Wolbachia mosquito releases to reach half of Singapore households by 2026 to combat dengue

SINGAPORE: Releases of Wolbachia-carrying mosquitoes will reach 50 per cent of all households in Singapore by 2026, Minister for Sustainability and the Environment Grace Fu said on Monday (Nov 25). 
The expanded release will reach 800,000 households in Singapore, providing coverage to areas at risk of large dengue outbreaks, Ms Fu said during the 8th Singapore International Dengue Workshop held at Jen Hotel Tanglin. 
Since the start of Project Wolbachia in 2016, Singapore has been progressively releasing Wolbachia mosquitoes across the country. 
Under the project, male Aedes aegypti mosquitoes that carry the Wolbachia bacteria are released to mate with the female Aedes mosquitoes. The eggs that are produced do not hatch.
Male mosquitoes do not bite and cannot transmit disease as they feed only on plant juices, such as nectar.
The authorities conducted a multi-site field study from July 2022 to determine the impact of the Wolbachia technology on dengue cases and clusters, as well as its effect on the Aedes population. 
Ms Fu announced on Monday the conclusion of the study.
Latest data from the completed multi-site field study indicated that residents of Wolbachia-Aedes release sites are about 75 per cent less likely to be infected with dengue due to an 80 to 90 per cent reduction in the Aedes aegypti mosquito population, she said.
These findings were consistent with results from NEA’s earlier trials. 
“We have also found that residents living in non-release sites adjacent to release sites were 45 per cent less likely to contract dengue compared to those living in sectors with no releases.
“This spillover effect suggests that neighbouring communities stand to benefit from releases as well,” she said. 
Ms Fu noted that the expected mid-year surges in dengue cases in 2023 and 2024 were “largely subdued” despite a high baseline of dengue cases, low population immunity and high mosquito numbers in some non-release areas. 
“Wolbachia coverage, together with strong and sustained community vigilance against breeding, has likely helped to avert large outbreaks,” she said. 
“After six decades of continued efforts to prevent and control dengue, a person living in Singapore today is ten times less likely to acquire a first-time dengue infection compared to the 1960s,” she said.
She noted however that a large proportion of the population was dengue-naive.
“This low population immunity, together with climatic conditions that are conducive for mosquito breeding and the continued presence of dengue viruses, leaves us still vulnerable to large outbreaks,” she added. 
As of Nov 16, Singapore has had 13,057 reported cases of dengue in 2024, compared to the total of 9,949 in 2023, and 32,173 in 2022.
“Insights from studies of mosquito behaviour now guide our deployment strategies, and the integration of automation into production and release operations has boosted our in-house capacity 40-fold compared to the manual process we started with,” the minister added.
“This decade-long investment in R&D (research and development) has been essential for NEA to learn how to deploy the technology effectively and efficiently, and forms a strong foundation for further scaling.”
In October, Singapore also announced the expansion of Project Wolbachia to five additional sites – Serangoon Central, Serangoon North, Jurong East, Jurong West, and an expansion of an existing study site in Hougang. 
Project Wolbachia currently covers more than 520,000 households, or about 35 per cent of households in Singapore. This will increase to 580,000 households in the first quarter of 2025. 
Ms Fu said the authorities will step up capacity at the two existing Wolbachia mosquito production facilities and establish a third facility.
So far, Wolbachia technology has been used in Singapore to “suppress and sustain low dengue mosquito populations to prevent dengue outbreaks”.
NEA will now go a step further to pilot it in areas with active, intense dengue transmission, the minister added. This will help it understand Wolbachia’s utility in interrupting the development of large and long-lived clusters.
“If effective, this new application of Wolbachia as a cluster management tool could complement traditional outbreak response operations,” Ms Fu said. 
In an accompanying media release, the NEA noted that it typically takes about three months of releases to achieve “significant reductions” in the mosquito population.
It added that the Wolbachia releases may not show immediate impact on dengue transmissions, but may have the potential to limit the growth of prolonged dengue clusters.