Dengue Fever Sweeps Southeast Asia; Thailand, Laos, Singapore See Surge in Mosquito-Borne Illness; Unusually Early Rains Are Blamed

August 16, 2013, 7:13 p.m. ET

Dengue Fever Sweeps Southeast Asia

Thailand, Laos, Singapore See Surge in Mosquito-Borne Illness; Unusually Early Rains Are Blamed

NOPPARAT CHAICHALEARMMONGKOL

An early rainy season in Southeast Asia has led to an unexpected jump in cases of dengue fever as governments struggle to control the mosquito populations that transmit the disease. Video by WSJ’s Nopparat Chaichalearmmongkol.

BANGKOK—Southeast Asia is scrambling to combat a deadly outbreak of dengue fever, the tropical illness transmitted by mosquitoes, which has hit parts of the region especially hard. Health experts suspect that an unusually early rainy season that brought mosquitoes out in April, months ahead of what is expected, contributed to the seriousness of the dengue challenge. Also, above-average temperatures that many experts blame on global warming encouraged early mosquito breeding. Meanwhile, dengue is thought to be mutating as a result of immunity that has built up in the region. And as the virus is spread by travelers, more countries are expected to be affected.

The story in Southeast Asia is varied. Thailand, Laos and Singapore have seen sharp increases in infections compared with last year. Meanwhile, the Philippines, which has the largest number of deaths, at 306 so far, nevertheless has made some inroads as bringing numbers down from the 499 deaths in the year-earlier period, which health officials there attribute to education campaigns and antimosquito spraying.

The rise in death tolls in Thailand and neighboring Laos is of concern to health experts. Already 94 have died in Thailand, tripling the 32 who died there in the first seven months of last year. Meanwhile, in Laos, 76 have died, up from only three reported in the first six months of last year.

Meanwhile, financial center Singapore is facing its worst dengue outbreak ever. The city-state on Tuesday reported its fifth death this year but said weekly counts—which reached a record of 842 cases in the week ended June 22—have declined as the government intensified efforts to curb the outbreak.

So far the situation looks milder than last year in Vietnam and Cambodia, while Indonesia and Myanmar didn’t have data on dengue cases and deaths beyond March.

In other parts of Asia, Hong Kong, Japan and South Korea say they have seen increases in dengue, largely because of people returning from visits in Southeast Asia. China reports a jump in dengue, mostly because of a spike in the disease in July in Zhongshan, a city in southern Guangdong province.

India reported 3,952 cases in the year’s first quarter, more than double the 1,579 from the year-earlier quarter, although the number of deaths came down to seven from 12 in 2012. Infections in Taiwan and Australia are down slightly.

Aside from causing individual suffering, dengue also strains health services and results in economic losses. The Schneider Institutes for Health Policy at Brandeis University in the U.S. estimated in February that the annual economic burden of dengue in Southeast Asia is nearly $1 billion, with Indonesia and Thailand experiencing the highest costs.

In a bustling corridor of Bangkok’s Mission Hospital, physician Nick Walters this month recounted treating dozens of people walking in complaining of dengue symptoms. The arrivals began as early as April and May, months before the rainy season in July when dengue usually peaks.

“This year seems to be worse,” said Dr. Walters, an American missionary doctor and a tropical-medicine specialist who speaks fluent Thai and has been working with local and foreign patients in Bangkok for more than a decade.

The reported data back up Dr. Walters’s assessment, with Thailand’s infection numbers—at 99,358 infection cases as of Wednesday—triple what they were at this point last year.

Scientists haven’t developed an effective vaccine to prevent dengue fever. Treatment is limited to intravenous drips to try to replenish fluids victims lose as they struggle against fevers reaching as high as 105.8 Fahrenheit. Without timely treatment, victims can experience bleeding and shock.

Such symptoms could be seen in the dim rooms at the dengue ward of the Queen Sirikit National Institute of Child Health, a state-run hospital filled with young, weak patients, often with anxious parents at their bedside.

“I started to have fever and feel so shivered that I had to see the doctor,” said 13-year-old Pasinee Nualsri, who had faint red spots and rashes on her arms and legs and who had been in the hospital for nearly a week. “After a few days, the doctor said I might be infected with dengue.”

Prida Malasit, head of the Dengue Hemorrhagic Fever Research Unit at Thailand’s Mahidol University, said decades of observation suggest dengue outbreak tends to occur in three- to five-year cyclical peaks and troughs.

Southeast Asian countries report heightened efforts this year to control Aedes aegypti, the dengue-carrying mosquito that takes blood from an infected person and transmits it to the next person it bites.

Without a preventive vaccine or cure, these measures and rigorous public-awareness campaigns are the only tools to combat dengue.

In Bangkok, teams of municipal officers in jumpsuits armed with mosquito-killer spraying machines and masks fan out daily at houses and communities where dengue patients have been reported. Their task is to contain the probable spread of dengue by killing adult mosquitoes and wiping out their breeding sites.

“The increasing burden of dengue in the Asia-Pacific region is a matter of serious concern since the disease is spreading to new geographical areas,” said Dubravka Selenic Minet, a medical officer with the World Health Organization Thailand.

She said that among an estimated 2.5 billion people at risk globally, about 1.8 billion—more than 70%—reside in Asia-Pacific countries.