Case definition for surveillance of Zika virus infection

This case definition was published in Commission Implementing Decisions (EU) 2018/945 of 22 June 2018 on the communicable diseases and related special health issues to be covered by epidemiological surveillance as well as relevant case definitions.


Clinical criteria 

A person presenting with a rash.

Laboratory criteria

A. Confirmed case

At least one of the following:

  • Detection of Zika virus nucleic acid in a clinical specimen;
  • Detection of Zika virus antigen in a clinical specimen;
  • Isolation of Zika virus from a clinical specimen;
  • Detection of Zika virus specific IgM antibodies in serum sample(s) AND confirmation by neutralization test;
  • Seroconversion or four-fold increase in the titre of Zika specific antibodies in paired serum samples.

B. Probable case

Detection of Zika specific IgM antibodies in a serum sample.

Epidemiological criteria  

  • History of travel to, or residence in an area with documented on-going transmission of Zika virus, within the two-week period prior to the onset of symptoms


  • Sexual contact with a person recently exposed to or confirmed with Zika virus infection

Case Classification

A. Possible case: NA

B. Probable case

A person meeting the clinical and the epidemiological criteria, and the laboratory criteria for a probable case.

C. Confirmed case

A person meeting the laboratory criteria for a confirmed case.

Note: Serological results should be interpreted according to previous exposure to other flaviviral infections and the flavivirus vaccination status. Confirmed cases in such situations should be validated by serum neutralization assay or other equivalent assays.

Page last updated 29 Nov 2019