Turning to nature to fight dengue
Using Wolbachia bacteria most effective method to tackle virus, says expert
PETALING JAYA: A nature-based method of controlling the spread of the dengue virus has shown to be the most effective strategy in curbing dengue fever, says an expert as the scourge surges worldwide and medical authorities bank on new vaccines and drug treatments.
World Mosquito Programme CEO Scott O'Neill said there is strong evidence in trials conducted in Indonesia showing the Wolbachia method has been the most cost-effective and sustainable way at tackling the virus by preventing its spread in the first place.
'High-quality clinical trials have shown that it can be highly effective, with a large trial in Indonesia showing a 77% reduction in cases and an 86% reduction in hospitalisations once deployed,' O'Neill told The Star in an interview.
According to the World Mosquito Programme's website, the method involves releasing mosquitoes infected with the Wolbachia bacteria into the local mosquito population.
The bacteria blocks viruses such as dengue, chikungunya and zika from growing in the bodies of Aedes aegypti mosquitoes, thus reducing the insects' ability to transmit these viruses to humans.
'When Wolbachia is established in a mosquito population it results in a decreasing incidence of dengue, zika and chikungunya,' the website said, adding that the bacteria is safe for humans and the environment.
Malaysia has also adopted this strategy by setting up 34 sites to release Wolbachia mosquitoes in Selangor, Johor, Penang, Kelantan, Melaka, Pahang, Kuala Lumpur and Putrajaya.
Last year marked one of the deadliest on record for dengue, with over 14 million cases and more than 10,000 dengue-related deaths worldwide, as reported by the European Centre for Disease Prevention and Control.
In Malaysia, the Health Ministry reported 122,423 dengue cases and 117 deaths in 2024, a slight decrease from 123,133 cases and 100 deaths in 2023.
Alarmingly, from Jan 1 to June 19 this year, there have been 29,717 cases recorded, with Selangor accounting for nearly half of these with 12,749, based on the ministry's iDengue site.
This is followed by Kuala Lumpur with 3,972, Johor (3,265), Sabah (2,081), Negri Sembilan (1,946), Kedah (1,218) and Perak (1,072).
At present, there are 280 active outbreak localities and 16 deaths have been recorded as of June 15.
O'Neill is doubtful that the rollout of new dengue vaccines could be the silver bullet against the disease.
'The first vaccine had worrying safety signals when administered on those who did not have dengue before, while the second has only been evaluated in two of the four dengue serotypes.
'Both of these vaccines require multiple carefully spaced shots to be effective. Given the efficacy of current vaccines and the challenges of administering them in a public health programme, they are unlikely to represent a solution for diseases like dengue by themselves.
'They will be a useful tool, though, to contribute to dengue control together with other approaches,' he said.
Last year, Malaysia's Drug Control Authority approved the first dengue vaccine for use in the country named Qdenga.
The vaccine is said to protect against all four dengue virus serotypes.
It is particularly effective against the serotype-2 virus (DENV-2), which is currently the dominant viral strain in Malaysia.
O'Neill also does not see repurposing drugs to treat dengue as a promising strategy.
'While a lot of work has been done on the possible use of antiviral drugs to treat dengue, the problem is that most patients seek care too late after the disease has progressed for the drugs to be effective,' he said.
Health Minister Datuk Seri Dr Dzulkefly Ahmad recently revealed that repurposing drugs to treat dengue is one of Malaysia's latest approaches to fight the disease.
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Tan Dengue fever, a mosquito-borne viral disease caused by the dengue virus (DENV), has remained one of the most pressing public health threats, particularly in tropical urban centers like Kota Kinabalu areas in Sabah. Transmitted primarily by the Aedes aegypti mosquito, dengue infections continue to escalate despite years of government-led interventions such as fogging, larviciding, and public health education. While these strategies have played a role in limiting outbreaks, a persistent and frequently overlooked factor continues to undermine control efforts: the household environment. The Institution of Engineers Malaysia (IEM) has formulated guidelines on the prevention and control of dengue for households to form a critical frontline in the war against dengue. Understanding and addressing the factors that allow mosquitoes to breed within and around homes is key to breaking the cycle of transmission. The Aedes aegypti mosquito has evolved to thrive in human-made environments. 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This includes commonly overlooked spots such as flowerpot trays, bathroom floor traps, kitchen sinks, laundry buckets, pet water dishes, and items left outdoors that may collect rainwater. However, inspections must go beyond simply tipping water out. Ae. aegypti eggs adhere to container walls and remain viable for months. Therefore, all water-holding items should be scrubbed, dried, and, where possible, stored in a dry position or covered to prevent refilling by rain or household use. A crucial but often under-managed aspect of residential design is water storage and rainwater harvesting. Many households, especially in semi-urban or water-insecure areas, rely on large containers to store water for cleaning or garden use. If these containers are left uncovered or only partially sealed, they become perfect breeding grounds. The IEM guidelines advise that all water storage should be fully sealed or covered with mosquito-proof mesh with apertures not exceeding 1.2 mm. Additionally, rainwater harvesting systems should be designed with self-draining features, overflow outlets, and flush systems to prevent water stagnation in gutters, downpipes, and filtration components. Where sealing is not practical, safe biological larvicides such as Bacillus thuringiensis israelensis (Bti) may be applied periodically. Roof gutter systems represent another hidden danger. Improperly installed or poorly maintained