Most people have minimal symptoms or no symptoms. If symptoms do occur, they're usually mild and last around 2 to 7 days.
Commonly reported symptoms include:
Most cases of Zika virus disease are spread by infected mosquitoes biting humans.
Unlike the mosquitoes that spread malaria, affected mosquitoes (the Aedes mosquito) are most active during the day, especially during mid-morning, then late afternoon to dusk.
There have been a small number of reports of Zika virus being passed on through sexual intercourse, although the risk is thought to be low.
Before travelling, seek travel health advice from a GP, practice nurse or a travel clinic, ideally 4 to 6 weeks before you go.
You can use this A to Z guide to check if the country you're visiting has a risk for Zika virus transmission.
To reduce your risk of infection, you should avoid being bitten by an Aedes mosquito.
The most effective bite prevention methods, which should be used during daytime and night-time hours, include:
Scientists have concluded that there's enough evidence to show that Zika virus infection is a cause of birth defects, including microcephaly.
Microcephaly means the baby will have an abnormally small head and can be associated with abnormal brain development. This is also known as congenital Zika syndrome.
Specific recommendations for pregnant women considering travel to affected countries or areas can be found in the "other risks" section of the NaTHNaC country information pages.
Discuss your travel plans with a GP, practice nurse or travel clinic. If travel is unavoidable, you should take extra care to avoid being bitten by mosquitoes.
If you and your partner are currently in an area with a risk of Zika virus transmission, make sure you use condoms during vaginal, anal and oral sex while travelling and for the duration of your pregnancy.
If you're pregnant and have recently returned from a country or an area with a risk of Zika virus transmission, see a GP or midwife and mention where you have been, even if you have not been unwell.
Your midwife or hospital doctor will discuss the risk with you and can arrange an ultrasound scan of your baby to monitor growth.
If there are any issues, you'll be referred to a specialist foetal medicine service for further monitoring.
Zika virus is most likely to be detected by currently available tests when symptoms are present.
If you're currently experiencing Zika symptoms, contact a GP, who will decide whether investigations are necessary.
Investigations might include a blood test and an ultrasound test if you're pregnant.
Screening tests for Zika are not available for those without symptoms.
If you're trying to get pregnant, discuss your travel plans with a GP, practice nurse or travel clinic.
You should take extra care to avoid being bitten by mosquitoes.
Women should avoid becoming pregnant while travelling in a country or area with a risk for Zika virus transmission.
On returning to the UK, you should avoid becoming pregnant for a further 2 months if only the woman travelled, and for 3 months if both partners or just the male partner travelled.
If you have experienced Zika symptoms within 2 weeks of returning home, it's recommended that you wait 2 months after full recovery before you try to get pregnant.
If your male partner has travelled to an area with risk for Zika virus transmission, you should use effective contraception to prevent pregnancy.
You should also use condoms during vaginal, anal and oral sex to reduce the risk of sexual transmission.
These measures should be taken during travel and for 3 months:
There's no specific treatment for Zika virus symptoms. Drinking plenty of water and taking paracetamol may help relieve symptoms.
If you feel unwell after returning from a country that has malaria, as well as having a risk of Zika virus transmission, you should seek urgent (same day) advice to help rule out a malaria diagnosis.
If you remain unwell and malaria has been shown not to be the cause, seek medical advice.
As a precaution, the NHS Blood and Transplant service has recommended that people who have travelled to areas with a risk of Zika virus transmission wait 28 days before donating blood.
If you want to know whether any recent foreign travel temporarily bars you from giving blood, you can call their National Contact Centre on 0300 123 23 23.
Scientists now believe that Zika virus is a cause of Guillain-Barré syndrome (GBS), a serious condition of the nervous system.
The risk of developing GBS after a Zika virus infection is currently unknown, but thought to be very low.
If you have been infected with the Zika virus, your clinical team will pass on information about you to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).
This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.