Zika Virus Infection
Zika infection is caused by the Zika virus (ZIKV).
Infection is spread by the bites of the Aedes species of mosquitoes. These mosquitoes predominantly bite during the day, and can also transmit dengue fever, chikungunya fever and yellow fever.
Rarely ZIKV can be transmitted sexually.
Infection during pregnancy can lead to congenital zika syndrome, with severe consequences for the baby.
ZIKV was first discovered in Africa in 1947, and had been occasionally noted in countries in Africa and Asia since then. The first ever outbreak of ZIKV occurred in the Federated States of Micronesia in 2007. This was followed by outbreaks in the Pacific islands from 2013 and a large outbreak in 2015/2016 that affected the whole of Central/South America, the Caribbean and some parts of North America.
Most people infected with ZIKV will have only very mild, or no symptoms. Symptoms usually start 2-12 days after the bite of an infected mosquito and last for 4-7 days. They include: rash, itch, mild fever, headache, red eyes, muscle and joint pains. Other less common symptoms include: loss of appetite, diarrhoea, constipation, abdominal pain and dizziness.
There is no specific treatment for ZIKV infection available. Most people will get better without any treatment. Symptoms like headache and fever can be treated symptomatically. Hospital care is indicated in severe illnesses or if complications arise.
There is no medicine or vaccine currently available that prevents ZIKV infection.
Travellers are advised to seek travel advice from a health care provider at least 6-8 weeks in advance of travel, but particularly important if you are pregnant or planning pregnancy.
All travellers to countries with a risk of ZIKV transmission must consider:
- Mosquito Bite Avoidance measures.
- Travel Insurance.
- Any additional travel recommendations for pregnant travellers, those planning pregnancy and for preventing onward sexual transmission.
Mosquito Bite Avoidance
Strict Bite avoidance measures are recommended for all travellers, especially pregnant women. Aedes mosquitoes are particularly persistent and aggressive biters.
- 50% DEET- based insect repellents should be applied regularly (according to manufacturers instructions).
- DEET is appropriate for use in pregnancy.
- If DEET is unsuitable then another, proven alternative should be used.
- Wearing loose, cover-up clothing is recommended.
- Clothing can be impregnated or sprayed with the insecticide permethrin.
- Insecticide-impregnated bed nets and air conditioning should be used in bedrooms.
- Reduction of mosquito breeding sites around hotel rooms/homes is advised for longer-term stays.
Travellers should be strongly advised not to travel without adequate insurance.
- Pregnant women should check with their travel insurance company that they are covered under the policy before booking their trip.
Pregnant women should be aware that the risk of ZIKV in any country may change during the time between planning the trip and travelling.
Additional Travel Recommendations
These are based on the transmission risk of ZIKV in a country.
High Risk or Moderate Risk of ZIKV transmission (check A-Z list here).
- Postpone non-essential travel to High risk countries.
- Consider postponing non-essential travel to Moderate risk countries.
Pregnant women should discuss the risk of ZIKV with their travel healthcare provider so they can make a fully informed decision regarding travel. Pregnant women should:
- Remember that malaria and other travel related hazards may pose a risk during pregnancy
- Use condoms to prevent sexual transmission of ZIKV during travel and throughout the pregnancy.
- On return, seek early obstetric review, even if well.
Those planning pregnancy, or where there is a Risk of Pregnancy
Avoid the risk of ZIKV in pregnancy and sexual transmission of ZIKV by the use of contraception and condoms during travel and for:
- 8 weeks afterwards if female
- 6 months afterwards if male.
Low Risk of ZIKV transmission (check A-Z list here).
Pregnant women and those planning pregnancy
Pregnant women and those planning pregnancy should discuss the risk of ZIKV infection and its association with adverse pregnancy outcomes with their travel health provider before deciding whether to continue with their travel plans.
Medical attention must be sought quickly for any feverish illness experienced whilst travelling or on return home. Remember that other travel related hazards, including malaria, may be present in ZIKV affected countries, and can be serious, particularly if you are pregnant.
Travellers returning from countries with a High/Moderate risk of ZIKV transmission, or who have been diagnosed with ZIKV should use contraception and follow guidelines for reducing sexual transmission as detailed above.
Travellers returning from countries affected by ZIKV cannot donate blood for 4 weeks after return if they have had no symptoms, or 6 months if they have had symptoms of ZIKV infection. UK Blood Transfusion Services have a policy of 28 day deferral for donors who have visited Zika affected countries, and also for sexual partners of anyone who has been diagnosed with ZIKV infection (in the six months before sexual contact). This is a precautionary measure to protect the blood supply, particularly in relation to pregnant women.
- For answers to commonly asked questions see NHS Choices Zika Virus: Your Questions Answered.
- Mosquito Bite Avoidance leaflet for travellers
- Public Health England Leaflet - Health advice for women returning from areas with high or moderate risk of Zika virus transmission. (updated August 2017)