Updated on April, 1st 2016

These are interim case definitions based on data obtained from the current epidemic in the Region of the Americas and may be subject to modifications based on advances in knowledge about the disease and the etiologic agent.


Suspected case of Zika virus disease

Patient with rash* with two or more of the following signs or symptoms:
  • fever, usually <38.5 ° C
  • conjunctivitis (non-purulent/hyperemic)
  • arthralgia
  • myalgia
  • peri-articular edema
*usually pruritic and maculopapular

Suspected case of Zika virus disease in geographic areas without autochthonous transmission and where there are no vectors present

Patient who meets the criteria for a suspected case (above) AND who
  • in the 2 weeks prior to onset, traveled to, or resided in, a geographic area where there is known local transmission of the Zika virus or there is known vector presence;  OR
     
  • had un-protected sex, in the 2 weeks prior to onset, with a person who traveled, in the previous 8 weeks, to a geographic area with (a) known local transmission of the Zika virus or (b) and area with known vector presence.
 

Probable case of Zika virus disease

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

Confirmed case of Zika virus disease

Patient who meets the criteria for a suspected case AND has laboratory confirmation of recent Zika virus infection, i.e.:
  • RNA or Zika virus antigen in any specimen (serum, urine, saliva, tissue or whole blood);  OR
  • Positive Zika IgM antibodies AND Plaque reduction neutralization (PRNT90) for Zika virus titers = 20 and four or more times greater than the titers for other flaviviruses; AND exclusion of other flavivirus; OR
  • In autopsy specimens, detection of the viral genome (in fresh or paraffin tissue) by molecular techniques, or detection by immuno-histochemistry.
 

Guillain-Barré Syndrome (GBS) associated with Zika virus  

Suspected case of Zika-virus-associated GBS

Patient who 
  • resides in, or recently traveled to, an area where there are vectors for the Zika virus; OR 
  • has had unprotected sex with someone who resides in, or recently traveled to an area of circulation of vectors for the Zika virus; 
AND 
 
presents the following signs and symptoms (level 3 Brighton criteria):
    • Bilateral and flaccid weakness of the limbs; AND
    • Decreased or absent deep tendon reflexes in weak limbs; AND 
    • Monophasic illness pattern; and interval between onset and nadir of weakness between 12 hours and 28 days; and subsequent clinical plateau; AND
    • Absence of identified alternative diagnosis for weakness  


Confirmed case of Zika-virus-associated GBS

Patient meeting the criteria for suspected of Zika-virus-associated GBS with laboratory confirmation of recent infection with the Zika virus.

Congenital syndrome associated with Zika virus infection

Suspected case of congenital syndrome associated with Zika virus 

Live newborn who presents with: 
  • Microcephaly:  head circumference below -2 standard deviations for gestational age and sex, measured at 24 hours post-partum according to the standardized reference; OR
  • Other congenital malformation of the central nervous system; 
   AND whose mother:
  • traveled to, or resided in, an area where Zika virus vectors were present during her pregnancy; OR
  • had unprotected sex during pregnancy with a partner who resided in, or traveled to, an area with the presence of Zika virus vectors.

 

Probable case of congenital syndrome associated with Zika virus 

Live newborn who meets the criteria for a suspected case of congenital syndrome associated with Zika virus AND
  • who has intracranial morphological alterations detected by any imaging method, and not explained by other known causes; OR
  • whose mother had rash during pregnancy 
 

Confirmed case of congenital syndrome associated with Zika virus 

Live newborn who meets the criteria for a suspected case of congenital syndrome associated with Zika virus AND Zika virus infection was detected in specimens of the newborn, regardless of detection of other pathogens.

Zika-virus-associated abortion or stillbirth

Suspected Zika-virus-associated abortion or stillbirth 

Abortion or stillbirth in a woman, who during her pregnancy
  • presented rash AND
  • resided in or travelled to an area where Zika virus vectors were present; OR had unprotected sexduring pregnancy with a partner who resided in or travelled to an area where Zika virus vectors were present.


Confirmed Zika-virus-associated abortion or stillbirth 

Suspected case in which specimens from either the mother (blood or urine) or the abortion/ stillbirth are laboratory-positive for Zika virus.

Vertical transmission (without congenital syndrome)

Suspected vertical transmission (without congenital syndrome)

Live newborn of any gestational age who has not met the criteria for a suspected case of congenital syndrome associated with Zika virus AND whose mother had a suspected, probable or confirmed case of Zika infection during pregnancy. 

Probable case of vertical transmission (without congenital syndrome) 

Live newborn who meets the criteria for suspected vertical transmission in whom Zika IgM antibodies are detected by ELISA or virus RNA is detected by RT-PCR in a umbilical cord blood sample.

Confirmed case of vertical transmission (without congenital syndrome)

Live newborn who meets the criteria for suspected vertical transmission in whom anti-Zika IgM* is detected by ELISA in a serum sample of the newborn.
 
 
* When only PCR is available and it is positive, follow-up serology is advised because the viral detection could be from perinatal rather than vertical transmission.