National case definition: Yellow fever

Date of last revision/review: May 2008

National notification

Only confirmed cases of disease should be notified.

Type of surveillance

Routine case-by-case notification to the federal level

Case classification

Confirmed case

Clinical illness with laboratory confirmation of infection:

• isolation of yellow fever virus

  or

• detection of yellow fever viral antigen in body fluids or tissue

  or

• detection of yellow fever nucleic acid in body fluids or tissue

  or

• a significant (i.e. fourfold or greater) rise in antibody titre to the yellow fever virus in the absence of yellow fever vaccination

  or

• a single elevated yellow fever IgM antibody titre in the absence of yellow fever vaccination within the previous two months

Probable case

Clinical illness with laboratory evidence of infection:

• a stable elevated antibody titre to yellow fever virus with no other known cause
• cross-reactive serologic reactions to other flaviviruses must be excluded, and the patient must not have a history of yellow fever vaccination

Clinical evidence

Yellow fever is a mosquito-borne viral illness characterized by acute onset of fever and constitutional symptoms followed by a brief remission and a recurrence of fever, hepatitis, albuminuria and, in some instances, renal failure, shock and generalized hemorrhages.

ICD code(s)

ICD-10 code(s): A95

• A95.0   Sylvatic yellow fever (Jungle yellow fever)
• A95.1   Urban yellow fever
• A95.9   Yellow fever, unspecified

ICD-9 code(s): 060

Type of international reporting

Under Article 6 of the International Health Regulations (IHR) (2005), each State Party shall notify the World Health Organization (WHO) by way of the IHR National Focal Point,^{Footnote 1}  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 IHR^{Footnote 2}), as well as any health measure implemented in response to those events.

• An event involving yellow fever shall always lead to the utilization of the algorithm in Annex 2 of the IHR, because it has demonstrated the ability to cause serious public health impact and to spread rapidly internationally. The need to notify such events to the WHO will depend upon the outcome of the assessment using the Annex 2 decision instrument.

Note: If event does not meet the criteria for notification under Article 6 of the IHR, then other IHR-related reporting requirements may still apply with WHO and/or other States Parties, including those under Art. 7 (information-sharing during unexpected or unusual public health events), Art. 8 (consultation with WHO on public health events), Art. 9 (any public health risk that may cause international disease spread), Art. 10 (requests for verification from WHO), and Art 44 (collaboration and assistance). 

Comments

Probable case definitions are provided as guidelines to assist with case finding and public health management, and are not for national notification purposes.