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Unmanaged plastic waste significantly increases dengue burden

This study introduces a material-specific extension of the WHO-recommended Breteau Index using Sri Lankan surveillance data to demonstrate that unmanaged plastic waste serves as a major breeding habitat, accounting for approximately 22–34% of the national dengue burden and providing a practical framework for linking waste management policies to infectious disease control.

Original authors: Prasad Liyanage, Sakunthala Janaki, Anoja Dheerasinghe, Preshila Samaraweera, Jagath Amarasekera, Sampath Weerakoon, Costas Velis, Marina Treskova, Joacim Rocklöv

Published 2026-07-27

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Prasad Liyanage, Sakunthala Janaki, Anoja Dheerasinghe, Preshila Samaraweera, Jagath Amarasekera, Sampath Weerakoon, Costas Velis, Marina Treskova, Joacim Rocklöv

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the world of tiny, invisible troublemakers: mosquitoes. Specifically, the Aedes mosquito, a fierce little fighter that carries dengue fever, a nasty virus that makes people feel like they've been hit by a truck. For decades, scientists have known that these mosquitoes love to lay their eggs in any little puddle of water they can find, especially in cities. They've also known that trash is a problem. But until now, the connection between a pile of garbage and a spike in sick people has been a bit fuzzy, like trying to solve a puzzle with half the pieces missing.

To understand this new research, you need to know about two main things. First, there's the "Breteau Index." Think of this as a scorecard that health officials use to count how many mosquito nests they find in a neighborhood. If the score is high, it means there are lots of baby mosquitoes hiding in water containers, and the risk of people getting sick is high. Second, there's the idea of "waste." We all know trash sits around, but we haven't always measured exactly how much of that trash turns into a mosquito nursery. This paper asks a simple but powerful question: If we start counting the trash specifically, does it help us understand why dengue fever is spreading? It turns out, the answer is a resounding "yes," and the trash in question is mostly plastic.

The Trash That Hatches Trouble

Scientists in Sri Lanka decided to play detective with a twist. Instead of just counting every mosquito nest they found, they started looking at what the nests were made of. They realized that the usual way of counting mosquitoes was like looking at a forest and just saying, "There are a lot of trees," without noticing that half of them are actually made of plastic bottles.

The researchers developed a new, super-specific scorecard called the Waste-Specific Breteau Index. Imagine you are a mosquito detective. Instead of just counting "water containers," you start sorting them: "Is this a flower pot? Is this a water bucket? Or is this an old yogurt cup, a soda bottle, or a discarded tire?" They found that the "trash" category—specifically non-biodegradable waste like plastic—was the biggest culprit. In fact, across the whole country, these discarded items were the most common place to find mosquito larvae, even more than traditional water storage or garden pots.

The Plastic Connection

But here is where it gets really interesting. The team didn't just stop at "trash." They wanted to know how much of that trash was actually plastic. Since they couldn't go back and re-sort every single piece of trash from the past two years, they ran a special pilot survey in eight districts. They went out, looked at the trash, and sorted it into "plastic" and "not plastic."

The results were eye-opening. They found that plastic made up more than half of the water-holding trash. Even more shocking, when they looked at the trash that actually had mosquito babies inside, plastic was the winner, accounting for nearly two-thirds of the positive spots. It turns out, plastic is a super-nursery for mosquitoes. It holds water, it doesn't rot away, and it creates the perfect shady, warm spot for mosquito eggs to grow.

The Numbers Behind the Nightmare

The team used some fancy math (called "hierarchical time-series models") to connect the dots between the amount of trash and the number of dengue cases. They found a clear, strong link: more trash meant more dengue.

Here is what the numbers tell us:

The Big Picture: In 2024 and 2025, the researchers estimated that about 30% to 34% of all dengue cases in Sri Lanka were directly caused by these trash-filled breeding grounds. That's roughly one out of every three cases!
The Plastic Share: When they zoomed in on just the plastic part, they estimated that about 22% to 23% of all dengue cases were specifically due to plastic waste.
The Human Cost: This isn't just about mosquitoes; it's about people. In 2024 alone, this trash-related dengue caused nearly 15,000 cases and cost the country about $4.8 million in healthcare and lost work time. In 2025, with a slight increase in cases, the cost jumped to $5.8 million.

Why This Changes Everything

For a long time, health officials have tried to stop dengue by telling people to empty their flower pots and cover their water tanks. While that helps, this paper suggests that we've been missing the biggest target: the trash on the streets and in the alleys.

The study argues that the old way of counting mosquitoes (the standard Breteau Index) wasn't bad, but it was too general. It was like trying to fix a leaky roof by just saying "there's water," without realizing the water is coming from a specific broken pipe. By creating a new index that specifically counts trash and plastic, health officials can now see exactly where the danger is hiding.

The paper suggests that if we want to stop dengue, we can't just spray insecticides or tell people to clean their yards. We need to fix the waste management system. If we stop plastic from piling up in the streets, we aren't just cleaning up the environment; we are literally cutting off the mosquito's supply chain.

The Bottom Line

This research doesn't claim to have solved dengue forever. It's a simulation and an estimate based on real data, not a magic cure. But it provides a powerful new tool. It shows us that the plastic pollution we see every day isn't just an eyesore; it's a direct driver of disease. By treating trash as a health hazard, not just an environmental one, we might finally get a handle on the dengue problem. As the authors put it, we need to connect the dots between the plastic we throw away and the mosquitoes that bite us, because in the battle against dengue, the trash can be the enemy.

