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Zika virus disease: Questions and answers

Where does Zika virus occur?

Zika virus occurs in tropical areas with large mosquito populations, and is known to circulate in Africa, the Americas, Southern Asia and Western Pacific.

Zika virus was discovered in 1947, but for many years only sporadic human cases were detected in Africa and Southern Asia. In 2007, the first documented outbreak of Zika virus disease occurred in the Pacific. Since 2013, cases and outbreaks of the disease have been reported from the Western Pacific, the Americas and Africa. Given the expansion of environments where mosquitoes can live and breed, facilitated by urbanisation and globalisation, there is potential for major urban epidemics of Zika virus disease to occur globally.

How do people catch Zika virus?

People catch Zika virus by being bitten by an infected Aedes mosquito – the same type of mosquito that spreads dengue, chikungunya and yellow fever.

What are the symptoms of Zika virus disease?

Zika virus usually causes mild illness; with symptoms appearing a few days after a person is bitten by an infected mosquito. Most people with Zika virus disease will get a slight fever and rash. Others may also get conjunctivitis, muscle and joint pain, and feel tired. The symptoms usually finish in 2 to 7 days.

What might be the potential complications of Zika virus?

Because no large outbreaks of Zika virus were recorded before 2007, little is currently known about the complications of the disease.

During the first outbreak of Zika from 2013 – 2014 in French Polynesia, which also coincided with an ongoing outbreak of dengue, national health authorities reported an unusual increase in Guillain-Barré syndrome. Retrospective investigations into this effect are ongoing, including the potential role of Zika virus and other possible factors. A similar observation of increased Guillain-Barré syndrome was also made in 2015 in the context of the first Zika virus outbreak in Brazil.

In 2015, local health authorities in Brazil also observed an increase in babies born with microcephaly at the same time of an outbreak of Zika virus. Health authorities and agencies are now investigating the potential connection between microcephaly and Zika virus, in addition to other possible causes. However more investigation and research is needed before we will be able to better understand any possible link.

Should pregnant women be concerned about Zika?

Health authorities are currently investigating a potential link between Zika virus in pregnant women and microcephaly in their babies. Until more is known, women who are pregnant or planning to become pregnant should take extra care to protect themselves from mosquito bites.

If you are pregnant and suspect that you may have Zika virus disease, consult your doctor for close monitoring during your pregnancy.

What is microcephaly?

Microcephaly is a rare condition where a baby has an abnormally small head. This is due to abnormal brain development of the baby in the womb or during infancy. Babies and children with microcephaly often have challenges with their brain development as they grow older.

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

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. There is currently no cure or vaccine for the disease itself.

How is Zika virus disease diagnosed?

For most people diagnosed with Zika virus disease, diagnosis is based on their symptoms and recent history (e.g. mosquito bites, or travel to an area where Zika virus is known to be present). A laboratory can confirm the diagnosis by blood tests.

What can I do to protect myself?

The best protection from Zika virus is preventing mosquito bites. Preventing mosquito bites will protect people from Zika virus, as well as other diseases that are transmitted by mosquitoes such as dengue, chikungunya and yellow fever.

This can be done by using insect repellent; wearing clothes (preferably light-coloured) that cover as much of the body as possible; using physical barriers such as screens, closed doors and windows; and sleeping under mosquito nets. It is also important to empty, clean or cover containers that can hold water such as buckets, flower pots or tyres, so that places where mosquitoes can breed are removed.

Should I avoid travelling to areas where Zika virus is occurring?

Travellers should stay informed about Zika virus and other mosquito-borne diseases and consult their local health or travel authorities if they are concerned.

To protect against Zika virus and other mosquito-borne diseases, everyone should avoid being bitten by mosquitoes by taking the measures described above. Women who are pregnant or planning to become pregnant should follow this advice, and may also consult their local health authorities if travelling to an area with an ongoing Zika virus outbreak.

Based on available evidence, WHO is not recommending any travel or trade restrictions related to Zika virus disease. As a precautionary measure, some national governments may make public health and travel recommendations to their own populations, based on their assessments of the available evidence and local risk factors.

What is WHO doing?

To help countries prepare for and respond to Zika, WHO is working with ministries of health to improve laboratory capacity to detect the virus, providing recommendations for clinical care and follow-up of infected patients (in collaboration with national professional associations and experts), and encouraging monitoring and reporting on the virus’s spread and the emergence of complications.

WHO is also coordinating with countries that have reported outbreaks of Zika virus and other partners to investigate the potential relationships between Zika and microcephaly and other issues.