Faced with one of its worst outbreaks of dengue in years, Sri Lanka is using military drones to scan rooftops and find mosquito breeding grounds to eliminate.

The island nation is at war with the insect that carries the dengue virus and has infected more than 46,000 people so far this year, nearly double the number for the same period last year, and killed 29. Hospitals are stretched to capacity with more than 500 cases a day.

The epidemic is adding strain to the already stretched resources of the country of 22 million. Sri Lanka is still struggling to emerge from years of economic devastation and recent energy shortages caused by the war in Iran, which led the country to temporarily impose a four-day work week.

Sri Lankan officials are working to avoid a repeat of 2017, when 186,000 infections and 450 deaths were recorded from dengue, a viral fever that is transmitted by the Aedes species of mosquitoes. They have said the country is particularly vulnerable after a devastating cyclone hit late last year, and there have been heavy rains since January. The southwest monsoon, which lasts from May to September, has also caused minor flooding in some areas.

“There was a lot of garbage and breeding sites in the environment after the cyclone, and it took the local government authorities a lot of time to clear them out,” said Dr. Kapila Kannangara, the head of the National Dengue Control Unit, a Health Ministry agency. After the cyclone, which caused more than 1,000 landslides, local government authorities faced monumental recovery efforts. This meant that they were slow to address pools of stagnant water, which are potential breeding sites for mosquitoes.

Already, many hospitals in dengue hot spots are at capacity, including the National Institute of Infectious Diseases — the main treatment center for epidemic diseases. Overcrowded hospitals have started allocating extra wards for dengue patients.

“If cases continue to rise, we’ll have a problem with beds,” says Dr. Kannangara.

The island on Wednesday launched a nationwide three-day dengue prevention drive focused on eliminating breeding sites for Aedes mosquitoes. This included calling in the Sri Lanka Air Force, which has been flying drones over high-rise buildings in Colombo to identify breeding sites, said Group Capt. Nalin Wewakumbara, the air force spokesman.

Once the spots are found, property owners must clear them out or face a fine.

The program began in Colombo and spread across the country, focusing on schools, homes, public institutions and abandoned properties.

In the longer term, the National Dengue Control Unit is working to expand an insect sterilization program it piloted in 2021. It is also planning to release mosquitoes that carry the Wolbachia bacteria — which can neutralize the dengue virus and is passed down to future generations — in Colombo in an effort to reduce the infected mosquito population.

In Yogyakarta, Indonesia, where Wolbachia mosquitoes were released in 2017, the incidence of dengue was reduced by over 75 percent, according to the World Mosquito Program. In North Queensland, Australia, Wolbachia mosquitoes have been regularly released since 2011. Long-term monitoring has shown that this region is essentially dengue-free now.

Sri Lanka piloted the Wolbachia method in two areas in the Colombo area from 2018 to 2021, and the authorities are working to establish a factory to breed those mosquitoes.