Dengue virus 2 vector competence in heatwave-exposed Aedes aegypti mosquitoes is reduced by 5-methylcytosine RNA disruption.

Extreme weather events can profoundly alter the transmission dynamics of dengue virus (DENV) by its primary vector, Aedes aegypti. Understanding how mosquitoes respond to heat stress and how this affects viral transmission is critical for informing global public health strategies. RNA cytosine methylation is an evolutionarily conserved stress-response mechanism in A. aegypti that links environmental perturbations to shifts in RNA metabolism and gene expression. Here, we show that a 5-day heatwave initiated at the time of DENV2 acquisition increases the lifespan of surviving mosquitoes, thereby extending the window of potential virus transmission. Heatwave-exposed mosquitoes exhibit elevated global 5-methylcytosine RNA (5mC-RNA) levels and suppressed antiviral gene expression, facilitating efficient viral replication. Pharmacological disruption of 5mC-RNA with azacytidine counteracts heatwave-induced increases in transmission potential by enhancing antiviral transcription, reducing DENV2 infection prevalence from 78% to 37%, and restoring mosquito late-life survival to rates comparable to non-stressed controls. This integrative approach reveals an epitranscriptomic mechanism by which climate extreme scenarios like heatwaves can amplify dengue transmission risk, and highlights RNA methylation as a potential target for mitigating DENV transmission.