiology, or virology). The local infection team should then discuss with the IFS (0844 778 8990) who will review risk assessment and advise on the next steps for investigation and management including the need for admission. If a decision is made to test, information on diagnostic testing for mpox is available. The managing clinician should contact the local health protection team.
For cases that do not meet the HCID mpox case definition
Test for MPXV, the causative agent of mpox (using designated testing pathway). See also Mpox diagnostic testing guidance.
Undertake tests to rule out alternative diagnoses if clinically appropriate and if not done already.
If patient requires admission for clinical reasons, IPC measures should be undertaken as per the NHS guidance on IPC measures for clinically suspected and confirmed cases of mpox in healthcare settings and the national IPC manual.
If patient does not require admission for clinical reasons: advise self-isolation at home (based on assessment by the clinician and following UKHSA guidance). If the patient cannot self-isolate at home, the patient should be admitted pending test result, with IPC measures undertaken as per the NHS guidance on IPC measures for clinically suspected and confirmed cases of mpox in healthcare settings and the national IPC manual.
Case definitions once test results are available
Highly probable case
A highly probable case is defined as a person with an orthopox virus PCR positive result where mpox remains the most likely diagnosis.
Confirmed case
A confirmed case is defined as a person with a laboratory-confirmed mpox infection (MPXV PCR positive).
Further information
Additional mpox resources are available on GOV.UK, including guidance on vaccination and contact tracing.
Updates to this page
Last updated 31 October 2024 + show all updates
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Minor update to reflect the first detection of clade I mpox in the UK.
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Added information on when to consider clade I (HCID) mpox, and updated information on when to suspect mpox and actions for a suspected case
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Updated links to direct to the NHS guidance on IPC measures for mpox cases in healthcare settings, and to the Green Book chapter 29.
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Probable and possible case definitions combined into one suspected case definition. Added actions for those managing a suspected case of HCID mpox.
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Updated to include HCID mpox (Clade I) and link to operational HCID definition.
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Updated in line with the HCID derogation of Clade II mpox.
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Updated actions on a possible or probable case.
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Added highly probable case definition, and amended actions for confirmed or highly probable cases. Updated possible and probable case definitions.
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Removed requirement to notify HCID network about all confirmed cases. Added link to NHS pages on management.
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Updated actions for confirmed cases.
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Updated probable case information.
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Added links to additional monkeypox guidance.
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First published.