Sri Lanka is currently facing a serious and widespread outbreak of dengue fever, raising urgent public health concerns across the island. Understanding why dengue spreads so rapidly requires more than simply knowing that mosquitoes carry the virus. According to Dr. Sarath Edirisinghe, a Consultant Medical Parasitologist, the specific behavioural patterns of mosquitoes — particularly those of the Aedes genus — play a decisive role in how quickly and how far dengue infection travels through communities. By examining these behaviours closely, health authorities and ordinary citizens alike can take more targeted and effective action to reduce transmission.
The Primary Mosquito Vectors Behind Dengue in Sri Lanka
Dengue is transmitted exclusively through the bites of mosquitoes belonging to the genus Aedes. In Sri Lanka, two species dominate as primary vectors. The first is Aedes aegypti, a mosquito that has adapted remarkably well to urban environments. It thrives in densely populated cities and towns where stagnant water is readily available in containers, flower pots, discarded tyres, and household water storage. The second species, Aedes albopictus, is more commonly found in semi-urban and rural habitats, often breeding in natural water collections such as tree holes, leaf axils, and bamboo stumps. Together, these two species create a transmission network that covers virtually every type of settlement across the country, making containment particularly challenging.
Feeding Habits That Accelerate Transmission
One of the most critical behavioural traits that makes Aedes mosquitoes such efficient dengue vectors is their feeding pattern. Unlike many other mosquito species that feed once before resting, Aedes aegypti is known to feed multiple times during a single gonotrophic cycle — the period between blood meals and egg-laying. This means a single infected mosquito can bite several people in quick succession, dramatically increasing the number of individuals exposed to the dengue virus during one feeding episode. This multi-host feeding behaviour is a key reason why dengue can spread so explosively within households and neighbourhoods in a very short period of time.
Daytime Activity: A Behaviour That Catches People Off Guard
Another distinctive and dangerous behavioural characteristic of Aedes mosquitoes is that they are primarily daytime biters. Most people associate mosquito bites with evening and nighttime hours and may take precautions accordingly, such as using bed nets or applying repellent before sleep. However, Aedes aegypti is most active during the early morning hours after sunrise and in the late afternoon before sunset. This daytime activity pattern means that standard protective measures used against night-biting mosquitoes are often insufficient. People are frequently bitten while going about their daily routines — working, studying, or simply relaxing indoors — without even realising they are at risk.
Breeding Preferences and Urban Expansion
The breeding habits of Aedes mosquitoes are closely tied to human activity, which is a major factor in the current dengue outbreak. Aedes aegypti has a strong preference for clean, stagnant water found in artificial containers. Rapid urbanisation in Sri Lanka has inadvertently created ideal breeding conditions, with construction sites accumulating water, poor waste management leaving containers exposed to rainfall, and urban households storing water in uncovered tanks. Even small amounts of water — as little as a bottle cap — can serve as a breeding site. This close association with human habitation means that eliminating breeding sites requires consistent community-wide effort rather than individual action alone.
Resting Behaviour and Indoor Transmission Risk
Aedes aegypti also displays a preference for resting indoors, particularly in dark, cool areas such as inside wardrobes, under furniture, and behind curtains. This indoor resting behaviour increases the likelihood of human contact and makes outdoor-only mosquito control measures largely ineffective. Indoor residual spraying and targeted indoor inspections are therefore essential components of any comprehensive dengue control strategy. Recognising that the threat exists within the home itself is a crucial shift in public awareness that health authorities are working to promote.
What Communities Can Do to Reduce Dengue Risk
Understanding mosquito behaviour translates directly into more effective prevention strategies. Communities should focus on eliminating standing water around and inside homes at least once a week, as the mosquito life cycle from egg to adult can be completed in as few as seven to ten days. Using personal repellents and wearing long-sleeved clothing during peak biting hours provides an additional layer of protection. Screens on windows and doors can help reduce indoor entry, while community clean-up campaigns targeting common breeding sites remain one of the most impactful collective actions available.
Conclusion
The behavioural patterns of Aedes mosquitoes — from their multi-host feeding and daytime activity to their preference for artificial breeding sites and indoor resting — collectively create the conditions for rapid dengue transmission. As Sri Lanka grapples with its current outbreak, the insights provided by experts like Dr. Sarath Edirisinghe serve as a vital reminder that effective dengue control must be grounded in a thorough understanding of mosquito biology and behaviour. Informed communities, supported by targeted public health interventions, remain the strongest defence against the continued spread of this potentially life-threatening disease.