Technical Summary: Unmanaged Plastic Waste Significantly Increases Dengue Burden

Problem Statement
Vector-borne arboviral diseases, particularly dengue, represent a rapidly expanding global health threat, with transmission dynamics increasingly driven by environmental and societal changes such as urbanization and climate variability. While the role of artificial water-holding containers in Aedes mosquito breeding is well-established, current surveillance frameworks lack the specificity to quantify how distinct waste materials contribute to disease risk. Conventional entomological indicators, such as the World Health Organization (WHO)-recommended Breteau Index (BI), measure overall larval habitat abundance but fail to distinguish between operational sources like discarded non-biodegradable waste and other container types. Consequently, the specific contribution of plastic pollution and unmanaged waste to dengue transmission remains poorly quantified, limiting the ability of public health and waste management sectors to implement targeted, integrated interventions.

Methodology
The study utilized a comprehensive, multi-stage analytical framework based on nationwide surveillance data from Sri Lanka covering the period 2024–2025.

Data Sources: The analysis integrated longitudinal data from 28 administrative health districts, including:
- Entomological Surveillance: Over 2 million inspections of potential larval habitats, classifying containers into 21 standardized types and aggregating them into five ecological categories.
- Disease Surveillance: Weekly district-level dengue case counts, mortality data, and clinical outcomes from the National Dengue Surveillance System (NADSys).
- Material-Partitioning Pilot: A targeted survey conducted in eight sentinel districts (March–June 2026) to classify discarded non-biodegradable waste by material composition (plastic vs. non-plastic) and quantify the proportion of plastic within positive breeding habitats.
Indicator Development: The authors developed two material-specific extensions of the Breteau Index:
- Waste-Specific Breteau Index ( $BI_{waste}$ ): Quantifies Aedes-positive discarded non-biodegradable waste containers per 100 inspected premises.
- Plastic-Specific Breteau Index ( $BI_{plastics}$ ): Derived empirically to estimate the plastic-specific component of waste-related breeding habitats.
Statistical Modeling:
- Exposure-Response Analysis: A two-stage hierarchical distributed lag non-linear model (DLNM) was employed to estimate the non-linear and lagged associations between entomological indices and dengue relative risk (RR) across 28 districts.
- Attributable Burden Estimation: Using the population attributable fraction (PAF) framework, the study estimated the number of dengue cases, deaths, and Disability-Adjusted Life Years (DALYs) attributable to waste and plastic habitats.
- Economic Evaluation: A cost-of-illness analysis was conducted from a societal perspective (2024 USD), incorporating direct health system costs, household out-of-pocket expenditures, and indirect productivity losses (morbidity and premature mortality) using a Human Capital Approach. Uncertainty was propagated via 5,000-iteration Monte Carlo simulations.

Key Results

Habitat Distribution and Infestation: Discarded non-biodegradable waste constituted the largest proportion of Aedes-positive habitats in the majority of districts (28.9% nationally) and exhibited the highest Container Index (17.6%), indicating a higher likelihood of harboring immature stages compared to ornamental, domestic, or water-storage containers.
Plastic Contribution: In the sentinel districts, plastic containers accounted for 65.8% of all positive discarded waste habitats and demonstrated a higher Container Index (15.5%) than non-plastic materials (11.5%).
Exposure-Response Relationships: The $BI_{waste}$ demonstrated the strongest, earliest, and most spatially consistent association with dengue relative risk. Significant risk emerged at the 36th percentile of exposure ($RR=2.53$), peaking at $RR=6.25$ at the upper exposure boundary. In contrast, the conventional BI showed a weaker, later threshold effect. The association was strongest in high-density urban settings and the Wet Zone.
Attributable Burden:
- National Level (2024–2025): Discarded non-biodegradable waste was estimated to account for 29.9% to 34.2% of reported dengue cases nationally, corresponding to approximately 14,789 to 17,654 attributable cases annually.
- Plastic-Specific Burden: In the pilot districts, plastic-associated habitats contributed approximately 22–23% of the dengue burden (5,748–5,870 cases annually).
- Health Outcomes: The waste-attributable burden resulted in an estimated 557–771 DALYs lost and 7–10 deaths annually at the national level.
Economic Impact: The societal cost attributable to waste-associated dengue was estimated at USD 4.83 million (2024) and USD 5.82 million (2025). Health system costs represented the largest component, followed by productivity losses. Plastic-associated habitats in pilot districts contributed an estimated USD 2.1–2.2 million annually in societal costs.

Significance and Claims
The paper claims that unmanaged plastic waste is a measurable and significant driver of dengue transmission, accounting for approximately one-third of the clinically apparent disease burden in Sri Lanka. The primary contribution of this work is the development of a scalable, material-specific surveillance framework ( $BI_{waste}$ and $BI_{plastics}$ ) that translates environmental waste accumulation into quantifiable infectious disease risk.

The authors argue that this framework addresses a critical gap in current vector control by:

Enhancing Predictive Utility: Providing a more precise exposure metric than the conventional Breteau Index, which has historically shown inconsistent correlations with dengue incidence.
Informing Integrated Policy: Creating a bridge between vector control, municipal waste management, and global plastic pollution governance. By quantifying the health consequences of specific waste materials, the framework offers an evidence base for upstream interventions (waste reduction and management) alongside downstream vector control.
Economic Justification: Demonstrating that environmentally mediated transmission generates substantial economic losses even during non-epidemic years, suggesting that investments in waste management could yield significant public health and economic returns.

The study concludes that refining habitat characterization allows routine surveillance to better capture the environmental processes linking mosquito breeding to disease transmission, supporting "One Health" strategies that integrate environmental protection with disease prevention.