What is the Zika virus?

Zika is a virus that began ringing public health alarm bells in May 2015, spread quickly throughout South and Central America last year, and is now threatening to reach Europe, according to the World Health Organisation (WHO). It is a mosquito-borne virus first identified in rhesus monkeys in the Zika forest of Uganda in 1947, but was first found in humans in 1952.

How is the virus spread?

Zika is an arbovirus (arthropod-borne virus), spread by bites from Aedes mosquitoes – which are also responsible for spreading other viruses such as dengue, chikungunya and yellow fever. Without mosquitoes, individual sufferers are not directly contagious, but blood-borne infection may be a possible risk and guidelines on blood donation and transfusion will need to be updated.

A small number of cases of infection have occurred through sexual transmission, and there is increasing evidence of transmission from mother to fetus.

If a person acquires Zika abroad and becomes ill on their return to the UK, any public health risk to the wider population is negligible, as the mosquito that transmits the virus is not found in the UK.

What are its effects?

Until last year Zika was thought to cause only a minor illness, with up to 80 per cent of individuals experiencing no symptoms. People with symptoms usually suffer from a fever lasting four to seven days, possibly accompanied by a rash, conjunctivitis, muscle and joint pain, and headache, commencing two to seven days following exposure.

However, during large outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, national health authorities reported potential neurological and auto-immune complications, including an increase in birth defects.

It is agreed the virus causes birth defects Credit: Getty Images

There is now a scientific consensus that Zika is a cause of microcephaly, an abormal smallness of the head associated with incomplete brain development and potentially lethal at birth, and other congenital anomalies as well as Guillain Barré syndrome, "a rare and serious condition of the peripheral nervous system", according to the NHS.

Guillain Barré syndrome (also known as GBS) is believed to be triggered by an immune reaction. Nerve damage can lead to muscle weakness, paralysis and other neurological symptoms.

The Foreign Office says, however, that "serious complications and deaths from Zika are not common".

Which countries are currently affected by Zika?

The European Centre for Disease Control (ECDC) says there are 52 countries with "active local Zika virus transmission". This is where there has been a confirmed case in the last three months, and includes much of the Caribbean, Central America and South America. Thailand is included in a Foreign Office list that stretches beyond three months to nine months.

Florida has reported a small outbreak of mosquito-transmitted Zika, prompting Public Health England (PHE) to advise pregnant women to consider postponing non-essential travel to the southern US state.

Zika does not occur in the UK. However, according to PHE, a total of 53 cases have been diagnosed in British travellers since 2015.

Could Zika reach Europe?

The WHO's European branch has said the overall risk of Zika reaching Europe is small to moderate. It is highest in areas where Aedes mosquitoes thrive, in particular on the island of Madeira, off the coast of Portugal and popular with British holidaymakers, and the north-eastern coast of the Black Sea.

It said that if no measures are taken to mitigate the threat, the presence of the Aedes aegypti mosquitoes that can carry the virus mean the likelihood of local Zika transmission is moderate in 18 countries in the region, including France, Italy, Croatia, Turkey, Greece and Spain.

What is the advice for British travellers?

The National Travel Health Network and Centre, as recommended by the Foreign Office, advises that pregnant women or those planning pregnancy "postpone non-essential travel" to areas with active Zika transmission until after pregnancy.

"Specific areas where current active Zika transmission is ongoing are often difficult to determine, and subject to change over time," it says.

"If you are travelling to regions where these diseases occur you should ideally seek travel health advice from your GP, practice nurse or a travel clinic at least four to six weeks before you travel."

More detailed advice is offered to pregnant women or those planning to get pregnant, with those who cannot avoid travel told to be "scrupulous with mosquito bite avoidance both during daytime and night hours, but especially during mid-morning and late afternoon to dusk, when the mosquito is most active".

Pregnant women who have travelled in the last nine months to areas with Zika are told to contact their GP or midwife. See here for its full advice.

There is additional guidance regarding sexual health and Zika, as the virus has been shown to be present in semen.

"The risk of sexual transmission of Zika virus is considered to be low, but the number of reports is increasing," said the Foreign Office. It advised that couples who wish to reduce the risk of transmission consider using condoms.

Travellers heading to Brazil for the Olympics should heed health authorities' advice.

Relating to Europe, there has been no update from the Foreign Office.

Workers in Rio de Janeiro spray pesticides Credit: Getty

Can I cancel my holiday?

If you have booked a holiday to a destination where there is an outbreak of Zika virus and you don’t want to travel, your right to change or get a refund for your trip will depend on how you booked it and what your circumstances are.

If you have booked your flights and accommodation independently you will have no automatic right to a refund, unless your booked a refundable ticket and a hotel with a free cancellation policy. If you have booked with a tour operator and you are pregnant, you may be entitled to cancel if the Foreign Office specifically advises against pregnant women travelling to that destination. In that case you could argue that under its legal duty of care, the operator should allow you to cancel without penalty, or perhaps offer you a suitable alternative destination.

With support from your GP, it is possible you might also be able to claim cancellation costs from your travel insurer. In practice, it is hard to imagine a tour operator penalising a pregnant woman who is worried about travelling to a Zika-infected zone.

What preventative measures are available?

Public health measures are vital to keep Aedes mosquito populations under control, but this can be notoriously difficult to achieve. There is currently no vaccine or drug to prevent infection.

There is currently no vaccine for Zika but you can reduce the chances of being bitten Credit: AP/FOTOLIA

Aedes mosquitoes bite during the day as well as at night (with mid-morning and late afternoon their prime feeding time), therefore it is important to reduce numbers of bites where possible, especially if below or around 2,000m above sea level:

Cover up

Use plenty of DEET-based insect repellent

Apply repellent to skin and clothing

Use room sprays and plug-in mosquito killers

Use mosquito nets at night

A Which? survey found that many popular high-street insect repellents provided ineffective protection against the Aedes aegypti mosquito. The consumer association tested 19 brands of repellent, and found that only six offered 100 per cent protection.

The best performers included Lifesystems Expedition Plus 50+, Tesco Insect Protection Max Strength, Sainsbury’s Extra Strength Insect Repellent and Superdrug Buzz Off, all of which include the ingredient DEET.

Some consumers avoid DEET-containing products because the chemical has a strong smell and can irritate skin.

Weak performers included Lifesystems Natural Plus 30+ and Incognito Anti-Mosquito, although Howard Carter, founder of Incognito, said the Which? test results were "unreliable".

Useful links:

NATHNAC: travelhealthpro.org.uk

CDC: cdc.gov/zika/index.html

ECDC: ecdc.europa.eu/en/healthtopics/zika

WHO: who.int/mediacentre/factsheets/zika/en/

Foreign Office: gov.uk/guidance/zika-virus