29 January 2016 09:56:28

Zika virus - new year, new health threat

Previously obscure, Zika virus has sprung into the public arena since a huge spike in the birth of babies in Brazil with microcephaly (a smaller-than-normal head linked with abnormal brain development).

It happened with Ebola, which came from nowhere and dominated the headlines for months then disappeared from the news without a trace. Now the same thing has happened with Zika virus. Previously obscure, Zika virus has sprung into the public arena since a huge spike in the birth of babies in Brazil with microcephaly (a smaller-than-normal head linked with abnormal brain development). In a country which usually sees only about 160 babies born with the condition every year, there have been 3,893 new babies born with the condition in the last three months alone. In some areas, nearly one in 100 newborns have been affected.

Like Ebola, there is no reliable treatment and no vaccine available. Like Ebola, it seems to have come from nowhere but has actually been around for decades. First identified in monkeys in Uganda in 1947, the first case of human Zika virus infection was in Nigeria in 1954. By 1977, it had moved to Pakistan, Indonesia and Malaysia and on via Polynesia in 2007 to reach Brazil in 2015. Since then, it seems, there has been no stopping it, with cases seen in Barbados, Bolivia, Colombia, the Dominican Republic, Ecuador, El Salvador, French Guiana, Guatemala, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname and Venezuela.

Mexico, in case your geography is a bit rusty, is a mere hop, skip and jump away from the USA. A study this month suggested that once the weather warms up, Zika-carrying mosquitoes could spread along parts of the east and west coasts of the US and much of the Midwest, where about 200 million people live. What's more, US has some very humid areas where the mosquito could survive all year round - and those areas are home to 23 million Americans. So it's hardly surprising that President Obama has called for urgent action to develop treatment and vaccines, in the wake of the World Health Organisation prediction that it's only a matter of time before almost all the Americas are affected.

Just for once, we should probably be grateful in the UK for our miserable weather - Public Health England has reassured worried members of the public that the mosquito responsible for transmitting Zika virus doesn't live in the UK. Nor is it found in Canada or Chile - all three countries are too cold for the mosquito to survive. But Britons do travel in their droves, and not just to the USA. In the last five years, almost 1.5 million UK residents have visited South and Central America and the Caribbean every year.

The virus is passed through the bite of the Aedes species of mosquito, which also spreads the dengue fever and chikungunya viruses. Just one case of sexual transmission in semen from human to human has been recorded, and occasionally it can be transmitted in blood.

Unless there's a chance you might be pregnant, Zika virus isn't likely to be more than a minor inconvenience. Symptoms of infection tend to happen two to seven days after being bitten, although four in five people affected don't get any symptoms at all. The other 20% are likely to suffer only mildly, with fever, rash, joint pain, or conjunctivitis lasting a few days.

However, along with the sharp spike in babies born with microcephaly, there has also been a rise in cases of Guillain-Barre syndrome, a condition of the nervous system causing muscle weakness and sometimes paralysis. So it makes sense to take precautions to avoid getting infected, even if you're not pregnant.

Public Health England is advising women who are, or might become pregnant to consider avoiding travel to any area affected by Zika virus. For other travellers, avoiding mosquito bites is key. It's important to remember, too, that unlike malaria-carrying mosquitoes, which are most active at dusk and night-time, the Aedes mosquito is active all day. That means you can't rely on mosquito nets to offer much protection at all. Suggested precautions include:

- Long sleeved shirts and trousers

- Before you travel, treating clothing with permethrin (which should never be applied direct to the skin)

- Applying sun screen before insect repellent spray

- Applying insect repellent spray every few hours (although not under clothing)

- Staying in venues with air-conditioning or door and window screens to keep mosquitos out.

Dr Sarah is unable to provide medical advice or respond directly to questions concerning your health. If you have health concerns we recommend contacting your GP.