Zika virus and potential complications: Questions and answers

Views: 11     Author: Site Editor     Publish Time: 2016-03-06      Origin: WHO

Zika virus and potential complications: Questions and answers


Online Q&A
10 March 2016

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. Evidence is growing that Zika virus causes both microcephaly and Guillain-Barré syndrome.   

Zika virus

How do people catch Zika virus?

Zika virus is primarily transmitted to people through the bite of an infected Aedes mosquito, which also transmits chikungunya, dengue and yellow fever. Zika virus can also be transmitted through sex.

Zika virus has been detected in blood, urine, amniotic fluids, semen, saliva as well as body fluids found in the brain and spinal cord.

Where does Zika virus occur?

Local transmission of Zika virus by Aedes mosquito has been reported on the continents of Africa, the Americas, Asia and the Pacific.

There are 2 types of Aedes mosquito capable of transmitting the Zika virus. In most cases, Zika is spread through the Aedes aegypti mosquito in tropical and subtropical regions. The Aedes albopictus mosquito also transmits the virus and can hibernate to survive regions with cooler temperatures.

Can El Niňo have an effect on Zika transmission?

The Aedes aegypti mosquito breeds in standing water. Severe drought, flooding, heavy rains and temperature rises are all known effects of El Niño—which is the result of a warming of the central to eastern tropical Pacific Ocean. An increase in mosquitoes can be expected due to expanding and favourable breeding sites. Steps can be taken to prevent and reduce the health effects of El Niño.

More on El Niño and Zika

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

The Aedes mosquito is a weak flyer; it cannot fly more than 400 meters. However it may be possible for the mosquito to be transported from one place to another accidentally and introduce Zika virus to new areas.

What are the symptoms of Zika virus disease?

Zika virus usually causes mild illness. Symptoms most commonly include a slight fever or rash, appearing a few days after a person is bitten by an infected mosquito. Although many will not develop any symptoms at all, others may also suffer from conjunctivitis, muscle and joint pain, and feel tired. The symptoms usually last from 2 to 7 days.

There is no known difference in the symptoms of infected pregnant and non-pregnant women.

How is Zika virus disease diagnosed?

Diagnosis is based on symptoms and the person’s recent history (e.g. mosquito bites, or travel to an area where Zika virus occurs). Laboratory testing can confirm the presence of Zika virus in the blood. However, this diagnosis may not be reliable as the virus could cross-react with other viruses such as dengue, West Nile and yellow fever.

How is Zika virus disease treated?

The symptoms of Zika virus disease can be treated with common pain and fever medicines, rest and plenty of water. If symptoms worsen, people should seek medical advice.

Mosquito protection

What can people do to protect themselves from mosquito bites?

The best protection from Zika virus is preventing mosquito bites. Women who are pregnant or planning to become pregnant and their sexual partners should take extra care to protect themselves from the bites of the mosquito that transmits Zika. This can be done by:

Wearing clothes (preferably light-coloured) that cover as much of the body as possible.

Using insect repellent: repellents may be applied to exposed skin or to clothing, and should contain DEET (diethyltoluamide) or IR 3535 or Icaridin which are the most common biologically active ingredients in insect repellents. Repellents must be used in strict accordance with the label instructions. They are safe for use by pregnant women.

Using physical barriers such mesh screens or treated netting materials on doors and windows.

Sleeping under mosquito nets, especially when resting during the day, when Aedes mosquitoes are most active.

Identifying and eliminating potential mosquito breeding sites, by emptying, cleaning or covering containers that can hold even small amounts of water, such as buckets, flower pots and tyres.

How can pregnant women protect themselves from mosquito bites?

Pregnant women living in areas of Zika virus transmission should follow the same prevention guidelines as the general population.

Pregnant women living in areas with ongoing Zika virus transmission should attend their regular antenatal care visits in accordance with national standards and comply with the recommendations of their health-care providers. They should also start antenatal care visits early for diagnosis and appropriate care and follow-up if they develop any of the Zika symptoms or signs.

Sexual transmission

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

All people who have been infected with Zika virus and their sexual partners—particularly pregnant women—should receive information about the risks of sexual transmission of Zika virus, contraceptive options and safer sexual practices. When feasible, they should have access to condoms and use them correctly and consistently.

Pregnant women’s sex partners living in or returning from areas where local transmission of Zika virus occurs should practice safer sex, wearing condoms, or abstaining throughout the pregnancy.

People living in areas where local transmission of Zika virus occurs should practice safer sex or abstain from sexual activity.

In addition, people returning from areas where local transmission of Zika virus occurs should adopt safer sexual practices or consider abstinence for at least 4 weeks after their return to reduce the risk of onward transmission.

