What is the Zika virus?
The Zika virus is a virus that causes an infectious disease called Zika fever. Only one in five people infected with the Zika virus will develop symptoms. Generally, the symptoms are quite mild. Scientists agree that infection with the Zika virus can be harmful to unborn children. Six per cent of such children are born with neurological birth defects such as microcephaly. Alternatively, infection with the virus may result in the child being born with Guillain-Barré syndrome.
Where is the Zika virus endemic?
The Zika virus has been around for a while in Africa, Asia and the countries in and around the Indian Ocean. There was a very significant outbreak of the Zika virus in Central and South America, the southern part of North America and the Caribbean in 2015 and 2016. By 2019, this outbreak was largely over. As a result, the risk of being infected with the Zika virus has decreased sharply.
So far, the only cases of Zika virus infection reported in the Netherlands have been imported from other countries. Since yellow fever mosquitoes (Aedes aegypti), which also spread dengue, are not native to the Netherlands, the likelihood of the Zika virus spreading here is negligible.
In mid-October 2018, the WHO announced it was going to stop updating its overview of countries where the Zika virus had been reported. The National Travel Safety Advice Coordination Centre keeps track of places in individual countries where people are at increased risk of Zika virus infection.
What kinds of symptoms to expect after a Zika virus infection
Approximately one in five persons develop symptoms after being infected with the Zika virus. Generally, Zika virus symptoms develop three to 12 days after the patient is bitten by an infected mosquito. Most people recover within a week and do not experience any serious problems.
The following symptoms may occur:
- Acute fever (typically mild)
- Eye infection without discharge
- Muscle ache and joint pain (particularly in the hands and feet), with joint swelling in some cases
- Skin rash (which often first develops in the face, then spreads to other parts of the body)
- Less common: headache, lack of appetite, vomiting, diarrhoea and stomach ache
Severe symptoms are very rare, but do occur:
- Birth defects in unborn children due to Zika virus infection during pregnancy, also known as congenital Zika virus syndrome. Among other things, children born with this syndrome have a neurological birth defect (microcephaly). About 6% of such children developed congenital defects.
- Guillain-Barré Syndrome It is not yet known how common this syndrome is following Zika virus infection, but it appears to be quite rare.
How to prevent being infected with the Zika virus
The Zika virus is transmitted by certain types of mosquitoes that are very common in and around the house in the tropics and subtropics. The virus is mainly spread by yellow fever mosquitoes, also known as dengue mosquitoes (Aedes aegypti). This type of mosquito mainly feeds on human blood and bites people between sunrise and sunset. In other words, it also bites people during the day.
If you are travelling to regions in which these mosquitoes are endemic, it is vital that you take preventative measures to avoid being bitten by mosquitoes during the day and in the early evening.
- Wear clothes that cover your skin (long sleeves, long trousers)
- Apply a mosquito repellent containing diethyltoluamide (DEET) to those parts of your skin that are exposed. Children under the age of two and pregnant women should not use any products whose DEET content exceeds 30%.
- Be sure to sleep under a mosquito net (preferably impregnated with mosquito repellent) or in a room free from mosquitoes.
Travellers are at increased risk of contracting diseases transmitted by mosquitoes, such as Zika, but also chikungunya, dengue fever and malaria. In particular, pregnant women and women who wish to have children are at increased risk. They are advised to consult either a specialist at a travel clinic or their treating physician on their travel plans before departure. They can then decide in consultation with the consultant at the travel clinic whether or not travelling to this region is a good idea. You can find more information on diseases affecting travellers can be found on the website of the National Travel Safety Advice Coordination Centre (in Dutch).
In very rare cases, the Zika virus can be transmitted sexually, as the virus has been found in sperm. However, doctors think it is highly unlikely that people can be infected with the Zika virus in this way. Since the risk of getting infected with Zika virus by mosquitoes has decreased sharply in recent years, the risk of sexual transmission has decreased even further.
Travel safety advice for pregnant women and women who wish to have children
In countries where mosquitoes that transmit the Zika virus are endemic, pregnant women and women who wish to have children may be infected with the virus. The chances of this happening are slight, but if you do get infected, the consequences for your baby may be severe. Studies have shown that 6% of such babies had congenital birth defects, such as microcephaly.
Prior to departure, be sure to visit a travel safety advice and vaccination clinic for recommendations tailored to your specific situation. Discuss the arguments for and against travelling with the travel safety consultant. Do not just discuss the Zika virus, either; be sure to discuss other tropical and subtropical infections (such as malaria and dengue), as well. You can find more information on the risks associated with each individual country can be found on the following websites: lcr.nl and ggdreisvaccinaties.nl.
Zika virus epidemic in South and Central America
A major outbreak of the Zika virus began in May 2015 in Brazil. From there, the virus spread across various countries in South and Central America, including the Caribbean, and became an epidemic. The first signs that infection with the Zika virus during pregnancy might be harmful to unborn children were observed in November 2015. By now, it has been scientifically proven that the Zika virus causes adverse effects on unborn children.
Starting from 1 November 2016, doctors in the Netherlands were required to report Zika virus infection in pregnant women, as well as complicated infections. The Zika virus is unlikely to spread within the Netherlands because the mosquitoes that transmit the virus are not native to the Netherlands.
Why did the Brazilian Zika virus outbreak get so bad?
The Zika virus made it to South and Central America for the first time in 2015. The mosquitoes (yellow fever mosquitoes) that can spread this virus were extremely common there. Prior to 2015, no one in South and Central America had been infected with Zika virus. As a result, no one was immune to the virus yet. Once the Zika virus had infected humans, the local mosquitoes spread the virus further. After all, this type of mosquitoes feeds on human blood. This resulted in a major Zika virus outbreak.
The virus was first identified in 1947, in Africa. As far as we know, the virus has never caused such large epidemics there. The virus was first found in Micronesia in 2007, and in French Polynesia in 2013.