This guidance describes case definitions to inform testing and reporting of suspected mpox 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.
A possible case is defined as anyone who fits one or more of the following criteria:
- a febrile prodrome† compatible with mpox 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 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).
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 mpox 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 for 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 Central Africa in the 21 days before symptom onset please discuss with the imported fever service, as these patients may need to be managed as having an HCID. 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 where mpox remains the most likely diagnosis.
A confirmed case is defined as a person with a laboratory-confirmed mpox infection (MPXV PCR positive).
Actions for 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 mpox.
All confirmed or highly probable cases should be notified to the local health protection team by the clinician.