National case definition: Mpox
Date of last revision/review: April 2025
On this page
- National notification
- Type of surveillance
- Surveillance case definitions for mpox in Canada
- ICD codes
National notification
Probable and confirmed cases of disease should be notified
Type of surveillance
Routine case-by-case notification to the federal level
Surveillance case definitions for mpox in Canada
Suspected case
A person of any age who presents with one or more of the following:
- An unexplainedFootnote 1 acute skin rash or lesion(s)Footnote 2 AND has at least one of the following signs or symptoms
- Headache
- Acute onset of fever (>38.5°C)
- Lymphadenopathy (swollen lymph nodes)
- Myalgia (muscle and body aches)
- Back pain
- Prostration/asthenia (profound weakness)
- Fatigue
- Pharyngitis (sore throat)
- Proctitis (rectal inflammation/pain)
- An unexplainedFootnote 1 acute genital, perianal, anorectal and/or perioral, oral, or oropharyngeal rash or lesion(s)Footnote 2
Probable case
A person of any age who meets the suspect case definition
and
Has one or more of the following:
- Has an epidemiological link to a probable or confirmed mpox case in the 21 days before symptom onset
- Has an epidemiological link to a location/event where transmission of mpox is suspected or known to have occurred in the 21 days before symptom onset
An epidemiological link can be:
- Face-to-face exposure, including health workers without appropriate personal protective equipment (PPE)
- Direct physical contact, including sexual contact; or contact with contaminated materials such as clothing or bedding
Confirmed case
A person who is laboratory confirmed for mpox virus (MXPV) by detection of unique sequences of viral DNA either by real-time polymerase chain reaction (PCR) and/or sequencing
Reinfection case
A person of any age who has a documented history of a previous episode of mpox, as a confirmed caseFootnote 3
and
- Has a subsequent laboratory-confirmed MPXV infection by detection of unique sequences of viral DNA either by real-time PCR and/or sequencing with clinical evidence of reinfectionFootnote 3 :
- Full clinical resolutionFootnote 4 of the previous mpox episode occurred and the time between the resolution of the first episode and the onset of new symptoms is three months or more
or
- Has a subsequent laboratory-confirmed MPXV infectionFootnote 3 by detection of unique sequences of viral DNA either by real-time PCR and/or sequencing with laboratory evidence of reinfection:
- Genome sequencing indicates substantial single nucleotide polymorphisms (SNPs) or significant strain differentiation between the two MPXV infections
ICD code(s)
- ICD-11 codes : XN4L3 Monkeypox virus clade I
- XN9XX Monkeypox virus Clade Ia
- XN8ZK Monkeypox virus Clade Ib
- XN1BH Monkeypox virus Clade II
- XN00B Monkeypox virus Clade IIa
- XN7VR Monkeypox virus Clade IIb
- ICD-10 code: B04
Footnotes
- Footnote 1
-
Common infectious causes of acute rash or lesion(s) can include varicella, shingles, measles, herpes simplex, syphilis, chancroid, lymphogranuloma venereum, hand-foot-and-mouth disease.
N.B. It is not necessary to obtain negative laboratory results for other possible infectious causes of rash or lesion(s) listed in order to classify a case as suspected.
- Footnote 2
-
Acute rash or lesion(s)
Mpox illness includes a rash or lesion(s) that can affect the mucous membranes in the oropharynx and anogenital area. The rash or lesion(s) can also affect the face, trunk, limbs, and palms of hands and soles of the feet. The rash or lesion(s) can last for 2 to 4 weeks and may appear as singular or multiple macules, pustules, vesicles, crusted lesions or ulcers. Lesions in varying stages can be present simultaneously. Anorectal lesions can manifest as anorectal inflammation (proctitis), pain and/or bleeding.
- Footnote 3
-
Considerations for differentiating reinfection from persistence in people who are immunocompromised: Mpox disease progression may differ in individuals who are immunocompromised. Individuals who are immunocompromised include individuals with immunodeficiencies, those with active cancer, transplant recipients, individuals receiving treatment with immunosuppressive agents. They also include people living with human immunodeficiency virus with a current CD4 cell count of <200 cells/µl. These immunocompromised individuals may experience prolonged viral persistence and varied clinical manifestations due to impaired viral clearance. If MPXV DNA sequencing is not available for either the initial or reinfection, an individualized reinfection case classification is appropriate, considering immune status, clinical presentation, and epidemiological risk factors, to accurately distinguish between reinfection or recrudescence.
- Footnote 4
-
Full clinical resolution is defined as the disappearance of all clinical symptoms of mpox e.g., fever, lymphadenopathy, skin rashes or lesions caused by MPXV, and any other persistent symptoms associated with the previous MPXV (acute) infection, except for the long-term sequalae.
References
- Barnes AH, Smith C, Dash A, Shishido AA et al. Mpox: Special Considerations in the Immunocompromised Host. Curr Treat Options Infect Dis. 2022; 14:43–66. https://doi.org/10.1007/s40506-022-00260-5.
- Centers for Disease Control and Prevention. Monkeypox Virus Infection 2022 Case Definition. Updated February 28, 2023. https://ndc.services.cdc.gov/case-definitions/monkeypox-virus-infection-2022/. Accessed May 22, 2024.
- Hazra A, Zucker J, Bell E, et al.; SHARE-NET writing group. Mpox in people with past infection or a complete vaccination course: a global case series. Lancet Infect Dis. 2024 Jan;24(1):57-64. doi: 10.1016/S1473-3099(23)00492-9.
- Suñer C, Ubals M, Tarín-Vicente EJ, et al. Viral dynamics in patients with monkeypox infection: a prospective cohort study in Spain. Lancet Infect Dis. 2023 Apr;23(4):445-453. doi: 10.1016/S1473-3099(22)00794-0.
- World Health Organization. Surveillance, case investigation and contact tracing for mpox (monkeypox): Interim Guidance 20 March 2024. https://www.who.int/publications/i/item/B09169. Accessed May 22, 2024.