Expanded Project Wolbachia helped prevent almost 4,000 dengue cases in 2023, study finds
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A close-up of male Wolbachia-Aedes mosquitoes photographed at the Wolbachia mosquito breeding facility on Feb 22, 2024.
ST PHOTO: GIN TAY
- Project Wolbachia's 2022 expansion prevented 3,798 dengue cases in 2023, about 28% of expected cases, according to a predictive model.
- The model uses climate data, dengue serotypes and El Nino/La Nina data, improving accuracy by 60% compared to seasonal data alone.
- NEA plans to cover half of Singapore's households (over 800,000) by October with Project Wolbachia to further prevent dengue spread.
AI generated
SINGAPORE – The expansion of Project Wolbachia in 2022 helped avert 3,798 cases of dengue – or about 28 per cent of expected cases – in 2023, according to a predictive model developed by international researchers and the National Environment Agency (NEA).
Using climate data and data on the four dengue serotypes, or strains, researchers estimated that 13,748 cases would have occurred in 2023 had the initiative not been expanded in the previous year.
Singapore reported 9,950 cases of dengue in 2023, with six deaths from the disease.
First launched in 2016, Project Wolbachia is an initiative to control the Aedes mosquito population here through the release of lab-grown male mosquitoes infected with the Wolbachia bacteria.
In 2022, NEA expanded Project Wolbachia from an initial five locations to an additional eight sites – including Hougang, Choa Chu Kang and Woodlands – covering more than 300,000 homes here.
By October 2026, more than 800,000 households here, or half of all households in Singapore, will be covered by Project Wolbachia as part of efforts to prevent the spread of dengue.
Research published in the New England Journal of Medicine in February found that the Aedes aegypti mosquito populations were reduced by 80 per cent to 90 per cent in areas covered by Project Wolbachia, with the dengue risk for residents in these areas falling by more than 70 per cent.
The new predictive model incorporates elements such as the monthly case percentages of the different dengue virus serotypes, data on the El Nino and La Nina phenomena, as well as the average monthly maximum temperature and total monthly rainfall.
Including data on the different dengue serotypes enhanced the predictive ability of the model beyond that of climate data alone, the researchers said. They found that incorporating climate information made the model 54 per cent more accurate than relying solely on seasonal case data, while incorporating information on the dominant dengue serotype improved its accuracy to 60 per cent.
Basing their study on over 20 years of data, the research team found that the risk of a dengue outbreak was highest during El Nino conditions and in the first few years following a change in the dominant dengue serotype.
The model is able to identify periods with higher dengue risk up to eight weeks in advance
The study was led by Dr Emilie Finch, a PhD student at the London School of Hygiene and Tropical Medicine at the time of the research, and Professor Rachel Lowe, a visiting professor at the NUS Saw Swee Hock School of Public Health.
The findings were published in the scientific journal Nature Communications in November 2025.
Associate Professor Ng Lee Ching, group director at NEA’s Environmental Health Institute, described the predictive model as a “valuable addition” to the agency’s range of tools for risk assessment.
Both the impact of climate and changes in circulating dengue serotypes were used as a proxy for changes in population immunity, said Dr Finch, now a postdoctoral researcher at the University of Cambridge’s pathogen dynamics unit.
“This allowed us to disentangle the effects of climate and serotype changes on dengue transmission in Singapore and improved our ability to predict dengue surges,” said the visiting researcher at the Barcelona Supercomputing Center’s (BSC) Global Health Resilience group.
“By combining climate information with disease surveillance, advanced modelling and high-performance computing, we can better understand how climate variability influences dengue dynamics,” said Prof Lowe, who also leads the Global Health Resilience group at BSC.
In 2025, there were 4,036 dengue cases here – a 70 per cent drop from the 13,651 recorded in 2024. According to NEA, 375 dengue cases were reported here in 2026 as at March 21, down 63 per cent from the 1,021 cases over the same period in 2025.
Mosquitoes in Singapore
While Singapore is home to over 180 mosquito species, only a handful transmit diseases. The most common mosquito genera – a category of biological classi cation – are Aedes, Culex and Anopheles. Although these mosquitoes are known to carry various diseases, only a few of these diseases are found here.
Aedes aegypti
While both male and female Aedes aegypti mosquitoes have black and white stripes on their bodies and legs and two white bands on their backs, males are smaller in size and possess feathery antennae.
PHOTO: NATIONAL ENVIRONMENT AGENCY
These mosquitoes are the main carriers of several viruses, including dengue, Zika and chikun
They can be identified by the black-and-white stripes on their bodies and legs, as well as two white bands on their backs in the shape of a lyre.
Male mosquitoes are smaller than females and have feathery antennae.
Females bite during the day and also in well-lit areas at night.
They breed in the still water left in ower pots, gutters and other water receptacles.
Aedes albopictus
Aedes albopictus mosquitoes have black and white stripes on their bodies and legs, similar to the Aedes aegypti, but are distinguished by a single white band on their backs.
PHOTO: NATIONAL ENVIRONMENT AGENCY
This species also has black-and-white stripes on its body and legs, but is distinguished by a single white band on its back.
These mosquitoes also spread dengue and chikungunya, albeit less ef ciently than Aedes aegypti.
Females bite during the day and also in well-lit areas at night.
In addition to still water in household areas, they breed in water found in green spaces, such as tree holes and leaf litter.
Culex quinquefasciatus
The Culex quinquefasciatus is a golden-brown mosquito with a dark proboscis, and is known as a carrier of Japanese encephalitis and Filariasis.
PHOTO: NATIONAL ENVIRONMENT AGENCY
These golden-brown mosquitoes possess dark proboscises.
They breed in blocked drains and bite at night.
The species is a carrier of Japanese encephalitis, which causes brain in ammation, and lariasis, which can cause severe swelling, fever and skin damage. These diseases are not endemic in Singapore.
Anopheles epiroticus & Anopheles sinensis
Anopheles epiroticus & Anopheles sinensis mosquitoes, which can carry malaria, are light brown in colour, with pale or dark scales on their legs and wings.
PHOTO: NATIONAL ENVIRONMENT AGENCY
These mosquitoes can be identified by their light brown colour, with pale or dark scales on their legs and wings.
They feed at night and breed in sunlit brackish pools with algae.
The species is a carrier for malaria, which is not endemic here.
