Singapore’s dengue “emergency” is a climate change omen for the world

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Singapore's dengue "emergency" is a climate change omen for the world

The Southeast Asian city-state has already surpassed 11,000 cases – well above the 5,258 it reported in 2021 – and that was before June 1, when its traditional peak dengue season begins.

Experts warn that this is a grim number not just for Singapore – whose tropical climate is a natural breeding ground for the Aedes mosquitoes that transmit the virus – but for the rest of the world as well. That’s because changes in global climate mean that such outbreaks are likely to become more frequent and widespread in the years to come.

“[Cases] are definitely rising faster,” said Singapore’s Interior Minister Desmond Tan on the sidelines of a neighborhood inspection for dengue mosquitoes. “It is now an urgent emergency phase that we must deal with.”

The outbreak in Singapore has been exacerbated by recent extreme weather conditions, experts say, and its problem could be a harbinger of what is to come elsewhere as more countries experience prolonged periods of heat and thunderstorms that are helping to kill both the mosquitoes and the virus to spread you carry.

“The disease is now endemic in more than 100 countries,” the World Health Organization (WHO) said in a global dengue report in January 2022, noting that cases had increased “30-fold over the past 50 years.”

“Not only are cases increasing as the disease spreads to new areas, but explosive outbreaks are occurring.”

In 2019, the world saw a record 5.2 million cases of dengue, according to the WHO, and outbreaks across Asia killed thousands that year. Hundreds died in the Philippines and millions more were put at risk as the country declared a national dengue epidemic; in Bangladesh, hospitals were overwhelmed; and in Afghanistan, the transmission was recorded for the first time ever.
Singapore’s worst dengue outbreak in history happened the following year when it recorded 35,315 cases and 28 deaths.

So far this year, Singapore — where dengue has been endemic for decades — has seen just one dengue-related death, but with the rising number of cases, authorities are taking no chances.

“As of May 28, 2022, approximately 11,670 dengue cases have been reported this year – [with] about 10% of cases require hospitalization,” a spokesman for Singapore’s Ministry of Health told CNN.

Dengue admissions to hospital emergency rooms increased due to the recent spike, the spokesman said, but remained at “a manageable level.”

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But with the peak season just beginning, medical experts and doctors like Clarence Yeo Sze Kin say there is a chance this year to set a record for the number of cases.

“Dengue is a seasonal disease and once it gets hot and dry I usually see more patients coming in,” he said.

Yeo, who runs a clinic in downtown Singapore, is seeing a “sharp increase” in the number of patients with dengue-related conditions.

“Dengue may be endemic, but it’s by no means an easily treated disease,” Yeo added.

The ministry spokesman said most dengue cases did not require hospitalization or critical care. “However, some individuals can develop severe dengue fever, which can be fatal.”

“We remind the medical community of the appropriate clinical management of dengue cases and to maintain a high level of clinical suspicion when seeing patients with fever.”

Hotter days, warmer nights

Singapore’s dengue surge is the result of multiple factors including the recent warm, wet weather as well as a new dominant virus strain, said Ruklanthi de Alwis, a senior research fellow at Duke-NUS Medical School and an expert on emerging infectious diseases.

But climate change, she said, would likely make things worse. “Previous predictive modeling studies have shown that global warming due to climate change will eventually expand the geographic areas (where mosquitoes thrive) as well as the length of dengue transmission seasons,” de Alwis said.

The Singapore Meteorological Service says the Southeast Asian country is heating up twice as fast as the rest of the world. Maximum daily temperatures could reach 37 degrees Celsius by 2100 if carbon emissions continue to rise, weather scientists have warned.

Temperatures reached a record high of 36.7 degrees Celsius in May with oppressive humidity.

Soaring temperatures are expected to become the norm, according to weather and climate scientist Koh Tieh Yong of the Singapore University of Social Sciences.

“The past decade has been very warm. We are now experiencing about 12 more warm days and 12 more warm nights (compared to) 50 years ago.”

Koh said Southeast Asia has “a lot of concern about climate change” – although he said it is “currently not possible to scientifically establish the link between local heavy showers and climate change”.

Storm clouds in western part of Singapore.

Other experts said Singapore’s annual dengue problem is likely to only get worse given the trend of persistently hot weather and heavier rainfall from sudden torrential monsoons.

“We won’t be able to eradicate dengue (because) the constant weather extremes create perfect breeding conditions for mosquitoes,” said climate scientist Winston Chow of Singapore Management University’s College of Integrative Studies.

Chow, who has twice contracted dengue fever, lamented the escalating scale of the problem. “In terms of adaptation, Singapore has excellent health infrastructure and countless policies to reduce risks – but there is only a limited amount it can do,” he said.

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Despite tens of millions of dollars being spent every year to keep mosquito populations down through island-wide fogging efforts, public awareness campaigns and even novel experiments with special laboratory-bred mosquitoes, government agencies in Singapore continue to report increases in dengue infections and mosquito clusters.

“Singapore is currently facing a serious dengue situation,” the National Environment Agency told CNN, citing the “new warm, rainy and humid weather” as a big factor in the increase.

Dengue cases continue to rise sharply and are expected to remain high in the coming months, the agency added.

While the government agency has managed to eradicate large areas of congestion and has made extensive efforts to control mosquito populations, it still sees “excessive mosquito breeding” in many areas. “Rapid detection and removal of mosquito breeding habitat is critical to reducing the mosquito vector population,” the agency said. “We urge all residents to remain vigilant and thoroughly check their homes for standing water at least once a week.”

Here to stay

As climate change worsens and the planet warms, mosquito-borne diseases such as zika, chikungunya, and dengue are likely to continue to spread and have ever greater impacts on human health and well-being.

Experts say the important question now is whether politicians and policymakers – those who need to make the changes to slow climate change and prepare for its consequences – recognize the impact of mosquito-borne diseases on human health and take action.

“Changing environmental conditions are increasing mosquito breeding rates, making it even more difficult to completely eliminate the risk of dengue fever unless the climate emergency improves,” said climate scientist Chow.

“And it will be a painful struggle for Singapore in the long run.”

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