The global climate problem has reached the high Himalayas in Nepal in the form of a mosquito. That is, two types of mosquitoes: the tiger mosquito (Aedes albopictus) and the yellow fever mosquito (Aedes aegypti). The mosquitoes can transmit the dengue virus, which causes dengue fever.
In 2004, the first patient was diagnosed with dengue fever in Nepal. Things have gone fast since then. In 2006, 2010, 2013, 2017, 2019, 2022 and 2023, the country experienced outbreaks of the originally tropical infectious disease, with tens of thousands of sick people and dozens of deaths every year. The first cases of illness were limited to the lowlands and areas around the capital Kathmandu. But it has continued to spread to almost all districts of Nepal.
The Italian photographer Yuri Segalerba works a lot in Latin America and several years ago tried to make a report on the consequences of climate change in the Andes. Tropical mosquitoes would penetrate further and further into the high mountains. However, it turned out that little or no scientific research had been done on this, and that meant that the trail was a bit of a dead end.
Photos Yuri Segalerba
However, Segalerba heard from Yolden Kwan, a researcher friend at the Freie Universität Berlin, that in Nepal studies are underway in this area. So he packed his things and traveled to an area unknown to him. In Nepal he witnessed that originally tropical mosquitoes can now reproduce in the high mountains. Chandannath village in Jumla district, located at an altitude of 2,438 metres, was the highest point where researchers from the Nepal Health Research Council Aedesmosquitoes and their larvae. Year after year, the limit at which disease spreaders can survive continues to rise.
The mosquitoes need a minimum temperature of about 15 degrees Celsius to survive and reproduce. Due to warming, winters higher in the mountains have also become milder, causing the Aedesmosquitoes could spread. According to climate models, the average temperature in Nepal will increase by another 0.5 to 2 degrees by 2030. The changes are relatively large, especially in the highlands.
Mosquito season in Nepal typically begins after the monsoon, when excess rainwater provides an ideal breeding ground for mosquito larvae. In higher altitudes the mosquito season is short, but it is still enough to infect people with dengue fever. In 2024, Nepal counted almost 42,000 infections, from which 15 people died. The year before, during a major outbreak, there were more than 54,000 infections, with 88 deaths. This is the tip of the iceberg, because most infections are mild and can be combated with paracetamol.
Photos Yuri Segalerba
The risk of dengue is often underestimated in the high-altitude areas of Nepal, says Segalerba. This is because the disease is relatively new and people do not expect that they could become infected in the mountains. Alarmed by the results of the study, the government has started local awareness campaigns, focusing on spraying insecticides and checking stagnant water near houses, where mosquitoes can breed.
There is currently no medicine or vaccine against dengue fever. People who become seriously ill need hospital treatment, but during an epidemic the influx can become so great that hospitals become overloaded. Good hospital care is lacking in remote areas. Traditional healers try to help people with ‘sowa rigpa’. Patients are prescribed a herbal preparation that is tailored to the person rather than the disease.