Information for the general public:
Information for policy-makers:
Information for health-care providers:

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?

All women and girls should have ready access to emergency contraception, including accurate information and counselling as well as affordable methods. 

Advice for general public:


What should people travelling to Zika-affected areas do?

Travellers should stay informed about Zika virus and other mosquito-borne diseases, such as chikungunya, dengue and yellow fever, and consult their local health or travel authorities if they are concerned.

Pregnant women should be advised not to travel to areas of ongoing Zika virus transmission; pregnant women whose sexual partners live in or travel to areas with Zika virus transmission should ensure safer sexual practices or abstain from sex for the duration of their pregnancy.

More on travelling in the context of Zika

Guillain-Barré syndrome and microcephaly

Are fetal malformations and neurological disorders linked to Zika virus?

Substantial new research has strengthened the association between Zika infection and fetal malformations and neurological disorders. During the first outbreak of Zika from 2013 - 2014 in French Polynesia national health authorities reported an unusual increase in Guillain-Barré syndrome. During 2015 and 2016, several countries and territories have reported an increase in people with Guillain-Barré syndrome and/or laboratory confirmation of Zika virus infection among people with Guillain-Barré syndrome.

So far an unusual increase in microcephaly cases and other neonatal malformations has been reported in Brazil and French Polynesia. However, microcephaly is now only one of several documented birth abnormalities associated with Zika infection during pregnancy.

More investigation and research is needed to establish causal relationships. Other potential causes are also being investigated.

What is Guillain-Barré syndrome?

Guillain-Barré syndrome is a rare condition in which a person’s immune system attacks his or her nerves. People of all ages can be affected, but it is more common in adult men. Most people recover fully from even the most severe cases of Guillain-Barré syndrome. In 20%-25% of people with the condition, the chest muscles are affected, making it hard to breathe. Severe cases of Guillain-Barré syndrome are rare, but can result in paralysis.

Fact sheet: Guillain-Barré syndrome

What is microcephaly?

Microcephaly is a condition where a baby’s head is smaller than those of other babies of the same age and sex. Microcephaly happens when there is either a problem in utero, causing the baby’s brain to stop growing properly, or after birth when the head stops growing properly.

Children born with microcephaly often have developmental challenges as they grow older. In some cases, children with microcephaly develop entirely normally.

Microcephaly can be caused by a variety of environmental and genetic factors such as Down syndrome; exposure to drugs, alcohol or other toxins in the womb; and rubella infection during pregnancy.

Information for the general public:
Information for health-care providers:


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

Transmission of Zika virus from pregnant women to their fetuses has been documented.

Zika virus infection close to term could potentially be transmitted during both pregnancy and at childbirth, although this has not been scientifically proven to date.

Pregnant women in general, including those who develop symptoms of Zika virus infection, should see their health-care provider for close monitoring of their pregnancy.

Can mothers with Zika infection breastfeed their baby?

Zika virus has been detected in breast milk but there is currently no evidence that the virus is transmitted to babies through breastfeeding.

WHO recommends exclusive breastfeeding for the first 6 months of life.

Fact sheet: Breastfeeding

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

Whether and when to become pregnant should be a personal decision, on the basis of full information and access to affordable, quality health services.

Women wanting to postpone pregnancy should have access to a comprehensive range of reversible, long- or short-acting contraceptive options. They should also be counselled on the dual protection against sexually transmitted infections provided by condoms.

There are no known safety concerns regarding the use of any hormonal or barrier contraceptive methods for women or adolescent girls at risk of Zika virus, women diagnosed with Zika virus infection, or women and adolescents being treated for Zika virus infection.

Information for policy makers:

What should pregnant women do if they wish to discontinue their pregnancy due to a fear of microcephaly?

Most women in Zika-affected areas will give birth to normal infants.

Early ultrasound does not reliably predict microcephaly. WHO recommends a repeat ultrasound of the fetus in the late second or early third trimester (preferably between 28 and 30 weeks) to identify fetal microcephaly and/or other brain abnormalities when they are easier to detect.

Where feasible, screening of amniotic fluid (a pregnant woman's waters) for abnormalities and congenital infections, including Zika virus, is recommended, especially in cases where women tested negative for Zika but their ultrasounds indicate fetal brain abnormalities.

Based on the prognosis of associated fetal brain abnormalities, the woman—and her partner if she wishes—should be offered non-directive counselling so that she, in consultation with her health-care provider, can make a fully informed choice about the next steps in the management of her pregnancy.

Women who wish to discontinue the pregnancy should receive accurate information about their options to the full extent of the law, including harm reduction where the care desired is not readily available.

Women, whatever their individual choices with respect to their pregnancies, must be treated with respect and dignity.

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