Yellow fever (YF) is a viral haemorrhagic fever. It is transmitted by mosquitos infected with the YF virus. The disease is untreatable and case-fatality rates can exceed 50% among severe cases. YF can be prevented through immunization with the 17D YF vaccine, which is safe, inexpensive and reliable. A single dose provides protection against the disease for at least 10 years and possibly throughout life.

A high risk exists of an explosive outbreak in an unimmunized population even if there is only one laboratory-confirmed case in the population. Children are especially vulnerable. Effective disease surveillance activities remain the best tool for prompt detection of and response to outbreaks, particularly in populations where coverage rates for YF vaccine are not high enough to provide protection.

Each country at risk should include YF surveillance in its national priorities for disease surveillance. Current capacity for YF surveillance should be assessed and a plan of action for establishing or strengthening it should be implemented. The minimum requirements for a YF surveillance system are detection, investigation, specimen collection and a reporting system for suspected cases, linked to confirmatory testing of samples.

All countries at risk should have access to a qualified laboratory capable of confirming YF by an IgM test. All countries should be aware of the regional reference laboratories that can aid them in confirmatory testing. Procedures for transporting specimens between laboratories and for testing the specimens should be formally established.