Nepal is experiencing a worrying spread of dengue fever higher up into Himalayan valleys where the mosquito-borne disease was unknown until a few years ago. 

In 2025, 15 of the country’s 16 high-altitude districts reported infections, marking an unprecedented ascent of the vector and virus over 2,400m. A Tribhuvan University study has confirmed the presence of Aedes aegypti and Aedes albopictus mosquitoes and their larvae, in Jumla (2,438m). 

In Solu Khumbu district, no systematic scientific research has yet been conducted, but dengue cases have been reported in patients without travel history, suggesting the presence of vectors at the base of Mt Everest as well.

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Chandannath Municipality, 2,438m, in Jumla is the highest that the dengue-carrying Aedes aegypti and Aedes albopictus mosquitos have been detected.

Until recently, Aedes mosquitoes had only been detected up to 2,100m. Over the past two years, however, dengue has spread across almost the entire country, affecting 76 of Nepal’s 77 districts in 2024 and 2025. 

The Epidemiology and Disease Control Division data shows 42,647 people were infected since January 2024, 19 of whom died. But the number of unreported infections is probably much higher.

Scientists from the Nepal Health Research Council (NHRC), in collaboration with the Institute of Tropical Medicine in Antwerp, collected mosquito samples to analyse them and examine how they are adapting to warmer temperatures and  resistance to insecticides. The specimens are carefully observed, photographed, and catalogued, allowing researchers to document patterns of survival, distribution, and resistance. 

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Santos Pandey, Pratima Bhandari and Sangita Chand examine dengue vector mosquitoes under a microscope at the NHRC laboratory in Kathmandu.The entomology unit uses stereomicroscopes to identify the subtle differences between the Aedes aegypti and Aedes albopictus mosquitos. Differences in thoracic markings in the insects helps determine disease risk and guide surveillance and control strategies for dengue and other mosquito-borne illnesses.
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A female Aedes aegypti mosquito under a microscope. Studying both larvae and adults to detect colour or shape variations may indicate insecticide resistance or adaptation to different altitudes. Each specimen is photographed for analysis and digital archiving.
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Sushila Devi Shah, 38, at the Sukraraj Tropical and Infectious Disease Hospital last year. She suffered severe muscle and eye pain, headache, and fever, the main symptoms of dengue. Complications can be serious if untreated.
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Shiva Rajbanshi of the NHRC captures mosquitos and larvae in a breeding site. This work helps assess mosquito distribution and guides prevention efforts in areas where rising temperatures allow mosquitoes to survive and proliferate.

Experts attribute the spread of dengue into Nepal’s mountainous regions primarily to global warming, which creates more favourable conditions for mosquito survival and reproduction, even in areas once considered at low or no risk. The dengue-carrying mosquito mainly bites in the early mornings and evenings when people are out and about.

Increased mobility within Nepal with the spreading road network and greater international connectivity have also contributed to circulating the virus. As a result, dengue is reaching Himalayan communities with poor healthcare facilities. 

In these remote and hard-to-access areas, many residents continue to rely on traditional Tibetan medicine, known as Sowa Rigpa, practiced by traditional Amchi healers who enjoy strong cultural trust and have long served as key healthcare providers within local communities.

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Jomsom at 2,743m has seen erratic and extreme weather patterns with dry months becoming drier, and the monsoon seeing intense storms in this arid region. Average temperatures are rising, creating favourable conditions for mosquito-borne diseases. In 2025, nine cases of dengue were reported in Mustang district.
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Khedup Loden Gurung checks a patient’s pulse in a clinic in Jomsom at 2,743m last year. Amchi are traditional Tibetan healers trained in Sowa Rigpa. Diagnosis is based on pulse reading (nad-par), visual examination of urine and tongue, and dialogue with the patient. Because Sowa Rigpa focuses on the individual’s overall energetic state rather than on specific pathogens, there is no direct equivalent to the biomedical concept of ‘dengue’.
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Handmade Sowa Rigpa herbal remedies crafted using traditional methods. After drying and processing, medicinal plants are ground by hand and combined according to precise traditional formulas. The mixtures are prepared into powders, pills, or pastes using simple tools and manual techniques passed down through generations. Before distribution, the medicines are ritually blessed.
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Khedup Loden Gurung treats a young patient in a clinic in Jomsom. Rooted in Buddhist monastic culture, many amchis approach healing as an act of compassion and service, practicing medicine as a vocation rather than a commercial activity for profit.

Practiced across the Himalayan region and influenced by Indian Ayurveda and Buddhist philosophy, Sowa Rigpa combines clinical observation, herbal remedies, and a holistic view of health, in which body, mind, environment, and spiritual dimensions are deeply interconnected.

To curb the spread of dengue, Nepal’s health authorities have a two-pronged prevention and awareness. Strategy involves using insect repellents and mosquito nets, proper household environmental management, and community campaigns to eliminate stagnant water and strengthen vector surveillance. 

The goal is to improve the capacity of communities to respond promptly to emerging health threats in a territory increasingly exposed to the impacts of climate change. Vaccines against the two main strains of dengue exist, but they are expensive and have side effects. Prevention and vector management are therefore the primary strategies available to combat dengue.

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Solukhumbu District Hospital at Phaplu, 2,413m. Hospitals in these highland areas work under challenging conditions, managing a range of health needs with the resources at hand.
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Bijay Singh Kushwaha collects sample blood from Nara Maya Khatri, 87, admitted with suspected dengue for a rapid diagnostic test. In recent years, such cases have become more familiar in the region, and the hospital is increasingly accustomed to managing them.
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Sunita Baral and her team work in the NHRC laboratory.
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Pramod Shrestha installing a data logger at an NHRC mosquito breeding site last year to track temperature and humidity in real time — conditions that determine the mosquito life cycle, influencing development, survival, and egg hatching. Certain species including Aedes aegypti and Aedes albopictus, prosper only within narrow climatic ranges, so these measurements help understand how mosquitos adapt to climate change.
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Fog in Pokhara Valley moving up the Annapurnas, just as dengue-carrying mosquitoes move up the mountains. Rising temperatures, coupled with unseasonal pre-monsoon downpours provide ideal breeding conditions for dengue-carrying mosquitos. These conditions enable vectors to survive at increasingly higher altitudes. Public awareness and prevention remain key factors to limit the spread of the dengue virus.

©2026YuriSegalerba

©YuriSegalerba

©YuriSegalerba©YuriSegalerba

Mountain Mosquitos

mosquitos climb up the mountains

Rising global temperatures have allowed mosquitos to thrive higher than ever before in the Himalaya. This means an increase in the distribution and intensity of vector-borne diseases like dengue, malaria, encephalitis and zika.

Mosquitos breed all year round at lower elevations, but higher up the invasive mosquitos are seasonal and exist alongside native species. In Nepal, dengue-carrying mosquitos were only found below 2,000m in summer. But the vectors and their larvae were recently detected at nearly 2,500m in Jumla, and there is evidence it has also spread to Solukhumbu.

Out of Nepal’s 77 districts, last year dengue patients were found in 75. Factors are: climate change, urbanisation, poor awareness and greater domestic and international connectivity.