Criteria

World Health Organization: case definitions for public health surveillance (2015)[40]

Suspected case

  • Any person with acute onset of fever, with jaundice appearing within 14 days of onset of the first symptoms.

Probable case

A suspected case; and one of the following:

  • Presence of yellow fever IgM antibody in the absence of yellow fever immunization within 30 days before onset of illness; or

  • Positive post mortem liver histopathology; or

  • Epidemiologic link to a confirmed case or an outbreak.

Confirmed case

A probable case and either:

  • Absence of yellow fever immunization within 30 days before onset of illness, and one of the following:

    • Detection of yellow fever-specific* IgM; or

    • Detection of fourfold increase in yellow fever IgM, or IgG antibody titers between acute and convalescent serum samples, or both; or

    • Detection of yellow fever-specific* neutralizing antibodies.

  • Absence of yellow fever immunization within 14 days before onset of illness, and one of the following:

    • Detection of yellow fever virus genome in blood or other organs by PCR; or

    • Detection of yellow fever antigen in blood, liver, or other organs by immunoassay; or

    • Isolation of yellow fever virus.

* "Yellow fever-specific" means that the results of antibody tests (e.g., IgM or neutralizing antibody) for other prevalent flaviviruses are negative or not significant. Testing should include at least IgM for dengue fever and West Nile virus, but may include other flaviviruses according to local epidemiology (e.g., Zika virus).

Centers for Disease Control and Prevention: 2019 case definition[38]

Clinical criteria

A clinically compatible case is defined as:

  • Acute illness with at least one of the following: fever, jaundice, or elevated total bilirubin ≥3 mg/dL; and

  • Absence of a more likely clinical explanation.

Probable case

A clinically and epidemiologically compatible case with:

  • Yellow fever virus-specific IgM antibodies in cerebrospinal fluid (CSF) or serum; and

  • Negative IgM results for other arboviruses endemic to the region where exposure occurred; and

  • No history of yellow fever vaccination.

Confirmed case

A clinically compatible case that meets one or more of the following criteria:

  • Isolation of yellow fever virus from, or demonstration of yellow fever viral antigen or nucleic acid in, tissue, blood, CSF, or other body fluid, and no history of yellow fever vaccination within 30 days of illness onset, unless there is molecular evidence of infection with wild-type yellow fever virus

  • Four-fold or greater rise, or fall, in yellow fever virus-specific neutralizing antibody titers in paired sera, and no history of yellow fever vaccination within 30 days of illness onset

  • Yellow fever virus-specific IgM antibodies in CSF or serum with confirmatory virus-specific neutralizing antibodies in the same or a later specimen, and no history of yellow fever vaccination.

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