Case Definition

Clinical illness[1] with laboratory confirmation of infection: • Isolation of yellow fever virus from an appropriate clinical specimen OR • Detection of yellow fever antigen or nucleic acid (e.g., PCR) in an appropriate clinical specimen (e.g., body fluids or tissue)[2] OR • Seroconversion or significant (i.e., fourfold or greater) rise in HAI titre to the yellow fever virus in the absence of yellow fever vaccination OR • A single elevated yellow fever IgM[3] in the absence of yellow fever vaccination within the previous two months and in the absence of other elevated flavivirus titres. *The following probable case definition is provided as a guideline to assist with case finding and public health management, and should not be reported to AH. Probable Case* Clinical illness[1] with laboratory evidence of infection: • A stable elevated HAI titre to yellow fever virus with no other known cause AND • Cross-reactive serologic reactions to other flaviviruses has been excluded AND • The patient does not have a history of yellow fever vaccination. [1] Clinical Illness: a mosquito-borne viral illness characterized by acute onset and constitutional symptoms followed by a brief remission and recurrence of fever, hepatitis, albunimuria, and in some instances, renal failure, shock and generalized hemorrhages. [2] Refer to the National Microbiology Laboratory (NML) Guide to Services for current specimen collection and submission information. [3] Testing for yellow fever IgM is sent via the Provincial Laboratory of Public Health (ProvLab) to the Centers fo