Dengue Fever Rising in the Himalayas | NRC

Dengue Fever Reaches Higher Altitudes in the Himalayas

Driven by climate change, mosquitoes carrying dengue fever are now thriving at increasingly high elevations in Nepal, raising public health concerns in previously unaffected areas. This shift marks a significant expansion of the disease’s reach within the region.

The first case of dengue fever in Nepal was diagnosed in 2004. Since then, the country has experienced outbreaks in 2006, 2010, 2013, 2017, 2019, 2022, and 2023, resulting in tens of thousands of illnesses and dozens of deaths annually. Initially, cases were limited to the lowlands and areas surrounding the capital, Kathmandu, but the infection has now spread to nearly all districts in Nepal.

Researchers have identified two mosquito species responsible for the spread: the tiger mosquito (Aedes albopictus) and the yellow fever mosquito (Aedes aegypti). Both are capable of transmitting the dengue virus, which causes dengue fever. The findings highlight the impact of a changing climate on vector-borne disease distribution.

Recent studies conducted by the Nepal Health Research Council have found Aedes mosquitoes and their larvae at altitudes as high as 2,438 meters (7,998 feet) in the village of Chandannath, located in the Jumla district. This represents the highest point where the mosquitoes have been detected to date. The upward creep of the disease’s range is attributed to the mosquitoes’ demand for a minimum temperature of approximately 15 degrees Celsius (59 degrees Fahrenheit) to survive and reproduce, a threshold increasingly met at higher elevations due to warming temperatures.

The situation in Nepal mirrors observations made in other mountainous regions. A photographer working in Latin America previously attempted to document the effects of climate change on mosquito populations in the Andes, but found limited scientific data available at the time. This underscores the need for continued research into the effects of climate change on disease vectors.

The spread of dengue fever in the Himalayas is linked to broader trends of glacial retreat and changing water resources in the Hindu Kush Himalayan region. According to a report by the National Research Council, most glaciers in South Asia are retreating, though the consequences for the region’s water supply remain unclear. Further research is needed to understand the complex interplay between climate change, glacial melt, and the spread of infectious diseases.

The National Research Council has also assessed the impacts of climate change on water resources and security in the region, which supports over a billion people through its crucial river systems. Their findings emphasize the need for improved scientific understanding and adaptive strategies to enhance regional water security amid ongoing climate challenges.

The increasing prevalence of dengue fever at higher altitudes serves as a stark reminder of the far-reaching consequences of climate change on public health. The findings could prompt increased surveillance and preventative measures in vulnerable Himalayan communities.