New and potentially controversial techniques including releasing genetically modified or irradiated mosquitoes could be deployed to combat the spread of the Zika virus, according to a statement yesterday from the World Health Organisation. Zika is a disease transmitted by the Aedes aegypti mosquito. The disease originated in Africa, but in the last decade has spread to French Polynesia in the Pacific, and to Brazil and Colombia. More than 13 countries in the Americas have reported sporadic infections. “Given the magnitude of the Zika crisis, WHO encourages affected countries and their partners to boost the use of both old and new approaches to mosquito control as the most immediate line of defence,” the WHO statement said , adding that more research was needed to evaluate the new techniques. “For genetically modified mosquitoes, the WHO Advisory Group has recommended further field trials and risk assessment to evaluate the impact of this new tool on disease transmission,” the statement said, adding that trials in the Cayman Islands have shown significant reductions in the Aedes aegypti population. The disease is relatively mild, but infection in pregnant women has been linked repeatedly with a condition in babies called microcephaly and an illness in adults called Guillain-Barré syndrome. “If these presumed associations are confirmed, the human and social consequences for the over 30 countries with recently detected Zika outbreaks will be staggering,” the statement continued. Sprays and chemical assault remain standard tactics in the fight against insect borne disease. But Aedes aegypti is a serious problem: the mosquito carries the parasite for dengue fever as well as Zika. Before Christmas, a House of Lords committee said that the UK had a “moral duty” to prosecute research on genetically modified insects and their use in disease control. “We have a number of tools in our box and one of those that is being field trialled at the moment for dengue is a GM mosquito, which is essentially to release mosquitoes so that when they mate their offspring die in the larval stage,” said Michael Bonsall, professor of mathematical biology at the University of Oxford and an adviser to the Lords committee. “That has been tested in the field. It is exactly the same mosquito that spreads Zika ... It’s not the only thing we do, it is one of the things we do.” Trials have shown releases could reduce an insect population by up to 90 per cent, he said. “But we know from disease theory that we don’t necessarily have to eradicate mosquitoes from an ecosystem to have an affect on disease dynamics. As long as we suppress the population and make it smaller, below a threshold, it will have a big impact on the disease burden.” ● This article has been amended. An earlier version said that Aedes aegpti carried the malaria parasite as well as Zika. This has been corrected.