As the Arctic warms, mosquitoes—and the diseases they carry—float north. A recent study finds Jamestown Canyon virus and snowshoe hare virus present in mosquitoes in Arctic and sub-Arctic regions of North America. Here, a map shows locations in North America in which mosquitoes were sampled in a recent study from various collaborating research centers across Canada. Bubble size corresponds to the number of mosquitoes screened, categorized into four groups: small (<100), medium (100–300), large (301–1,000), and very large (>1,000). Numbers inside bubbles indicate species richness. (Figure originally published in Villeneuve et al 2025, Journal of Medical Entomology)

By Carolyn Bernhardt

Over the last couple of decades, a deluge of research and corresponding headlines have shown melting glaciers, rising sea temperatures, declining carnivore populations, and countless other effects of climate change on Arctic and Antarctic ecosystems. But recent research has revealed a new concern: shifting Arctic mosquito populations.

As climate change warms Arctic ecosystems, mosquitoes and other disease-carrying species are moving into new areas, where animals and people have never before been exposed to the germs that mosquitoes can carry. These changes pose serious health risks to both wildlife and humans, underscoring the need for a strategy that brings together experts in human, animal, and environmental health to monitor and prevent disease.

A recent study from various collaborating research centers across Canada shows humans and animals in the Arctic have now been subjected to the California serogroup (CSG) viruses, which include Jamestown Canyon virus (JCV) and snowshoe hare virus (SSHV). However, scientists still lack much information on which mosquito species are responsible for JCV and SSHV transmission in the Arctic. “I believe our findings should encourage public health agencies to prioritize research on vector competence in the Arctic,” says Carol-Anne Villeneuve, Ph.D., a postdoctoral researcher at Acadia University in Nova Scotia and lead author on the study, published in September in the Journal of Medical Entomology.

Monitoring mosquito populations can offer researchers an earlier warning of potential disease outbreaks than detecting infections in people or other animals. Still, environmental surveillance of insects in these remote areas has been limited until now, and current knowledge of Arctic mosquito vectors primarily comes from a few older regional studies. However, the effects of JCV and SSHV on human health are crystallizing. Both viruses can cause mild fevers to severe brain and nerve problems. The number of people with neurological diseases linked to mosquito-borne viruses has been increasing in North America, so JCV and SSHV are now considered emerging public health threats. This issue is critical in the Arctic, where people rely on local wildlife for food and are often exposed to mosquito bites.

To help address the knowledge gap on emerging risks of vector-borne diseases in the North American Arctic, the team of researchers set out with two primary goals: update information about which mosquito species live in the Arctic—especially those that might carry JCV or SSHV—and test Arctic mosquito populations to see if these viruses are present. The scientists conducted a mosquito surveillance program across northern Canada and the United States, working with local community members who helped collect mosquitoes using a simple, standardized butterfly net protocol. The program gathered data from eight sites during the summers of 2020, 2021, and 2022, covering four major Arctic and sub-Arctic biomes: the tundra, taiga, Hudson Plain, and Northwestern Forested Mountains.

As the Arctic warms, mosquitoes—and the diseases they carry—float north. A recent study finds Jamestown Canyon virus and snowshoe hare virus present in mosquitoes in Arctic and sub-Arctic regions of North America. Here, mosquitoes sampled in the study are collected in a small container. (Photo by Carol-Anne Villeneuve, Ph.D.)

Each biome has its own climate, vegetation, and landscape that influence mosquito abundance and diversity. The tundra, with its cold temperatures, open terrain, and short growing season, supports the fewest mosquito species. In contrast, the taiga and Hudson Plain offer warmer, wetter conditions and forested wetlands that provide ideal mosquito breeding grounds. The Northwestern Forested Mountains, with their mixed forests and varied elevations, may also host a range of mosquito species depending on local conditions. Because fewer insects can survive and reproduce at higher latitudes, mosquito diversity generally decreases toward the Arctic. Different animal communities in each biome also play a role in whether JCV and SSHV can persist and spread in these environments.

Over the course of the study, the team sampled more than 4,000 mosquitoes, identifying 18 species—17 of which were from the genus Aedes. They also reported new distribution records for Aedes euedes, Aedes implicatus, and Aedes spencerii. The team detected JCV in 10 mosquito species across seven sites, and SSHV in just one species at a single site.

