Bibek Bhandari
The district of Dolpa is remote and high, from 1,500 meters (4,921 feet) above sea level up to more than 7,500 meters (24,606 feet). Its Himalayan peaks, the turquoise Phoksundo Lake, and arduous trekking trails draw travelers from across the world. But climate change has brought unwanted visitors—mosquitoes. And with them has come a viral infection that was previously unknown to the region.
In September 2022, locals started visiting the only government hospital in the district headquarters of Dunai with bouts of fever and body aches, recalled Akhada Upadhaya, a medical officer at Dolpa District Hospital. There were thousands of people with similar symptoms in the low-lying, hotter plains of Karnali province, where Dolpa is located, and elsewhere in the country—and they were testing positive for dengue at alarming rates that year. Dunai, a small settlement on the bank of Thuli Bheri River at about 2,000 meters (6,562 feet), also reported its first infection then.
“It was alarming,” Upadhaya, who grew up in Dolpa, told Foreign Policy. “Before, there were no mosquitoes here. But the change in weather patterns and increase in people’s mobility is raising the risk of infections like dengue—that wasn’t prevalent in the region before.”
As global temperatures rise, many high-altitude and low-income countries are on the front lines of the climate crisis. Since Nepal detected its first dengue case in an inbound traveler in 2004, only a few hundred locally transmitted infections were found until 2015. The infections then suddenly grew at almost exponential rates in 2019 and reached a record of nearly 55,000 cases in 2022, causing at least 88 deaths. Cases were also found last year in districts, including Mustang and Humla, with an average elevation of more than 3,000 meters (9,843 feet). But doctors said the actual caseload could be much higher, as many dengue patients are either asymptomatic or don’t visit hospitals for mild symptoms.
Dengue is transmitted to humans through the bites of infected female Aedes aegypti mosquitoes and is mostly found in tropical and subtropical climates. Also known as breakbone fever, the infection causes ailments from high fever to muscle and joint pains. A second-time infection with a different variant of the virus—there are four serotypes, ranging from DEN-1 to DEN-4—is likely to cause severe conditions and even death.
In June, the World Health Organization (WHO) warned that almost half of the world’s population was at risk of dengue, as cases had increased eightfold between 2000 and 2022. The uptick was attributed to climate change, people’s movement, urbanization, and sanitation issues. About 70 percent of the cases were in Asia, according to the WHO.
In warmer Southeast Asian countries, infections have been rising steadfastly: Dengue cases in Vietnam last year rose by fivefold compared with 2021, and officials said the disease was a matter of “urgent emergency” for Singapore. In Thailand, the country’s health ministry warned that infections could reach a three-year high in 2023.
In South Asia, Bangladesh is battling its worst dengue outbreak ever—the country logged about 200,000 cases and nearly 1,000 deaths so far this year. The WHO said that the current dengue surge was “unusual in terms of seasonality” and that the case fatality rate was “relatively high” compared to previous years. This year’s dengue deaths are more than the combined total of the casualties in the past 22 years, the BBC reported, citing Bangladeshi officials. As of Sunday, dengue-related deaths in Bangladesh have crossed 1,000.
But the disease is also hitting countries where it was previously unknown—and where doctors and patients may be unfamiliar with the dangers. A 2020 study said that vector-borne diseases such as dengue and chikungunya have increased sharply in the Hindu Kush Himalayan region, particularly in Afghanistan, Bangladesh, Bhutan, India, Myanmar, Nepal, and Pakistan. The infections mostly start with the onset of monsoon season around June and peak in the post-monsoon season between September and November.
Meghnath Dhimal, the chief of the research section at the government-run Nepal Health Research Council and a co-author of the 2020 study, told Foreign Policy that the dengue-carrying mosquitoes breed in stagnant water pools at temperatures ranging from a minimum of 12 degrees Celsius (53.3 degrees Fahrenheit) to a maximum of 24-25 degrees Celsius (75.2-77 degrees Fahrenheit). He said the change in monsoon patterns and rising temperatures in high altitude and hilly regions of Nepal have led to a rapid expansion of dengue.
Deepshikha Sharma, a climate and environment specialist from the International Centre for Integrated Mountain Development (ICIMOD), an intergovernmental environmental institution, said that the rate of warming in the Hindu Kush Himalayan region is amplified with elevation. Referring to an ICIMOD report, she noted that the mean temperature has increased significantly in all areas of the Hindu Kush Himalayan regions, at an average rate of 0.28 degrees Celsius per decade between 1951 and 2020.
Nepal’s average maximum temperature increased by 0.056 degrees Celsius (0.101 degrees Fahrenheit) between 1971 and 2014, with a significant rise in the high Himalayan regions, according to a study by the Department of Hydrology and Meteorology. That’s only speeding up: Kathmandu has become hotter by 1.6 degrees Celsius (2.9 degrees Fahrenheit) in the past two decades.
“The distributions of disease vectors and disease transmission are projected to shift to higher elevations,” Sharma said. “The marginalized communities in the mountains have limited access to resources and are likely to suffer the brunt of changing climate.”
The Dolpa hospital has detected dengue 20 cases so far since September 2022, Upadhaya said, and most of them were locally acquired infections, indicating that the dengue-transmitting mosquitoes were breeding in the district due to warming weather. At least two infections were detected in November of last year, which the doctor said was unusual considering temperatures were already low then. The average low temperature in Dolpa during November hovers around 3 degrees Celsius (37.4 degrees Fahrenheit).
Though the infections in Dolpa are much lower than other parts of the country, Upadhaya said that even a single case is too many in high altitude regions that are not prone to vector-borne diseases.
