Singapore is on track to face its worst dengue outbreak in history

07/03/2020 Health, Technology, World


More than 14,000 cases of dengue have been reported in the city-state since the beginning of the year, according to the National Environment Agency (NEA). The total number for the full year is expected to exceed 22,170 cases reported in 2013, the largest dengue outbreak in Singapore’s history, the agency said.
Dengue is a viral infection transmitted by the Aedes mosquito, the same insect responsible for spreading zika, chikungunya, and yellow fever. It is commonly found in warm and humid regions of the tropics and subtropics during the rainy months.

Only about 25% of those infected show symptoms, including high fever, severe headaches, muscle and joint pain. Extreme cases can bring bleeding, respiratory difficulties, organ failure and potentially death.

In Singapore, 16 people died of dengue this year, double the number of deaths in 2013.

The warmest months from June to October are traditionally the high season for dengue in the city state, due to the accelerated development of the Aedes mosquito and the shorter incubation period of the dengue virus.

But this year, it has been particularly bad.

Last week alone, 1,468 cases were reported, the number of cases for the third consecutive week exceeded 1,000, and the highest number of weekly dengue cases ever recorded in Singapore.

In response to the skyrocketing cases, the Singapore government has stepped up controls to eliminate potential mosquito breeding habitats in public areas and housing estates.

Over the past three weekends, about 6,900 locations have undergone vector inspection and control, according to the NEA.

“Most of the detected mosquito breeding continues to be found in common areas of residential farms, premises and homes,” the NEA said in a statement Thursday.
And starting July 15, the agency will increase fines for people who don’t take steps to prevent mosquitoes from breeding both on and off their property. Mosquitoes are known to favor moist, dark corners and areas of standing water.

Why is it so bad this year?

Dengue cases have grown dramatically worldwide, increasing 30-fold in the past 50 years. There are an estimated 100 to 400 million infections each year, and about half the world’s population is at risk, according to the World Health Organization.
Scientists say the warmer, wetter climate caused by climate change has created the ideal conditions for female mosquitoes to lay their eggs. Not only are there more mosquitoes, but the rapid urbanization occurring in many Asian nations means that susceptible populations live in closer contact with disease-carrying insects.
How the climate crisis is accelerating the global spread of deadly dengue fever
Last year, the Philippines declared a national dengue epidemic in August. At the end of that month, 1,107 people had died of the disease and more than 270,000 had been infected.

In Singapore, experts believe a key reason for the rise in dengue cases this year is the return of an ancient strain of the dengue virus that has not been around for nearly three decades.

There are four strains, or serotypes, of the dengue virus. In Singapore, DENV-2 has been the dominant strain since 2016. But starting last year, the less common DENV-3 has been on the rise, according to Luo Dahai, associate professor of Infection and Immunity at Nanyang University of Technology.

“Considering that local outbreaks are generally caused by DENV1 and 2 in the past, the immunity developed among community residents against these DENVs may not be protective against emerging DENV-3,” said Luo.

According to the NEA, DENV-3 cases accounted for 48% of dengue cases in February, almost twice as many as DENV-2 cases.

“The increase in the proportion of DENV-3 cases is worrisome, as we have had no DENV-3-caused dengue outbreaks in Singapore for nearly three decades,” said NEA.

“This means that our population has less immunity to DENV-3, and consequently a large proportion of our population is susceptible to DENV-3 infection.” He said.

Have the closure measures worsened?

Another potential factor that aggravated the dengue outbreak this year, Luo said, could be the blocking measures imposed for the coronavirus.

In April, a second wave of infections erupted in Singapore among migrant workers living in crowded dormitories, sending new infections daily from fewer than 100 to more than 1,000 at their peak.

To contain its spread, the government issued an order to stay home and closed non-essential workplaces and schools. These restrictive measures, known as “circuit breakers,” lasted from April 7 to June 1.

“When more people stay home every day, there could be more residential mosquito breeding and more opportunities for ‘blood meals,'” Luo said.

According to the WHO, the female mosquito feeds during the day. The peak bite periods are early in the morning and in the afternoon before dusk.

NEA said it had observed a five-fold increase in mosquito larvae incidents detected in homes and common corridors in residential areas during the two-month circuit interruption period, compared to the previous two months. “The highest percentage of mosquito breeding found in households in the five main dengue areas was 84%,” he said.

CNN’s Helen Regan contributed to the reports.

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