13 hours ago
Singapore's dengue numbers are down. Should we still be concerned about it?
There were 2,219 dengue cases between January and June 5, compared with the 10,000 cases in the first six months of 2024. PHOTO: ST FILE
Simply Science Singapore's dengue numbers are down. Should we still be concerned about it?
SINGAPORE – The number of dengue cases in Singapore has dropped significantly in 2025 , constituting only about a quarter of the cases recorded in the first half of 2024.
Data from the National Environment Agency's (NEA) website shows there were 2,219 cases between January and June 5, compared with the 10,000 cases in the first six months of 2024.
The agency attributed the decline in number partly to innovations such as Project Wolbachia – an initiative to control the Aedes aegypti mosquito population through the release of lab-grown male mosquitoes.
Does this mean that Singapore's control measures – which include fogging, home inspections and public education – are working, and that dengue is no longer a threat here?
Experts told Simply Science that it may be premature to say if the existing measures can curb future dengue outbreaks.
Under Project Wolbachia, male mosquitoes infected with Wolbachia – a common, naturally occurring bacteria – are released into high-risk dengue areas. When they mate with female mosquitoes, the eggs produced will not hatch, leading to a reduction in the mosquito population over time.
The initiative currently covers 23 areas in Singapore, including Bukit Batok, Tampines and Serangoon. It aims to protect 800,000 households, or about half of all households here, by 2026.
Studies have shown that residents in these areas are 75 per cent less likely to contract dengue, with the Aedes aegypti mosquito population in the areas falling by between 80 per cent and 90 per cent.
Professor Ooi Eng Eong of Duke-NUS Medical School described the addition of Project Wolbachia to Singapore's vector control programme since 2016 as a 'positive development', noting that the lower number in 2025 compared with the same period in 2024 is 'good news'.
'However, tempting as it may be, it is premature to attribute the current trends to any specific intervention,' said the expert in emerging infectious diseases.
Dengue epidemics do not occur annually but rather in five to eight-year cycles, said Prof Ooi, adding that fluctuations in mosquito population density are just one reason for the cyclical outbreaks.
'Other factors, such as population immunity to each of the four dengue viruses and genetic changes in dengue viruses circulating in Singapore, also affect dengue virus transmission and hence the number of dengue cases.'
There are four dengue serotypes, or strains, with DenV-2 having been the dominant one in the Republic since September 2023.
'Thus, although tempting, short-term changes in dengue case trends after the introduction of new dengue control measures should be interpreted with caution,' Prof Ooi said. 'Moreover, as our last epidemic was in 2022, trends in dengue cases in 2025 are likely too soon to conclude that the current control measures can effectively prevent future outbreaks.'
Professor Tikki Pang, a visiting professor at NUS' Yong Loo Lin School of Medicine, noted that similar initiatives in other countries, such as Malaysia, Indonesia and Australia, had shown positive results as well.
He cited two other possible reasons for the drop in dengue cases – seasonal variation and effective mosquito control.
Singapore typically sees fewer dengue cases outside the May to October peak period. NEA has also credited community vigilance – such as efforts to clear stagnant water to prevent mosquito breeding – as a key reason why a major outbreak was avoided.
In 2022, Singapore reported 32,325 cases of dengue, the second-highest annual total on record.
In May, NEA warned that despite the lower number of cases so far in 2025 , Singapore's low population immunity – as well as a global rise in cases – could potentially lead to an increase in dengue cases.
The agency noted that the May to October period usually sees higher dengue transmission here due to the accelerated development of Aedes mosquitoes and the more rapid spread of the dengue virus in the mosquitoes.
It reminded people to take actions such as overturning pails and changing water in vases to prevent the breeding of mosquitoes.
According to figures from the World Health Organisation, more than 13 million dengue cases were reported globally in 2024 – more than double the 6.5 million recorded in 2023.
Simply Science is a series that looks at the science behind everyday questions.
Zhaki Abdullah is a correspondent at The Straits Times. He is on the health beat, in addition to occasionally covering science, environmental, tech and Muslim affairs issues.
Join ST's WhatsApp Channel and get the latest news and must-reads.
