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 the Zika virus and other mosquito-borne diseases, everyone should avoid being bitten by mosquitoes
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.
People catch Zika virus by being bitten by an infected Aedes mosquito—the same type of mosquito that spreads dengue, chikungunya and yellow fever.
Only female mosquitoes bite; they are intermittent feeders and prefer to bite more than one person. Once the female mosquito is fully fed, it needs to rest three days before it lays eggs. The eggs can survive up to one year without water. Once water is available, and small quantities of standing water are sufficient, the eggs develop into larvae and then the adult mosquitoes. Mosquitoes get infected from people with the virus.
There are two types of Aedes mosquito capable of transmitting the Zika virus. In most cases, Zika spreads through the Aedes aegypti mosquito in tropical and subtropical regions. The Aedes aegypti mosquito does not survive in cooler climate temperatures. The Aedes albopictus mosquito can also transmit the virus. This mosquito can hibernate and survive cooler temperature regions.
The Aedes mosquito is a weak flyer; it cannot fly more than 400 metres. But it may inadvertently be transported by humans from one place to another (e.g. in the back of the car, plants). If it can survive the temperature climate of the destination, it may theoretically be capable of reproducing itself there and introduce Zika virus to new areas.
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 two to seven days.
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—14 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.
Guillain-Barré syndrome is a condition in which the body’s immune system attacks part of the nervous system. It can be caused by a number of viruses and can affect people of any age. Exactly what triggers the syndrome is not known.
The main symptoms include muscular weakness and tingling in the arms and legs. Severe complications can occur if the respiratory muscles are affected, requiring hospitalisation.
Most people affected by Guillain-Barré syndrome will recover, although some may continue to experience effects such as weakness.
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.
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 down syndrome; exposure to drugs, alcohol or other toxins in the womb; and rubella infection during pregnancy.
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
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 even small amounts of water such as buckets, flower pots or tyres, so that places where mosquitoes can breed are removed.
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.
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 have made public health and travel recommendations to their own populations, based on their assessments of the available evidence and local risk factors.
