What is the mosquito-borne disease Sri Lanka is using drones to fight?

Image source, Getty Images Image caption, The virus, which is spread to humans through mosquitoes, is common in tropical climates By Kelly Ng  and  Sampath Dissanayake , BBC Sinhala Published 11 minutes ago Battling its worst dengue outbreak in nearly a decade, Sri Lanka has deployed military drones to scan for stagnant pools of water on rooftops and other mosquito-breeding sites. The virus has killed 56 people and infected more than 77,000 others in the South Asian nation this year, with more than a quarter of them reported in July alone. Dengue fever, which is spread to humans through mosquitoes, is common in tropical climates. But as temperatures rise worldwide, these disease-carrying mosquitos are now moving into new areas, including Europe and the Mediterranean. According to the WHO, the number of global reported cases surged from around 500,000 in the year 2000 to 14.4 million in 2024. What is dengue fever and what are its symptoms? Dengue is a viral fever caused by the dengue virus, which is transmitted to humans through the bite of infected Aedes mosquitoes. These mosquitoes breed in stagnant water like pails, vases and flowerpot plates. They are most active during daylight hours and usually bite just after sunrise and around sunset. Many people who get dengue do not develop symptoms. For those who do, the most common symptoms include high fever, headache, muscle and joint pains, nausea and rashes. These usually resolve within a week or two. In severe cases, however, dengue can lead to internal bleeding or even death. Those who get infected a second time are at a greater risk of severe dengue. There are four strains of the dengue virus and healing from one would only protect you from that specific strain, says Kapila Kannangara, director of Sri Lanka's Dengue Control Unit. "That immunity does not extend to other strains of the virus. That means someone infected by one strain of the virus could still get dengue again if infected by a mosquito carrying another strain." "This could mean that they get an even more serious infection," he tells BBC Sinhala. As there is no universal vaccine for dengue, treatment often involves managing pain with medication such as paracetamol. Patients who develop severe symptoms would often require careful monitoring in hospital, as complications can be lethal. What's the situation in Sri Lanka? Sri Lanka's health authorities attribute the surge in dengue infections to a cyclone that tore through the island last December, scattering debris that have turned into new breeding grounds for mosquitoes. The government has tasked the military to use drones to scan the rooftops of homes, schools and construction sites, and deployed police officers to go to people's homes for physical inspections, Nearly 11,000 mosquito breeding sites have been cleared so far this month, while more than 4,000 premises fined for harbouring those sites. Although infections have been reported across the country, they tend to concentrate