For years, Iceland was known as one of the very few places in the world completely free of mosquitoes. However, that status officially came to an end in late 2025.
Three mosquitoes were discovered in an agricultural area in Kjos, a glacial valley in southwestern Iceland, marking the first recorded presence of the insects in the country. Following this discovery, Antarctica became the only region on Earth still free of mosquitoes.
How Did Mosquitoes Reach Iceland?
The discovery began through an accidental citizen science experiment. Bjorn Hjaltason, a local farmer, had set up a special string designed to attract moths when he instead noticed an unusual fly attached to it.
A few days later, two more specimens were found. The samples were then sent to the Natural Science Institute of Iceland, where entomologist Matthias Alfredsson confirmed their identity as Culiseta annulata, a mosquito species commonly found across Europe and North Africa.
How the mosquitoes reached Iceland remains uncertain. Alfredsson stated that the exact pathway is still unclear. However, experts suspect international trade routes played a major role.
Cargo ships, shipping containers, and international flights routinely transport goods to Icelandic ports. Mosquitoes hitchhiking inside temperature-controlled containers may have been able to cross the Atlantic without significant difficulty.
How Iceland Stayed Free of Mosquitoes for So Long
Iceland historically possessed a combination of natural conditions that made the environment highly hostile to mosquitoes. Extreme cold temperatures, unpredictable weather changes, and the lack of stagnant water made it difficult for mosquito life cycles to develop.
The country’s unpredictable freeze-thaw patterns during winter acted as a kind of ecological barrier: mosquito larvae that began developing during temporary warm periods would die once temperatures suddenly dropped again.
However, Culiseta annulata possesses a significant adaptive advantage. Unlike many mosquito species that rely on outdoor stagnant water, this species can survive winter by using human-made structures such as warehouses, barns, and basements as shelter.
By remaining inside these structures, the mosquitoes are protected from extreme outdoor temperature fluctuations and can re-emerge in spring fully active.
Arctic Warming and a Larger Ecological Shift
The arrival of mosquitoes in Iceland is not an isolated incident. The Arctic is warming four times faster than the rest of the planet, according to a study published in the journal Communications Earth & Environment.
In 2025, Iceland recorded its highest temperatures in history, including 26.6°C at Egilsstaðir Airport, far exceeding historical norms.
The impacts are already becoming visible across multiple sectors. Glaciers are collapsing, while warm-water fish species such as mackerel are increasingly being found in Icelandic waters.
In the United Kingdom, eggs of the Egyptian mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus) have also been detected. Both species are known vectors of tropical diseases such as dengue, chikungunya, and Zika.
In an editorial published in the journal Science, Amanda M. Koltz from the University of Texas at Austin and Lauren Culler from Dartmouth College argued that these developments reflect a broader ecological shift already underway as the Arctic continues to warm.
“Mosquitoes in Iceland are more than a curiosity or future annoyance. They are a warning,” the two researchers wrote.
What Risks Could Emerge in the Future?
For now, Culiseta annulata does not pose a major public health threat. Across mainland Europe, the species is generally regarded as little more than a biting nuisance rather than a carrier of dangerous tropical diseases.
The Natural Science Institute of Iceland is still investigating whether the three specimens represent an isolated incident or the beginning of an established breeding population.
What concerns scientists more is the absence of a coordinated arthropod monitoring system across the Arctic region. Koltz and Culler have called for the creation of a pan-Arctic monitoring network based on real-time data, emphasizing that Indigenous knowledge must serve as one of its foundations.
“The question is not whether the next surprise is coming, but whether it can be detected, interpreted, and acted upon before the window closes,” they wrote.
