Monkeypox:Mpox (monkeypox): case definitions

This guidance describes case definitions to inform testing and reporting of suspected monkeypoxmpox cases.

This document provides the case definitions for mpox, the disease caused by the monkeypox virus. Further information on the high consequence infectious disease (HCID) status of mpox is available.

Possible case

A possible case is defined as anyone who fits one or more of the following criteria:

  • a febrile prodrome compatible with monkeypoxmpox infection, where there is known prior contact with a confirmed case in the 21 days before symptom onset
  • an illness where the clinician has a suspicion of monkeypox,mpox, such as unexplained lesions, including but not limited to:
    • genital, ano-genital or oral lesion(s) – for example, ulcers, nodules
    • proctitis – for example anorectal pain, bleeding

Febrile prodrome consists of fever ≥ 38°C, chills, headache, exhaustion, muscle aches (myalgia), joint pain (arthralgia), backache, and swollen lymph nodes (lymphadenopathy).

Probable case

A probable case is defined as anyone with an unexplained rash or lesion(s) on any part of their body (including genital/perianal, oral), or proctitis (for example anorectal pain, bleeding) and who:

  • has an epidemiological link to a confirmed, probable or highly probable case of monkeypoxmpox in the 21 days before symptom onset


  • identifies as a gay, bisexual or other man who has sex with men (GBMSM)


  • has had one or more new sexual partners in the 21 days before symptom onset

Actions onfor a possible or probable case

Test for monkeypox virus (MPXV), the causative agent of mpox (using designated testing pathway).

Take travel history: if patient reports a travel history to West or Central Africa in the 21 days before symptom onset please discuss with the Importedimported Feverfever Service,service, as these patients may need to be managed as having aan highHCID. consequence infectious disease. Undertake additional contemporaneous tests to rule out alternative diagnoses if clinically appropriate and if not done already.

If admission of patient required for clinical reasons, admit to single room isolation at negative or neutral pressure at local hospital site with respiratory protective equipment (RPE) and personal protective equipment (PPE) (with appropriate IPC arrangements).

Or, if patient not requiring admission for clinical reasons: self-isolation at home (based on assessment by the clinician and following UKHSA guidance).

Or, if patient not requiring admission for clinical reasons but self-isolation at home is not possible for social or medical reasons following clinician assessment: isolation in single room at negative or neutral pressure at local hospital site with RPE and PPE pending test result (prioritise probable cases).

Highly probable case

A highly probable case is defined as a person with an orthopox virus PCR positive result in 2022 and where monkeypoxmpox remains the most likely diagnosis.

Confirmed case

A confirmed case is defined as a person with a laboratory-confirmed monkeypoxmpox infection (monkeypox(MPXV PCR positive) in 2022.positive).

ActionActions onfor a confirmed or highly probable case

All confirmed or highly probable cases should be assessed for the need for admission based on either clinical or self-isolation requirements. The NHS provides guidance on management of patients with confirmed monkeypoxmpox.

All confirmed or highly probable cases should be notified to the local health protection team by the clinician.

Further information

Additional monkeypoxmpox resources are available on GOV.UK, including guidance on vaccination and contact tracing.

Published 20 May 2022
Last updated 923 AugustJanuary 20222023 + show all updates
  1. Updated in line with the HCID derogation of Clade II mpox.

  2. Updated actions on a possible or probable case.

  3. Added highly probable case definition, and amended actions for confirmed or highly probable cases. Updated possible and probable case definitions.

  4. Removed requirement to notify HCID network about all confirmed cases. Added link to NHS pages on management.

  5. Updated actions for confirmed cases.

  6. Updated probable case information.

  7. Added links to additional monkeypox guidance.

  8. First published.