WHO Priority diseases: Zika virus infections

Zika is a disease caused by the Zika virus. It was first discovered in 1947 and is named after the Zika Forest in Uganda. The disease was first detected in humans in 1952. Since then, outbreaks have occurred in tropical Africa, Southeast Asia, and the Pacific Islands.

The most recent outbreak of Zika occurred in early 2015 in Brazil, which spread to South and North America, several islands in the Pacific, and Southeast Asia. In February 2016, WHO declared the outbreak a Public Health Emergency of International Concern as evidence grew that Zika can cause birth defects as well as neurological problems. This outbreak was officially declared as over in November 2016 by the WHO. This 2015-16 outbreak also affected the 2016 Summer Olympics held in Rio de Janeiro.

Zika was also reported from India last year. Three laboratory-confirmed cases (RT-PCR) of Zika virus disease were reported in Bapunagar area, Ahmedabad District, Gujarat, State, India providing evidence of the circulation of the virus in India. These cases emphasize the need for active surveillance for the virus.

  • Zika spreads mainly by the bite of the infected Aedes mosquitoes, which also transmit dengue and Chikungunya. Zika can be passed from a pregnant woman to her fetus and through unprotected sex. The virus may spread through blood transfusion.
  • Clinical presentation: Most cases of Zika are either asymptomatic or have only mild symptoms, which can remain for up to a week. The symptoms include fever, skin rash, conjunctivitis (red eyes) headache, malaise, joint and muscle pain.
  • Infection during pregnancy can cause microcephaly and other severe brain defects, including stillbirths, miscarriages. Zika virus is a trigger of Guillain-Barré syndrome.
  • Zika virus has been detected in whole blood (also serum and plasma), urine, cerebrospinal fluid, amniotic fluid, semen and saliva. The virus persists in urine and semen for longer periods than in whole blood or saliva.
  • A relevant travel history, symptoms should raise the suspicion of Zika infection. The diagnosis can be confirmed by laboratory tests. Specimens for testing include whole blood/serum and/or urine.

o    In patients presenting with symptom onset <7 days: Nucleic acid testing (NAT) is recommended.

o    In patients presenting with symptom onset ≥7 days: Serology (IgM detection; preferred method) and/or NAT is recommended. As per the WHO, a negative NAT does not rule out the infection because viremia drops rapidly 7 days after onset of symptoms and so may not be detectable on NAT.

  • Treatment: There is no specific treatment. Supportive care includes plenty of rest, adequate fluid intake, symptomatic treatment of pain and fever.
  • Prevention: There is no vaccine yet for Zika. Hence, prevention of Zika is by protection against mosquito bites.

(Source: CDC, WHO)

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