Zika virus and complications: Questions and answers

Online Q&A
Updated 17 May 2016

Summary of the situation

Zika virus is a mild disease and most people with the virus do not have symptoms. However, the recent rise in the spread of Zika virus in Brazil has been accompanied by an unprecedented rise in the number of children being born with unusually small heads—identified as microcephaly. In addition, several countries, including Brazil, reported a steep increase in Guillain-Barré syndrome—a neurological disorder that could lead to paralysis and death. Based on research, there is scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barré syndrome.

*Click on the questions below to view the answer.

Zika virus

How do people catch Zika virus?

Where does Zika virus occur?

Can El Niňo have an effect on Zika transmission?

Can the Aedes mosquito travel from country to country and region to region?

What are the symptoms of Zika virus disease?

How is Zika virus disease diagnosed?

How is Zika virus disease treated?

Olympic and Paralympic Games Rio, 2016

New! What are the risks facing athletes and visitors attending the Olympic and Paralympic Games in Rio, Brazil in 2016 with regard to the current Zika outbreak?

New! What can athletes and visitors do to protect themselves?

New! Should pregnant women attend the Rio 2016 Games? And what about their partners?

New! Based on the current situation in Brazil, does WHO recommend the Olympic and Paralympic Games should go ahead?

Mosquito protection

What can people do to protect themselves from mosquito bites?

How can pregnant women protect themselves from mosquito bites?

Mosquito surveillance (monitoring)

What role does mosquito surveillance play in addressing Zika virus?

What proportion of Aedes Aegypti mosquitoes have to be infected with Zika virus to create major breakouts such as the ones we are seeing in the Americas?

Why is WHO focusing on the Aedes mosquito as the primary vector for Zika? Is enough known to warrant the current design of the vector control program?

Is it possible that another species of mosquito, the Culex for example, could be involved in the Zika virus epidemic?

Is there national or international research underway into the Zika virus to look at all the possible causes?

Where can I find more information about mosquito surveillance?

Sexual transmission

What can people do to be protected from sexual transmission of Zika virus?

What should women do if they have been exposed to unprotected sex but do not wish to become pregnant because of possible infection with Zika?


What should people travelling to Zika-affected areas do?

Guillain-Barré syndrome, microcephaly and other neurological disorders

New! Is Zika virus a cause of microcephaly and Guillain-Barré syndrome?

New! What events led WHO to investigate a causal link?

New! Are there other explanations for microcephaly and Guillain-Barré syndrome?

New! Is there a link between Zika and other neurological disorders?

What is Guillain-Barré syndrome?

What is microcephaly?


Can women transmit Zika virus to their fetuses during pregnancy or childbirth?

Can mothers with Zika infection breastfeed their baby?

New!What should women do if they wish to postpone pregnancy because they are worried about microcephaly?

How can women manage their pregnancy in the context of Zika virus and complications?

Zika virus response

New! What is the WHO response to Zika?

New! What are WHO recommendations to countries?

How can the Zika response keep up with all the new research being published?

References: i

Besnard M, Lastere S, Teissier A, Cao-Lormeau V, Musso D. Evidence of perinatal transmission of Zika virus, French Polynesia, December 2013 and February 2014. Eurosurveillance 2014 Apr 3;19(13):20751. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20751

Brasil P, Pereira JP, Raja Gabaglia C, Damasceno L, Wakimoto M, Ribeiro Nogueira RM, et al. Zika Virus Infection in Pregnant Women in Rio de Janeiro - Preliminary Report. N Engl J Med 2016 Mar 4 [cited 2016 Mar 6];NEJMoa1602412. Available from: http://www.nejm.org/doi/10.1056/NEJMoa1602412

Broutet N, Krauer F, Riesen M, Khalakdina A, Almiron M, Aldighieri S, et al. Zika virus as a cause of neurologic disorders. N Engl J Med: Mar 9 2016. Available from: http://www.nejm.org/doi/full/10.1056/NEJMp1602708#t=article

Cao-Lormeau V-M, Blake A, Mons S, et al. Guillain-Barré Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Lancet 2016;Published Online February 29, 2016 http://dx.doi.org/10.1016/ S0140-6736(16)00562-6.

Cauchemez S, Besnard M, Bompard P, Dub T, Guillemette-Artur P, Eyrolle-Guignot D, et al. Association between Zika virus and microcephaly in French Polynesia, 2013-15: a retrospective study. Lancet 2016 Mar 15; Available from: http://www.ncbi.nlm.nih.gov/pubmed/26993883

Dick GWA. Zika virus. II. Pathogenicity and physical properties. Trans R Soc Trop Med Hyg 1952 Sep;46(5):521–34. Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=emed1aa&NEWS=N&AN=12995441

European Centre for Disease Prevention and Control ECDC. Epidemiological update: Complications potentially linked to the Zika virus outbreak, Brazil and French Polynesia - 27 November 2015 [Internet]. 2015. Available from: http://ecdc.europa.eu/en/press/news/_layouts/forms/News_DispForm.aspx?ID=1332&List=8db7286c-fe2d-476c-9133-18ff4cb1b568&Source=http://ecdc.europa.eu/en/press/epidemiological_updates/Pages/epidemiological_updates.aspx

European Centre for Disease Prevention and Control ECDC. Rapid risk assessment: Zika virus disease epidemic: potential association with microcephaly and Guillain-Barré syndrome. 21 January 2016 [Internet].

Heymann DL, Hodgson A, Sall AA, et al. Zika virus and microcephaly: why is this situation a PHEIC? Lancet 2016;387:719-21. Ioos S, Mallet H-P, Leparc Goffart I, Gauthier V, Cardoso T, Herida M. Current Zika virus epidemiology and recent epidemics. Médecine Mal Infect 2014 Jul;44(7):302–7. Available from: http://www.elsevier.com/journals/medecine-et-maladies-infectieuses/0399-077X

Oehler E, Watrin L, Larre P, Leparc-Goffart I, Lastere S, Valour F, et al. Zika virus infection complicated by Guillain-Barre syndrome--case report, French Polynesia, December 2013. Eurosurveillance 2014 Mar 6;19(9):20720. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20720

Petersen LR, Jamieson DJ, Powers AM, Honein MA. Zika virus. N Engl J Med: 30 March 2016. Available at: http://www.nejm.org/doi/full/10.1056/NEJMra1602113

Reefhuis J, Gilboa SM, Johansson MA, Valencia D, Simeone RM, Hills SL, et al. Projecting Month of Birth for At-Risk Infants after Zika Virus Disease Outbreaks. Emerg Infect Dis 2016 May [cited 2016 Mar 6];22(5). Available from: http://wwwnc.cdc.gov/eid/article/22/5/16-0290_article.htm

Rothman KJ, Greenland S. Causation and causal inference in epidemiology. American Journal of Public Health 2005;95 Suppl 1:S144-50.

Vandenbroucke JP. In defense of case reports and case series. Annals of Internal Medicine 2001;134:330-4.