Let us spray

PANDEMICS make for good horror films. Few things are scarier than a dangerous, incurable new disease that spreads quickly. And globalisation means that plagues can travel far, wide and terrifyingly fast. Diseases such as HIV/AIDS, SARS, West Nile virus and Ebola fever were born in places as varied as African jungles and Chinese poultry markets. Then they broke out to spread panic around the world.

The newest horror is Zika (see article). This mosquito-borne virus, which originated in Africa, was spotted in Brazil last year. It is now moving across Latin America and the Caribbean, with cases in more than 20 countries. Originally, it was thought to cause little worse than a rash and fever. Now, propelling the disease into the realm of nightmares, doctors suspect that when pregnant women catch it, their babies may be permanently damaged. Zika is the prime suspect for a sharp increase in the number of babies with microcephaly in Brazil. Children are born with abnormally small heads and are likely to be brain-damaged. They may suffer severe learning difficulties, seizures and other problems. Many will die young.

Scientists are trying to confirm the link between Zika and microcephaly. Some suspect that the virus may also occasionally cause serious damage to nerves and the immune system in infected adults. Though a mosquito bite is the main way to catch it, there are fears that it can also be transmitted sexually. Are the risks so high that countries lucky enough to be free of it should advise their citizens to stay away from those known to have it? Will it sweep through entire populations, creating herd immunity? And if so, should women try to avoid getting pregnant until that happens, as governments in some Latin American countries have advised?

Zika has no cure and a vaccine will not be available for at least a decade. But that is no cause for despair—nor for governments to scare women into not having babies. Two things are known for certain. The first is that the main, possibly only, transmission route is via mosquitoes, which pick up the virus from infected people and pass it on when the pests next take a meal. The second is how to cut the number of mosquitoes—and preferably eradicate them.

The idea of fighting mosquitoes has a long history. Aedes aegypti, the species that carries not only Zika but dengue, chikungunya and yellow fever, was almost eliminated from much of South America by the early 1960s, after a long anti-dengue campaign. The insects were killed with frequent fumigation. Health workers visited households to urge people to mop up standing water, where mosquitoes breed. But some countries slackened their efforts too soon. After the number of cases fell, politicians’ attention waned. And the mosquitoes returned in their buzzing billions.

Biting back

That campaign was led by the American regional branch of the World Health Organisation. It now needs to rally governments for a new push. Brazil is mobilising its armed forces for a nationwide door-to-door information campaign; other affected countries should do likewise. In poorer countries, donors could pay for ad campaigns, new health workers, insect repellents, insecticides and bed nets. If reservoirs of the virus are not to remain, ready to re-emerge, action is needed across the territory where Zika is at large and also in places, such as the subtropical parts of the United States on the Gulf of Mexico, where it is sure soon to arrive.

Research into novel ways to kill mosquitoes also deserves more funding. Genetic modification, which produces mosquitoes that are sterile but still attractive to other mosquitoes, shows promise. A trial in Brazil suggests that releasing swarms of modified insects can reduce the unmodified population in months.

All this will be pricey. But it would bring not one, but several, dread diseases under control. Aedes aegypti does not carry malaria, but the methods used to kill it will also kill Anopheles, which does. The moment has come again to take the fight to the mosquitoes—and this time to finish the job.