Monkeypox: case definitions

Possible case

A personpossible withcase is defined as anyone who fits one or more of the following criteria:

• a febrile prodrome^† compatible with monkeypox infection where there is known prior contact with a confirmed case in the 21 days before symptom onset.

  Or, a person with onset

• an illness where the clinician has a high suspicion of monkeypox (for– example, this maycould include prodromeunexplained orgenital, atypicalano-genital presentationsor withoral exposurelesion(s) histories(for deemedexample, highulcers, risknodules) by the clinician, or classicalproctitis rash(for withoutexample riskanorectal factors).
  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 personprobable case is defined as anyone with an unexplained rash or lesion(s) on any part of their body plus(including onegenital/perianal, ororal), more classical symptom or symptomsproctitis of(for monkeypoxexample infection^¥anorectal sincepain, 15bleeding) March 2022 and either:who:

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

or

• reportedidentifies as a travelgay, historybisexual to West or Centralother Africaman inwho thehas 21sex dayswith beforemen symptom onset(GBMSM)

or

• ishas ahad gay,one bisexual or othermore mannew whosexual haspartners sexin withthe men21 (GBMSM)days before symptom onset

^¥Acuteor

• reports illnessa withtravel feverhistory (>38.5°C),to intenseWest headaches,or myalgia,Central arthralgia,Africa backin pain,the lymphadenopathy.
  21 days before symptom onset

Actions on a possible or probable case

Test for monkeypox (using designated testing pathway).pathway).

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 RPE 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 PPE pending test result (prioritise probable cases).

Highly probable case

A highly probable case is defined as a person with an orthopox virus positive result since 15 March 2022 and where monkeypox remains the most likely diagnosis.

Confirmed case

A confirmed case is defined as a person with a laboratory confirmed monkeypox infection (monkeypox PCR positive).

Action on 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 monkeypox.

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

Further information

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