gutters trap organic matter such as leaves and silt, leading to blocked drains and water accumulation after rainfall. Slopes that are too shallow or absent of overflow mechanisms exacerbate this issue. According to the IEM, gutters should be cleaned at least monthly, and ideally be fitted with leaf guards, inspection ports, and anti-mosquito mesh over drain outlets. Any system collecting roof water should be designed with adequate fall gradient to ensure efficient flow and prevent pooling. The same attention must be paid to sanitation and household plumbing systems. Bathroom floor traps, unused toilets, and rarely used sinks can become stagnant if the water seal is not regularly replenished. Leaky pipes under kitchen cabinets or external taps can also result in puddles that serve as mosquito nurseries. It is advised that homeowners perform plumbing checks quarterly and fix leaking connections promptly. Floor traps and gully traps not in use should be sealed or treated with cooking oil, which forms a surface layer that suffocates larvae. Another often neglected contributor is poor waste management. Discarded items such as broken toys, cans, unused flowerpots, or even polystyrene containers left in gardens or porches can trap rainwater. In high-rise buildings, recycling materials such as plastic bottles or food containers stored in open-air spaces pose additional risk. The guidelines recommend that recyclables be punctured and dried before storage and always kept under cover. Homes should also undertake regular decluttering, particularly in outdoor areas and balconies. Community recycling centers and municipal contractors should support proper collection and disposal to reduce container waste exposure. While engineering solutions and technical recommendations form the backbone of prevention, behavioral change is what ensures their sustainability. Dengue prevention should become part of the household's weekly routine, alongside tasks such as sweeping or taking out the trash. Children should be taught to report stagnant water or mosquito sightings, while household helpers or tenants must be equally informed. Awareness campaigns rooted in WHO's COMBI (Communication for Behavioural Impact) model stress the importance of not just knowledge but habit formation. Posters, fridge magnets, and weekly SMS alerts have been successfully deployed in various localities to serve as reminders. When a suspected dengue case arises in a household, immediate containment is essential. The infected person should always sleep under a mosquito net, including daytime, to avoid being bitten by Aedes mosquitoes, which could then spread the virus. Simultaneously, the household should undergo a detailed inspection, not only of the patient's room but the entire compound. Neighbors must be alerted, and the local vector control unit — such as the Kota Kinabalu City Hall (DBKK) should be notified to conduct fogging or larviciding in the vicinity. In this effort, stakeholder collaboration is indispensable. Homeowners, property managers, developers and municipal authorities must work together to address shared spaces and structural risks. Developers have a responsibility to incorporate mosquito-resistant design in new housing schemes. This includes proper landscaping to avoid water retention, the use of permeable pavements, well-graded drainage systems, and the installation of sealed water tanks and inspection-accessible gutters. For high-rise or gated communities, property managers must schedule quarterly inspections of rooftop water tanks, basements and sump pits. Maintenance logs should be maintained and subject to health inspections. Local authorities play a crucial role in enforcement and education. DBKK (Kota Kinabalu City Hall) and related councils must uphold existing health by-laws that prohibit the harboring of mosquito breeding sites. This can include issuing compound fines or warnings to households found in violation during routine checks. Equally important is the provision of public education materials in multiple languages to reach all segments of the population, including migrant workers and the elderly. Sabah's unique climatic and demographic conditions further intensify the need for household-level dengue resilience. The state's equatorial rainfall patterns and hot temperatures create year-round breeding conditions, while many residents live in low-density housing with access to outdoor space — increasing exposure to container habitats. During the monsoon season, when rain is frequent and intense, mosquito populations can surge rapidly, outpacing fogging efforts. Therefore, household preparation and maintenance must be intensified before, during, and after seasonal peaks. Historical data from Kota Kinabalu district show that dengue outbreaks have occurred in predictable cycles, often corresponding to periods of sustained rainfall and stagnation of preventive efforts. The National Crisis Preparedness and Response Centre (CPRC) has noted that case clusters frequently originate from residential areas where multiple breeding sites are found within proximity. In one notable case in Kota Kinabalu district in 2022, over 60% of the breeding sites were traced to household premises, despite weekly fogging efforts in public spaces. This highlights the irreplaceable role of domestic source control. In conclusion, household-level dengue control is not merely an auxiliary component of vector management — it is the foundation upon which all other strategies rest. Engineering controls, environmental design, behavioral adaptation and policy enforcement must converge at the household level to sustainably reduce dengue transmission. The IEM Guidelines offer a scientifically grounded and practically implementable framework for empowering households to play a leading role in mosquito control. In a rapidly urbanizing city like Kota Kinabalu where human activity constantly reshapes the environment, household vigilance, maintenance discipline, and structural design must evolve in parallel. A mosquito-free home is not just a private benefit — it is public responsibility and a civic duty. As dengue continues to pose a threat to public health, the pathway to control lies not in complex technology, but in consistent, collective household action — one container, one drain, and one home at a time.
