Tipping the Balance: A One Health Analysis of Climate-Driven Mosquito Expansion and Emerging Vulnerabilities (Case Study: Iceland)

Introduction:
Anthropogenic climate change is reshaping ecosystems and altering vector and pathogen distributions. The unprecedented discovery of Culiseta annulata in Iceland in 2025—previously one of the world’s only mosquito-free nations—signals a major ecological shift. This paper applies a One Health systemic review framework to explore the interconnections between climate warming, mosquito ecology, and emerging health vulnerabilities.

Methods:
This study systematically synthesized climatological, ecological, and epidemiological data from published literature, official databases (IPCC, ECDC, WHO, NASA Earth Observatory, Icelandic Meteorological Office), and verified news sources. Data were analyzed through a One Health lens to evaluate environmental, animal, and human health risks. A tripartite vulnerability assessment was conducted to identify potential cross-sectoral impacts.

Results:
Iceland’s 2025 record-breaking heatwave, with sustained temperatures above 20 °C for ten consecutive days, disrupted its historic freeze–thaw defense, allowing the successful breeding of C. annulata. The species’ cold-tolerant biology and overwintering strategy enabled permanent establishment. Findings indicate new ecological pressures, potential introduction of avian and livestock pathogens, and emerging human health risks in a previously naïve population.

Conclusions:
The colonization of mosquitoes in Iceland represents a climate-driven tipping point in sub-Arctic ecosystems. It demonstrates the tangible interdependence of environmental, animal, and human health within the One Health paradigm. Proactive integrated surveillance, research capacity building, and public awareness strategies are urgently needed to safeguard high-latitude regions against future vector-borne disease emergence.