Zika virus: Old-fashioned methods may prove valuable in the fight against a poorly understood disease

Couples in danger zones would be wise to put off having a baby; long sleeves should be worn, and repellents applied liberally

Across Brazil hundreds of infants have been born with microcephaly. The World Health Organization has now declared the Zika virus a "public health emergency of international concern" (Getty)

What little is known about the Zika virus makes a firm case for the strongest possible international response. Most shocking are the deformities it appears to cause in newborn babies. Across Brazil, where the virus is flourishing, hundreds of infants have been born with microcephaly, a condition that leaves them with abnormally small heads, and likely to suffer from brain damage. Parents across the Americas – and now further afield – live in fear for the health of their future children.

So it is to be welcomed that the World Health Organisation announced a public health emergency, the first such pronouncement since the spread of Ebola caught governments by surprise in 2014. Zika is dangerous, unexpected and crossing borders, with experts of the view it could infect up to four million people, reaching Asia, sub-Saharan Africa, the USA and potentially Europe. The declaration of a public health emergency will increase international co-operation and focus on the virus. It can carry political and economic costs, too: advice from the WHO to avoid travel to parts of West Africa during the Ebola crisis helped knock $1.6bn off the growth of countries at the centre of the outbreak. Though Brazilians may bristle at being cut off, such costs must be borne.

The simplest response should involve a surge in old-fashioned methods of mosquito control. The virus is carried by a mosquito species, Aedes aegypti, which can breed in soda cans, or even the pools of water collected in a plant pot. Unlike the species that carries the malaria virus, it looks for food during the day, so bed nets are no help. Vaccines are perhaps a decade off. Instead, households in at-risk zones should be advised to remove all standing water, and provided with DDT. It was this chemical that lay at the heart of successful purges against malaria and dengue-carrying mosquitos in Latin America between the 1930s and early 1960s. The risks are known: DDT is a powerful pesticide, and should not be dumped outside, as it was previously. But as the director of vector-borne diseases at America’s Centres for Disease Control and Prevention points out, it carries next to no risk used on walls inside homes. The Brazilian government has mobilised its armed forces to go door-to-door spreading information and insecticides. Other at-risk countries should follow suit.

In addition, it is sensible to turn attention not just to killing Zika-carrying mosquitoes, but preventing their being born. A British company has engineered a modified mosquito that sterilises the offspring of those it mates with: these creatures are already being released in Brazil, and have been shown to reduce the size of local populations dramatically. Some argue for an attempt to eradicate the mosquito altogether: yet the unintended ecological consequences of such a drive present too great a risk. Bats, turtles and fish feed on mosquito larvae.

For now, as the international response kicks into gear, personal responsibility comes to the fore – just as it did during the Ebola crisis, in which West Africans were advised to change their greeting and burial habits. Couples in danger zones would be wise to put off having a baby; long sleeves should be worn, and repellents applied liberally. Meanwhile, the coming burst of research into Zika must be matched by governmental efforts to inform citizens, spread insecticides, and drain the swamps Aedes aegypti breeds in. Such methods worked in the past, and can work again today.