Dengue risk rises with bad air quality, high ambient temperature

Higher concentrations of particulate matter (PM) and carbon monoxide (CO), coupled with elevated ambient temperatures, appear to be driving an increase in the risk of dengue infections, according to a study from Singapore.

Analysis of 10-year data (2009–2019) showed that exposure to PM_2.5 levels ranging from 15.8 to 26.2 µg/m³ was associated with a 28-percent higher risk of dengue infections (relative risk [RR], 1.28, 95 percent confidence interval [CI], 1.11–1.49). The risk remained elevated across higher PM_2.5 levels, from 26.2 to 138 µg/m³. [Sci Rep 2025;15:13467]

Similar to PM_2.5, PM₁₀ showed a parabolic relationship with dengue risk. A 30-percent risk increase was observed at levels ranging from 27.5 to 40.4 µg/m³ (RR, 1.30, 95 percent CI, 1.12–1.51), with the association persisting at higher levels up to 155 µg/m³.

The risk of dengue infections also increased with CO exposure up to a threshold of about 1.2 mg/m³, with a 30-percent risk increase noted at levels ranging from 0.5 to 0.7 mg/m³ (RR, 1.30, 95 percent CI 1.06–1.61).

Ozone (O₃) at levels above 47.2 µg/m³ was negatively associated with dengue. Meanwhile, nitrogen dioxide (NO₂) had a complex, nonlinear association with the number of reported dengue infections. NO₂ concentrations between 24 and 41 µg/m³ were positively associated with the number of infections, with a 58-percent increase observed within the range of 23.3–33.3 µg/m³ (RR, 1.58, 95 percent CI, 1.25–2.00). At levels beyond 41 µg/m³, the association between NO₂ and the number of dengue infections was negative.

Temperature as a modifier

A rise in temperature of between 27.9 and 29.3 °C was associated with a 51-percent increase in the number of infections (RR, 1.51, 95 percent CI 1.23–1.85). Notably, temperature also modified the association between dengue and exposure to PM_2.5 and PM₁₀ (p<0.001 and p=0.01, respectively). The significant positive association observed between particulate matter and dengue at 27.9 °C was no longer evident at temperatures above 29.3 °C.

“This [effect modification] could potentially be due to higher mortality of mosquitoes at higher temperature, thus reducing the size of the infective population,” the investigators noted.

“Another explanation could be related to human behaviour. While an increase in PM concentrations would drive people indoors to seek refuge, higher temperatures may also modify mosquito–human interactions. For example, the increased use of air conditioning for heat relief may prevent mosquitoes from entering homes and reduce the probability of mosquito bites and thus the risk of infection,” they added.

Call to action

“Our study findings augment the body of evidence surrounding the impact of air quality variations on dengue transmission especially in Southeast Asia where the burden of dengue is among the highest across the world,” the investigators said.

They emphasized that interventions to lower dengue infection risk during predicted periods of elevated PM, carbon monoxide, and ambient temperature should be considered. For instance, health authorities could time the intensification of vector control efforts and public education campaigns ahead of anticipated spikes in PM to maximize dengue prevention, they added.

In addition, further studies are necessary to elucidate the potential effects of NO₂ or O₃ on mosquitoes, as well as the biological mechanisms through which these pollutants influence dengue transmission, according to the investigators.

The analysis involved a total of 107,128 reports of dengue between January 2009 and December 2019. The average number of dengue reports was 26.7, and the daily number did not exceed 50 daily cases for the majority of the days except for four notable periods in 2013, 2014, 2016, and 2019.

PM_2.5, PM₁₀, and CO exhibited concurrent concentration spikes over the same periods. O₃ did not appear to have any discernible seasonality, whereas SO₂ and NO₂ had inconsistent within-year concentration peaks. A high degree of collinearity was observed between PM_2.5 and PM₁₀, between PM_2.5 and CO, and between PM₁₀ and CO.