COLOMBO (Thomson Reuters Foundation) - Eight years after the end of a bloody civil conflict, Sri Lanka is on a war footing once again. This time all available resources have been pitched against a pesky and increasingly deadly foe: the dengue-carrying mosquito.

In the first seven months of this year more than 109,000 cases of dengue infection have been reported in Sri Lanka, according to the Ministry of Health, with over 300 deaths, an all-time high.

The infection rate is more than four times the annual average recorded since 2010.

Local and international experts warn that changing rainfall patterns that bring intense but short bursts of rain, combined with a lack of measures to limit mosquito breeding areas and the possible emergence of a new strain of the dengue virus, have made the island’s densely populated urban areas high-risk zones.

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The outbreak follows heavy rains and flooding that have affected 600,000 people across 15 of Sri Lanka’s 25 districts, according to a situation report issued by the World Health Organization on July 24.

Since May, when over 400mm (15 inches) of rain fell within two days, more than 64,000 infections have been reported, the bulk from Western Province, where over a quarter of the country’s population of 20 million live.

Dengue is a mosquito-borne viral infection that in unusual cases can be fatal. WHO and Sri Lankan health authorities have warned patients to take an antigen test to detect possible dengue if they have a fever that lasts for more than a day.

There is no cure for dengue, and medical experts recommend early detection and expert care as the most effective way of overcoming an infection.

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FAST DIAGNOSIS

Ranil Peiris from Kelaniya in Western Province, whose 6-year-old son contracted dengue in June, said it was early detection that helped them.

When the boy had a persistent fever, their doctor recommended the antigen test, and based on the results Peiris’ son was admitted to the Ragama National Hospital, just north of the capital, Colombo.

“The ward was full of patients and there were more waiting to get admitted. The doctors would only admit the serious cases. But what we noticed was that the medical staff was extremely capable. They knew exactly what to do,” Peiris said.

With infections rising, the government has imposed a standard fee of 1,000 Sri Lankan rupees (around $7) for the antigen test, specifying that results should be provided within two hours to speed up medical care.

But experts say that ridding vulnerable areas of mosquitoes is as important as detecting and treating dengue cases.

Heavy rains, combined with a lack of adequate drainage, have caused a massive increase in the number of pools of stagnant water and the amount of rain-soaked waste – ideal breeding grounds for mosquitoes, said Novil Wijesekara, a consultant health official with the Sri Lanka Red Cross Society.

Wijesekara warned that, as long as the rains persist, the threat of infections remains high.

Furthermore, Wijesekara said, Red Cross crews have discovered that locations cleared during previous anti-dengue cleanup operations had once again become breeding areas because mosquito larvae had survived and become active with the rains.

“Larvae would have been dormant when there was no rain, and with the rain the dormant larvae developed into adults,” agreed Faseeha Noordeen, professor of microbiology at the state university in Peradeniya.

“More vigilance is essential during the dry season to make sure that possible breeding areas are checked and cleaned regularly, ” Noorden said.

NEW TYPE OF DENGUE

Her research has found that a new variant of the dengue virus, known as DENV-2 has become more dominant during the current outbreak.

“When the serotype shift occurred in late 2015 or early 2016 from DENV-1 to DENV-2, many in the population met this new serotype for the very first time,” said Noorden.

“The majority in the population was not immune to this new serotype. The serotype shift is the major reason for the recent outbreaks with the unprecedented number of cases.”

The Red Cross’s Wijesekara agreed that the emergence of the new variant was a factor in the growth in dengue cases.

The Sri Lankan government has launched a nationwide campaign to stem the epidemic, even co-opting the armed forces to help with cleanup operations, but experts say it’s too little too late.

They recommend that proactive eradication measures should be implemented throughout the year, not just when the number of infections increases.

Noorden said that public dengue eradication campaigns should be synchronized with the epidemic patterns that have become apparent, such as spikes in infections following heavy rains.

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She advised the government to consult weather forecasts and launch eradication measures before heavy rains and continue throughout them.

Beyond cleaning areas up, improving drainage to avoid stagnant water is also key, Wijesekara said.

The government says it is taking all possible measures to stem the epidemic.

“It is the highest priority of the government right now and no effort will spared to get rid of dengue. We will make sure that we do not face this kind of a situation again,” Health Minister Rajitha Senarathana said in a telephone interview.

He added that in early August the government will introduce a new action plan prepared by WHO consultants and that he expected infections to slow down soon. Details of the plan are not yet publicly available.

The Sri Lanka Red Cross Society has had 300 volunteers working on dengue eradication. The organization also is beginning a six-month program involving many of its 6,000 volunteers in cleanup and in raising the population’s awareness of dengue risks, according to an action plan issued on Jul. 23.

(Reporting by Amantha Perera; editing by James Baer and Laurie Goering :; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, climate change, resilience, women's rights, trafficking and property rights. Visit news.trust.org/climate)