The Epidemiology and Disease Control Division has alerted 15 local levels across the country, including the Kathmandu Metropolitan City, about the risk of a massive dengue surge after more than five cases were reported last month.

Officials say they have asked the concerned local governments to launch a dengue search and destroy drive and make people aware of the risk, amid rising temperatures and pre-monsoon rainfall.

“Multiple factors, including rising temperature, pre-monsoon rainfall, and drinking water crisis, which prompts people to hoard water in open tanks, increase the risk of dengue surge,” said Dr Gokarna Dahal, chief of Vector Control Section at the division. “We have written letters to 15 local levels, including the Kathmandu Metropolitan City, which recorded more than five cases of infection in March and have also alerted others about the risks.”

Dengue is a viral disease transmitted by female Aedes aegypti and Aedes albopictus mosquitoes. According to the World Health Organisation, the same vectors also transmit chikungunya, yellow fever, and the Zika virus.

Dengue continues to spread through Nepal even during the winter months, as 149 people were infected in January, 155 in February and 152 in March. The number of cases reported in the same months of last year was double compared to this year’s reported cases. Data shows that 259 cases were reported in January 2025, 252 in February and 254 in March.

“Compared to last year’s data, dengue cases have declined this year,” said Dr Roshan Neupane, director at the division. “But a decline in the number of reported cases does not mean that risk has lessened. We have asked all concerned agencies to start preparation accordingly, launch search and destroy drives and inform the public about the risk of the infection.”

Officials say that the budget has already been allocated to local levels for dengue prevention programmes.

Since dengue became endemic in Nepal years ago, health authorities no longer classify new cases as outbreaks.

In 2025, at least six people died, and around 9,000 were infected with the dengue virus, which has spread to 76 out of 77 districts of the country. All mountain districts except Humla reported dengue virus infection this year. It was previously believed that dengue-spreading mosquitoes could not survive in very cold climates, and there was no risk of dengue in mountain districts. However, the division’s data show otherwise.

Experts say even though winter maximum temperatures have dropped, they remain above 15 degrees Celsius, which is warm enough for dengue mosquitoes to survive.

Multiple scientific reports, including the United Nations ‘Climate Change 2022: Impacts, Adaptation and Vulnerability’ report, state that at least six major vector-borne diseases influenced by the climate drivers have recently emerged in Nepal and are now considered endemic.

Global warming has extended the elevational distribution of Anopheles, Culex, and Aedes mosquito vectors above 2,000 metres in Nepal. Of about 460 species of Anopheles, over 100 transmit malaria. Over 950 species of Aedes spread dengue, chikungunya, Zika, yellow fever, and the West Nile virus.

Experts say reported cases likely represent only a fraction of the true scale, as around 90 percent of the infected people are asymptomatic, and many deaths and infections often go unreported.

Dengue mosquitoes breed in clean water and bite during the daytime. Uncovered water tanks and discarded objects such as plastic cups and bottles can serve as breeding grounds.

Symptoms of the disease include mild to high fever, severe muscle pain, rashes, severe headache and pain in the eyes, among other things. Doctors advise those with these symptoms to seek immediate treatment. While there is no specific cure for the disease, early detection and access to proper medical care can lower fatalities.

Many people infected with dengue show mild symptoms, which do not need any treatment or can be managed with paracetamol at home.

Nepal reported its first dengue case in a foreigner in 2004 in Chitwan district. Since then, an increasing number of dengue infections, including major outbreaks, have been reported from many districts.

The World Health Organisation says there is no specific cure for severe dengue, but early detection and access to proper medical care can save lives.