Heavy rainfall and heat swamp Sri Lanka’s anti-dengue drive

Colombo (Thomson Reuters Foundation): High temperatures and unseasonal rains have combined to effectively scuttle Sri Lanka’s efforts to curb dengue, experts say.

The island is facing yet another outbreak this summer, with infections more than doubling in June to 3,421 cases, up from 1,477 cases during the same period in 2015.

The epidemiology unit of the Ministry of Health said that 23,000 infections had been reported countrywide up to the second week of July. In comparison only 29,000 cases were reported for the whole of 2015.

The outbreak follows heavy rains in May that left large parts of the island inundated for days. Just before the rains, the country witnessed an extended period of above-average temperatures, with the Meteorology Department confirming some areas were experiencing temperatures between 2 to 3 degrees Celsius higher than usual.

Changing weather patterns, as a result of climate change, are likely to make the battle to control dengue increasingly difficult in years to come, officials say.

“Changing rain patterns contribute to extend the period of dengue virus transmission due to more (mosquito) breeding. Temperature also plays a pivotal role by contributing to high level of (mosquito) activity,” said Faseeha Noordeen, a senior lecturer and virologist at the Faculty of Medicine at the University of Peradeniya.

“These collectively contribute to extended periods of transmission and outbreaks,” she said.

The capital Colombo and the surrounding Western Province have been the hardest hit areas, with close to 50% of the infections reported from the province, which is also the country’s most densely populated area.

Of the 29,000 infections reported so far, 7,400 have been from Colombo.

During the May floods, large areas of Colombo were underwater for several days and, prior to the rains, the district also recorded high temperatures.

“It is obvious that changing rain patterns contribute to spread and expansion of dengue in the island,” Noordeen said.

Clean-up push

As during past outbreaks, government authorities have heightened eradication and awareness programs.

Members of the armed forces have been tasked with clean up operations and public officials in high-risk areas in Colombo have warned of strict action, including legal cases, against those who permit standing water on their property, which allows mosquitoes to breed.

“People are negligent, and allow breeding grounds to remain without cleaning them up. They need to be much more aware of the mosquitoes spreading soon after rains,” said Paba Palihawadana, the head of the Health Ministry’s epidemiology unit.

Over five days in late June, over 36,000 people in Colombo alone were warned to clean up their properties. Of 67,055 properties inspected in the city during that period, 16,565 were found to be high-risk areas for mosquito breeding.

“Colombo is the most vulnerable area,” said Hasitha Tissera, coordinator of the National Dengue Control Programme.

Noordeen said that it was difficult to control the spread of dengue since the eggs of dengue-carrying mosquitoes survive even in the smallest of water sources.

“The battle will be a tough one for a tropical island that is battling with changing weather patterns resulting in extended heavy rains and floods,” she said.

She said that instead of reacting to outbreaks, health authorities should study conditions that led to previous epidemics and devise a concerted plan that builds awareness and cleans up breeding areas throughout the year.

“Regular community clean-ups are a must in every village and township,” she said. And unless a comprehensive control plan “is put together and sustained, it’s going to be tough.”