Dengue fever is the most common febrile illness in the world, with more than 5 million cases reported to the WHO in 2025. It is a disease of the tropics and subtropics, caused by any of four serotypes of a virus transmitted by day-biting Aedes mosquitoes. Nepal had a large dengue outbreak in 2022, with smaller outbreaks in the years since.
The Aedes mosquitoes that carry dengue are mostly confined to urban areas, where they breed in the relatively clean water found in storage containers, discarded tyres and tin cans. Once bitten by an infective mosquito, a person becomes sick within two to eight days.
Symptoms
Sudden high fever, pain behind the eyes, headache, backache, joint and muscle aches and marked fatigue — often with a rash that looks like a red flush on the back, chest and abdomen. The fever returns to normal within a week.
A small number of patients develop dengue with warning signs or severe dengue and need to be hospitalized for supportive treatment. There is no specific treatment, and most people recover on their own.
Warning signs:
- Abdominal pain
- Persistent vomiting (more than three episodes in 12 hours)
- Fluid accumulation, such as pleural effusion or ascites
- Mucosal bleeding — gums, eyes, nose, vaginal bleeding, coughing up blood or blood in the urine
- Lethargy or restlessness
Severe dengue (WHO criteria): fluid in the lungs with respiratory distress, severe bleeding, or severe organ impairment such as hepatitis, impaired consciousness or heart impairment.
Prevention
With no specific treatment, the focus is prevention — above all, avoiding mosquito bites:
- Cover up where practical.
- Use insect repellent: DEET 30% or picaridin 20%. Odomos cream, available in Nepal and India, can be equally effective.
- Stay in screened or air-conditioned accommodation.
Vaccines
The dengue vaccine currently available is Qdenga, which can be given to anyone aged 4 and over without first confirming a previous dengue infection. It is approved in the European Union, the UK and several other countries, and received WHO prequalification in May 2024.
Qdenga is not yet licensed in Nepal.