Zika virus: Medical advices for travellers

What is the Zika virus?

Zika is a newly-emerging virus that began ringing public health alarm bells in May 2015, in Brazil, and is now spreading rapidly. This follows a dramatic increase in recent months and years of two other viral infections that cause similar illnesses, chikungunya and dengue fever.

What is the advice for British travellers?

There are current reports of cases of the virus in at least 23 countries, including most recently in Thailand. The tour operator Thomas Cook has said it would contact airlines to request changes for customers who are pregnant who no longer wish to travel to Thailand.

Nearly  all of the countries where cases have been reported are in tropical South America, extending into Central America and the Caribbean. But the true extent is not known with certainty, since not all of the affected countries have necessarily been conducting surveillance. Past cases have occurred in Africa, Asia and the Pacific.

Concern has spread far beyond the affected areas however to Europe and North America, where dozens of cases have been identified among people returning from holidays or business abroad.

Credit: Getty Images

The Foreign Office currently advises British travellers to take precautions if visiting the following countries: Dominican Republic, Brazil, Venezuela, Colombia, Guadeloupe¸ Panama, Guyana, Suriname, Honduras, Guatemala, Mexico, Martinique, French Guiana, Paraguay, Bolivia, Ecuador, El Salvador, Barbados, Puerto Rico, Haiti, Jamaica and Thailand.

Its advice for travellers states that cases of Zika virus have been reported in 2015 and 2016; "you should follow the advice of the National Travel Health Network and Centre, particularly if you’re pregnant or planning to become pregnant, and seek advice from a health professional."

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.

What are its effects?

Until very recently 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.

Credit: WHO PAHO

A recent spate of birth defects in northeast Brazil has now been linked to exposure of the fetus to the Zika virus. The defects are especially unpleasant and alarming. The exact mechanism, plus the likely role of additional risk factors, are not yet known, but the implications are so serious that a massive public health investigation is now under way.

The defects are anencephaly – failure of brain development – which is lethal at birth, and microcephaly – reduced brain development – which generally leads to lasting impairment. The risk is potentially present at all stages of pregnancy.

People infected with Zika virus seem also to be at increased risk of a rare neurological condition called Guillain Barré syndrome (also known as GBS), believed to be triggered by an immune reaction. Nerve damage can lead to muscle weakness, paralysis and other neurological symptoms. Despite the increase in cases, this still remains a rare occurrence.

What are the implications for travellers?

Until more is known, public health authorities are advising pregnant women to be extremely cautious about travelling to countries where Zika is present, with careful anti-mosquito precautions as an absolute minimum. With the Olympics due to take place in Rio in August this outbreak could hardly have come at a worse time.

More alarming still is the fact that Zika is likely to spread much further, since Aedes mosquitoes are widely present in hot countries.

What preventive measures are available?

There is no vaccine, but rapid development of a new vaccine might ultimately be the best prospect for controlling Zika, and the recent global response to the Ebola outbreak may help facilitate this.

Public health measures are vital to keep Aedes mosquito populations under control, but this can be notoriously difficult to do.

Aedes mosquitoes bite during the day as well as at night: therefore it is important to reduce numbers of bites to the extent possible:

• Cover up
• Use plenty of DEET-based insect repellent
• Apply repellent to skin and clothing
• Use room sprays and plug-in mosquito killersUse 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".

About Zika virus

The most common symptoms of the Zika disease are fever, rash, joint pain, and conjunctivitis (red eyes), usually lasting from several days to a week, and most patients don't need hospitalisation. However the outbreak in Brazil has led to instances of Guillain-Barre syndrome and pregnant women giving birth to babies with birth defects

A mosquito viewed under a microscope Credit: Fotolia/AP

How it spreads

• Through mosquitoes, which mostly spread the virus during the day
• Through sexual transmission
• Mosquitoes also spread dengue and chikungunya viruses
• There is no vaccine

How to prevent it

• Avoid getting mosquito bites by using insect repellants, and wearing long-sleeved shirts and trousers
• Use air conditioning and/or a window screen to keep mosquitoes outside
• Sleep under a mosquito bed net
• Reduce the number of mosquitoes by emptying standing water from containers such as flowerpots or bucket

Source: Centers for Disease Control and Prevention
Additional reporting by Lizzie Porter - Telegraph.co.uk