Smallpox (Variola virus)

Clinical criteria
Any person with at least one of the following two:
- Fever
AND
Vesicles or firm pustules rash at the same stage of development with a centrifugal distribution
- Atypical presentations defined as at least one of the following four:
- Haemorrhagic lesions
- Flat velvety lesions not progressing to vesicles
- Variola sine eruptione
- Milder type

Laboratory criteria
- Laboratory criteria for case confirmation
At least one of the following two laboratory tests:

- Isolation of smallpox (variola virus) from a clinical specimen followed by sequencing (designated P4 laboratories only)
- Detection of variola virus nucleic acid in a clinical specimen followed by sequencing

Laboratory results need to be interpreted according to the vaccination status
- Laboratory criteria for a probable case

- Identification of orthopox virus particles by EM

Epidemiological criteria
At least one of the following two epidemiological links:
- Human to human transmission
- Laboratory exposure (where there is a potential exposure to variola virus)

Case classification
A. Possible case
Any person meeting the clinical criteria
B. Probable case
Any person meeting the clinical criteria and with at least one of the following two:
- An epidemiological link to a confirmed human case by human to human transmission
- Meeting the laboratory criteria for a probable case
C. Confirmed case
Any person meeting the laboratory criteria for case confirmation.
During an outbreak: any person meeting the clinical criteria and with an epidemiological link.

Current as of: 24 January 2019