This tropical disease has become a major new health threat in Nepal

When Rambhadur Bishwakarma began running a high fever in October, he at first wasn't overly concerned.

"I thought the symptoms were of simple flu or usual fever," he said. "But things started getting worse gradually."

After a week with no relief, he went to Fewa City Hospital for a blood test and came up with an unexpected diagnosis: dengue fever.

"None of our family members had been diagnosed with this disease until now and I had never heard about its incidence in our neighborhood," Bishwakarma said.

But mosquito-carried dengue fever - usually thought of as a tropical disease - is gaining ground in temperate western Nepal as climate change brings warmer temperatures and changing weather conditions.

Yam Baral, a vector control inspector for the public health office in Kaski District, which includes Pokhara, a gateway to the Himalaya Annapurna Circuit, said his office saw two cases of dengue in 2017.

This year, so far, there have been more than 150.

"In the past years the Aedes mosquito couldn't survive the cooler temperatures. But increases in temperature and precipitation in recent years means a single infection can cause an epidemic," Baral warned.

He said the migration of people from tropical areas to the district could have played a role in seeding the disease. But more warmth and rainfall, in an already wet district, were the reasons it was quickly expanding, he said.

Purna Prasad Devkota, a weather officer at the regional agricultural research station in Lumle, said average temperature is now rising every year in Kaski.

"Mosquitoes are proliferating in those districts that never saw any traces of these insects before," Baral said.

Even districts well north of Kaski - including mountainous Mustang and Manang, which once saw snowfall even in summer - are now seeing mosquitoes, he said.

And the mosquitoes are causing other problems besides dengue in Kaski, he said, including cases of malaria and encephalitis.

Last year the district saw 15 cases of malaria, with the numbers "expected to rise far beyond (that) this year," he said.

Pokhara residents say they're worried that dengue may soon become a regular problem in the city as cases spread.

"Three of our neighbors have already been diagnosed with the disease and I fear we will catch the disease" said Bishnu Parsad Bhandari, who owns a shop in Pokhara-8, the most affected part of the district.

"Winter is already here but mosquitoes are still around," he said.

Sramika Rijal, an environmental science professor at the district's Agriculture and Forestry University, puts the blame for the changes squarely on climate change.

"Global warming has aided in expanding the habitat of mosquitoes, as many cooler areas are getting warmer," she said.

Urban areas such as Pokhara are particularly at risk as fewer mosquito predators, from birds to bats, live in cities, and people live closer to each other, she said.

Warmer temperatures also increase how frequently the mosquitoes that are around bite, she said.

The district government has launched a range of initiatives to control the spread of mosquito-borne diseases, from awareness campaigns to efforts to kill mosquito larvae, Baral said.

The district is also trying to speed diagnosis of mosquito-carried diseases, and carefully monitor the number of hospital cases, he said.

But "the numbers of cases are still on the rise", he said.