Nepal | November 17, 2019

Climate change triggers dengue in unsuspecting areas

‘Virus is replicating throughout the year with rising temperature’

Sabitri Dhakal

Kathmandu, August 6

Dengue, a mosquito-borne disease generally found in warmer Tarai region, has started to spread in unsuspecting hilly districts of Rukum, Dailekh, Achham and Kalikot, thanks to climate change.

Nepal recorded 3,200 dengue cases from May 13 to August 6. Although authorities could not provide data of dengue cases reported in the same period a year ago, they said the number of people infected by the disease had shot up this year largely because of outbreak of the disease in Dharan.

After Dharan, dengue outbreak was reported in Mahottari, Pokhara and Hetauda, according to Epidemiology and Disease Control Division, which recorded 302 dengue cases in fiscal year 2014-15, 134 cases in 2015-16, 1,527 cases in 2016-17 and 2,111 cases in 2017-18.

Climate change in the Hindu Kush Himalayan Region is the major cause for the growing number of dengue cases, said Meghanath Dhimal, chief research officer at the Nepal Health Research Council.

A rise in temperature and change in rainfall pattern provide a breeding ground for dengue. The dengue virus replicates in temperature above 18 degrees Celsius. As the temperature exceeds 18 degrees Celsius in many areas of the country, risk of virus replication has gone up.

“Virus is replicating throughout the year with the rising temperature, triggering dengue outbreaks in hilly and mountainous regions,” said Dhimal.

Change in rainfall pattern due to climate change is another reason for rise in dengue cases. In areas affected by droughts, people are collecting rainwater in vessels and they do not cover these vessels, providing a favourable environment for mosquitoes to breed, said Dhimal. “This was one of the reasons for dengue outbreak in Dharan.”

Mosquitoes also breed in rainwater harvesting tanks. To prevent such breeding, rainwater harvesting tanks should be completely covered. Mosquitoes also lay eggs in the water in air conditioners. “We need to be careful about this too,” said Dhimal.

Areas with high migration rate are generally prone to dengue outbreaks. Kathmandu is one of those places in Nepal which sees movement of a large number of people from across the country and abroad.

Kathmandu reported five dengue cases in 2016, which fell to one in 2017 but shot up to 16 in 2018. Kathmandu has not reported any dengue case this year.

“But we need to be careful,” Ghanashyam Pokharel, senior public health administrator at EDCD said, adding, “Kathmandu’s temperature is favourable for growth of mosquitoes.”

Aedes aegypti mosquito is the primary source of dengue. The virus is transmitted to humans through the bite of infected female mosquitoes. It generally bites early in the morning and in the evening, before dusk.

Severe dengue is potentially a deadly complication due to plasma leaking, fluid accumulation, and respiratory distress. There are chances of mortality if there is co-infection of other bacteria in dengue patients. Temperature rise is giving mosquitoes a favourable environment to breed, said Anup Bastola, consultant tropical medicine physician at Sukraraj Tropical and Infectious Disease Hospital.

Preventive measures

  • Search, destroy mosquitoes and their breeding areas
  • Keep environment clean
  • Use nets and apply mosquito repellents
  • Wear long sleeves and pants to cover arms and legs
  • Remove water from flower/plant pots and plates
  • Change water in vases/bowls
  • Remove water from tyres
  • Take medicines only on doctor’s advice

A version of this article appears in print on August 07, 2019 of The Himalayan Times.

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