Criteria

World Health Organization (WHO): interim case definition

An interim case definition has been published by the WHO for the purpose of global standardisation of classification and reporting.[171]

Suspected case:

  • A person presenting with rash and/or fever and at least one of the following signs or symptoms:

    • Arthralgia

    • Arthritis

    • Conjunctivitis (non-purulent/hyperaemic).

Probable case:

  • A suspected case with the presence of IgM antibodies against Zika virus and no evidence of infection with other flaviviruses, plus an epidemiological link (i.e., contact with a confirmed case, or a history of residence in or travelling to an area with local transmission of Zika virus within 2 weeks prior to onset of symptoms).

Confirmed case:

  • A person with laboratory confirmation of recent Zika virus infection:

    • Presence of Zika virus RNA or antigen in serum or other samples (e.g., saliva, tissues, urine, whole blood)

    • IgM antibody against Zika virus is positive and plaque reduction neutralisation test (PRNT) for Zika virus with titre ≥20 and Zika virus PRNT titre ratio ≥4 compared with other flaviviruses.

WHO: Zika virus disease - interim case definition

Pan American Health Organization (PAHO): interim Zika virus case definition

An interim case definition has been published by the PAHO.[150]

Suspected case:

  • Patient with rash (usually pruritic and maculopapular) plus 2 or more of the following:

    • Fever (usually <38.5°C [<101.3°F])

    • Conjunctivitis (non-purulent/hyperaemic)

    • Arthralgia

    • Myalgia

    • Peri-articular oedema.

  • In geographical areas without autochthonous transmission and where there are no vectors present, patients who meet the criteria above and who:

    • in the 2 weeks prior to onset, travelled to/resided in a geographical area where there is known local transmission of the Zika virus or there is known vector presence; or

    • had unprotected sex in the 2 weeks prior to onset with a person who travelled in the previous 8 weeks to a geographical area with known local transmission of the Zika virus or an area with known vector presence.

Probable case:

  • Patient who meets the criteria of a suspected case and has Zika IgM antibodies with no evidence of infection with other flaviviruses.

Confirmed case:

  • Patient who meets the criteria of a suspected case and has laboratory confirmation of recent Zika virus infection:

    • RNA or Zika virus antigen in any specimen (i.e., serum, urine, saliva, tissue, or whole blood); or

    • Positive Zika IgM antibodies and PRNT for Zika virus titres ≥20 and 4 or more times greater than the titres for other flaviviruses, as well as exclusion of other flaviruses; or

    • Detection of viral genome (in fresh or paraffin tissue) in autopsy specimens by molecular techniques, or detection by immunochemistry.

PAHO have also published case definitions for Guillain-Barre syndrome or a congenital syndrome associated with Zika virus, as well as definitions for Zika virus-associated abortion or still birth and vertical transmission (without congenital syndrome).

Pan American Health Organization: case definitions

Centers for Disease Control and Prevention (CDC): arboviral diseases case definition

The CDC includes Zika virus infection in their arboviral diseases (neuroinvasive and non-neuroinvasive) case definition:

CDC: arboviral diseases, neuroinvasive and non-neuroinvasive 2015 case definition

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