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.
There are current reports of cases of the virus in at least 23 countries – almost all of them 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.
• Pregnant women told not to travel to Brazil
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 and Haiti.
Luiza Arruda was born with a rare condition, known as microcephaly. Luiza’s mother Angelica Pereira was infected with the Zika virus, and Brazilian health authorities are convinced that Luiza’s condition is related to the Zika virus Photo: AP
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.”
• Zika virus outbreak will spread through the Americas, says World Health Organisation
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.
Where local transmission of Zika virus has been found – map
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.
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.
A researcher looks at Aedes aegypti mosquitoes at the Institute of Biomedical Sciences of the Sao Paulo University, who are training locals to combat Zika
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.
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.
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 killers
• Use mosquito nets at night