But it’s not just mountainous regions and countries such as Nepal that are increasingly becoming vulnerable to climate change-induced disasters and diseases. Several Latin American countries are facing a growing dengue menace this year. The United States and nations in Europe have also reported dengue and other mosquito-borne illnesses in areas where the disease was once wiped out.
Currently, only one dengue vaccine has been licensed for use and five others are being developed, two of which are in late-stage clinical trials, according to the World Health Organization. But critics argue that there hasn’t been enough momentum on the vaccine development front.
“While people in low-income countries are still at highest risk, it may be that the spread of these diseases into Europe and North America drives vaccine development, as previously unaffected populations start to see how global infectious diseases truly are,” wrote science journalist Priya Joi.
The inequalities in the health system are most visible in countries such as Nepal, where dengue overwhelmed the country’s hospitals, even in the relatively well-equipped capital city of Kathmandu, which logged the most infections nationwide in 2022. Earlier this year, the BP Koirala Institute of Health Sciences in the city of Dharan in Sunsari district, which has seen nearly half of the country’s dengue caseload so far, converted a 100-bed COVID-19 facility to treat a deluge of dengue patients.
But doctors said such efforts wouldn’t be entirely feasible in places such as Dolpa and other remote mountainous regions due to logistical challenges and limited resources. The 15-bed public hospital in Dunai, where Upadhaya works, is the largest medical facility and only major hospital in the district, which is home to nearly 43,000 people. He said the hospital lacks a full-fledged laboratory and resources to treat severe dengue patients; instead, medical workers use rapid test kits to identify positive cases. If the disease worsens, the two doctors assigned there usually refer patients to the nearest bigger hospital in Surkhet, which can be as long as an 18-hour road journey. The flight is nearly 40 minutes, weather permitting, but reaching Dolpa’s only airport in Juphal to catch a small Twin Otter aircraft takes about an hour by vehicle or a three-hour walk.
“It’s impossible to treat severe [dengue] cases here,” Upadhaya said, adding that the hospital has been fortunate that none of the infections so far have developed complications. “It’s not like in the cities—people either die or need to wait for better health services, which might take years to materialize in a place like Dolpa. So the local government must take the issue seriously.”
Nepal’s health authorities have tried public awareness campaigns to boost knowledge of the disease, including a ringtone informing callers about the precautions and symptoms, as well as when to visit a doctor. But there is a lack of coordinated effort and sometimes negligence, too.
In Kathmandu, experts said the city’s ineffective drainage and waste management system, as well as potholes and discarded tires, have allowed an unchecked explosion of dengue virus. Dhimal said that the break in rainfall creates water pools that become a breeding place for mosquitoes, and other experts noted the authorities were often slow to respond or didn’t seem to care enough. For instance, even when the health ministry called elected officials from Kathmandu Valley’s three districts to discuss dengue prevention efforts in July, only six of the 18 officials showed up.
Doctors have repeatedly warned locals about dengue, with Sher Bahadur Pun from the Sukraraj Tropical and Infectious Disease Hospital repeatedly writing in various local publications that dengue could be “becoming a more fatal virus in Nepal.” The death rate in 2022 was almost 15 times higher than in 2019, and infection numbers and deaths this year could be similar or worse without timely interventions. As of Oct. 1, dengue cases in Nepal have exceeded 34,000. The country’s health ministry said that the infection is likely to peak between August and October, during the post-monsoon season.
“Unless there’s a coordinated multisectoral response both from the government and the entire community, it will be impossible to control dengue,” Dhimal said. “If only we invest 30 minutes a day to destroy the breeding places of mosquitoes, we can significantly control dengue in the community.”
In recent years, some countries have used emerging technological innovations to control dengue, drawing on the experience of malaria-eradication in countries such as the United States. In 2019, Vietnam announced the “Dengue Model forecasting Satellite-based System” (D-MOSS), to predict dengue by incorporating satellite data, in situ observations, and seasonal climate forecasts to better issue alerts and warnings. The technology, which is deployed on standard cloud-based servers, can help predict the number of dengue fever cases on a monthly basis up to six months in advance, according to Darren Lumbroso, the technical director of the U.K.-based research and consultancy HR Wallingford, one of the partners of the Vietnam initiative.
“The unmatched spatial coverage of satellite data can help understand the dynamics of multiple environmental stressors on the health sector, especially in regions with poor or nonexistent ground monitoring,” Lumbroso told Foreign Policy. “The D-MOSS technology is one of the possible solutions for dengue in the region because it allows user groups at different levels of government to issue regular warnings of likely outbreaks of dengue fever and improve their prevention planning and disease control measures.”
Meanwhile, scientists with the World Mosquito Program are infecting dengue-transmitting mosquitoes with bacteria that effectively reduce transmission in the laboratory. Such mosquitoes have been released in a dozen countries, including Vietnam and Indonesia, and have shown a 94 percent to 97 percent drop in dengue incidence in the city of Medellín in Colombia.
But countries such as Nepal, which are just starting to experience large dengue outbreaks, haven’t been quick enough to mull over such innovations or swift interventions to prevent infections. For now, public health experts and the authorities are largely recommending the tried and tested techniques for destroying mosquito habitats, though doctors such as Upadhaya in Dolpa believe that there should be more urgency in addressing the issue at all levels of the government.
“We haven’t found dengue-transmitting mosquitoes in altitudes that are higher than Dunai, for now,” he said. “But there could be a possibility they might exist there in the future. We must act now, or it would be too late.”
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