The fact that researchers detected California serogroup viruses (CSGV) at every site—using only a butterfly net—shows that these viruses may be more widespread in the Arctic than once believed. It also shows that a simple, low-cost sampling method can still be highly effective.

Detecting viruses in less-studied mosquito species and in new northern locations expands scientific understanding of where these viruses exist. Notably, they recorded JCV in Ae. euedes, Aedes impiger, and Aedes pionips for the first time in North America. “What surprised me the most was that we found California serogroup viruses in the High Arctic, where only three mosquito species are typically found, and none of them were previously considered potential vectors for these viruses,” says Villeneuve. “This raises more questions about how the virus can persist in such harsh Arctic conditions and which mosquito species we should be most concerned about when it comes to vector surveillance.”

The broad distribution of JCV across species and locations suggests widespread enzootic transmission. This underscores the need to reassess the potential of Arctic mosquitoes as disease vectors in a rapidly changing climate and shows that Arctic mosquitoes may play a bigger role in spreading viruses than previously thought.

These impactful findings do come with some limitations, however. The distribution of mosquito species in the Arctic is dated, and the current understanding of their distribution may be inaccurate. In addition, sampling varied between sites and years—some locations had fewer or incomplete collection sessions. This made it harder to identify clear trends over time and may have affected which mosquito species were found. About 34% of mosquito samples were too damaged to identify to the species level. This limited the ability to study which species might carry specific viruses.

As the Arctic warms, mosquitoes—and the diseases they carry—float north. A recent study finds Jamestown Canyon virus and snowshoe hare virus present in mosquitoes in Arctic and sub-Arctic regions of North America. Here, a mosquito collected in the study is viewed under a microscope. (Photo by Carol-Anne Villeneuve, Ph.D.)

“The geographical coverage of this study is both a strength and a limitation,” says Villeneuve “Conducting research in the Arctic is challenging and expensive, but we were able to sample across a vast area, from the Yukon to Nunavik (Northern Québec). This level of coverage is rare in mosquito surveillance and provides a valuable snapshot of what’s happening across the Arctic as a whole.” However, she says, interpreting the data requires caution, as a single sampling site cannot possibly represent an entire territory. “It’s important not to generalize our findings or cause unnecessary alarm, especially when dealing with arboviruses that can affect human health.”

The team also collected mosquitoes during the daytime using butterfly nets, likely missing species that are more active at dusk or night. For example, Aedes provocans—a possible carrier of JCV known to live north of the 60th parallel—was not detected in any samples. RNA degradation during shipment may have reduced the ability to detect viruses, especially more fragile ones like SSHV. And lastly, one of the biomes had only a single sampling site, which made it difficult to compare results between different biomes.

Even with some limitations, this study provides new insights into mosquito distribution, diversity, and virus infections in northern Canada and Alaska. The research team says long-term and consistent monitoring will be key to tracking changes in mosquito behavior, diversity, and disease risk, especially as the climate continues to warm. Future studies should include genomic and phylogenetic analyses to better understand virus and mosquito relationships.

“Our research shows that the virus is present, and likely more widespread than previously thought, but without knowing which mosquito species are capable of transmitting it, there’s little that can be done to protect people beyond general precautions, such as wearing light-colored long-sleeve clothing and a mosquito head net when spending time outdoors during the summer,” Villeneuve says.

Now, she is working with the government of the Northwest Territories to standardize their mosquito surveillance program. “Our goal is to monitor mosquito populations at a finer, community-based scale, helping local communities learn more about the mosquito species in their area and assess potential health risks to both wildlife and humans,” she says. “We also want to improve how surveillance results are shared. These data are often not easily accessible to the public, and we want to change that by developing more transparent and open ways to communicate findings.”

Collaborating with Indigenous communities and sharing data with public health agencies will help improve efforts to track and manage mosquito-borne disease risks in the North, she adds. “I believe our findings should encourage public health agencies to prioritize research on vector competence in the Arctic,” says Villeneuve. “Once we have a clearer understanding of which mosquito species pose a risk, northern communities will be better equipped to carry out their own surveillance, focusing on identifying specific species rather than relying on costly virus testing, and will be less dependent on southern institutions, such as universities, for virus detection.”

Carolyn Bernhardt, M.A., is a freelance science writer and editor based in Portland, Oregon. Email: [email protected].