National case definition: Smallpox
Date of last revision/review: May 2008
Confirmed, probable and suspect cases of disease should be notified.
Contact the Public Health Agency of Canada immediately using the 24-hour emergency line 1-800-545-7661 even in the event of a suspected case.
Type of surveillance
Routine case-by-case notification to the federal level
Laboratory confirmation of infection:
- isolation of variola virus from an appropriate clinical specimen
- detection of variola virus nucleic acid
Clinical evidence of illness in a person who is epidemiologically linked to a laboratory-confirmed case or to a probable case
Laboratory evidence of infection:
- negative stain electron microscopic identification of variola virus in an appropriate clinical specimen
Clinical evidence of illness in a person who is not epidemiologically linked to a laboratory-confirmed case or to a probable case of smallpox
Atypical lesion known to be associated with the variola virus on a person who is epidemiologically linked to a laboratory-confirmed or probable case
Any testing related to suspected smallpox should be carried out under level 4 containment facilities at NML.
Contact the Public Health Agency of Canada immediately using the 24-hour emergency line (1-800-545-7661), even in the event of a suspected case, in order to activate the ERAP program.
Smallpox is characterized by a febrile prodrome consisting of fever > 38.3° C and systemic symptoms (prostration, headache, back pain, abdominal pain and/or vomiting), which generally lasts one to four days and is followed by the development of a characteristic rash. The rash consists of deep, firm, well-circumscribed pustules that are mostly all in the same stage of development. The lesions are characteristically umbilicated. The lesions initially appear as macules, evolving into papules, vesicles and then pustules in a matter of days. Finally, crusted scabs form; they then fall off several weeks after the initial appearance of the rash. Lesions initially appear in the oral mucosa/palate and then progress in a centrifugal pattern to involve the face, arms, legs, palms and soles. Atypical presentations include flat velvety lesions that do not evolve into pustules and more severe forms with confluent or hemorrhagic lesions.
- ICD-10 code(s): B03
- ICD-9 code(s): 050
Type of international reporting
Under the International Health Regulations (IHR) (2005), any event involving one or more cases of smallpox (as defined in WHO case definitionsFootnote 1) must be immediately notified to the World Health Organization (WHO), irrespective of the context in which they occur.
- Each State Party shall notify WHO by way of the IHR National Focal Point,Footnote 2 and within 24 hours of assessment of public health information, of all events which may constitute a public health emergency of international concern within its territory in accordance with the decision instrument (Annex 2 of the IHRFootnote 3), as well as any health measure implemented in response to those events.
- According to the algorithm in Annex 2 of the IHR, a case of smallpox is unusual or unexpected and may have serious public health impact and thus shall be notified to WHO.
It should be noted that the US Centers for Disease Control and Prevention (CDC), Emergency Preparedness and Response, provides slightly different case definitions. The CDC case definitions can be found at Enhanced Surveillance and Case Reporting.
Health Canada. Case definitions for diseases under national surveillance. CCDR 2000;26(S3). http://publications.gc.ca/collections/collection_2016/aspc-phac/HP3-1-26-S3-eng.pdf
Communicable Diseases Network Australia. Australian national notifiable diseases case definitions – Smallpox 2004:61. Retrieved July 2017 from http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-nndss-casedefs-cd_smpox.html
Damon I. Orthopoxviruses: vaccinia (smallpox vaccine), variola (smallpox), monkeypox and cowpox. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 6th ed. Vol 2. Philadelphia: Churchill Livingstone. Elsevier, 2006.
World Health Organization. International Health Regulations (2005). 3rd ed. Geneva, 2016, from http://www.who.int/ihr/publications/9789241580496/en/
- Footnote 1
WHO case definitions for the four diseases requiring notification in all circumstances under the IHR (2005). http://www.who.int/ihr/survellance_response/case_definitions/en/
- Footnote 2
In Canada, the IHR National Focal Point is located at the Public Health Agency of Canada.
- Footnote 3
IHR Annex 2 Decision Instrument is on pages 43-46 of the IHR Third Edition (2005): http://www.who.int/ihr/publications/9789241580496/en/
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