# It’s heating up - the rise of arboviruses *A changing climate brings threats of vectored diseases.* October 30, 2026 [ Jessica Oros ](/people/jessica-oros) As the summer wound down to a close, news headlines across the U.S. warned of continued mosquito-borne disease outbreaks. News outlets urged individuals to not forgo the bug spray on their outings, and virus names–West Nile virus, dengue virus–were thrown around. Taken together with the extremely active tick season, vector-borne diseases seem increasingly common in regions where they were once rare. At the root of this steadily spreading geographical range of viruses lies a phenomena commonly cited as the cause for negative environmental effects: the changing climate. But how is the gradually heating planet contributing to increased case numbers of viral diseases we have previously primarily associated with more tropical regions? To answer this question, we must look closely at the perpetrator of these diseases: arthropods. **Different species, different viruses** Arboviruses are spread to humans and other vertebrate animals by the bite of arthropod vectors, such as mosquitoes or ticks. There are over [3,700 species](https://www.cdc.gov/mosquitoes/about/index.html) of mosquito alone, each with slightly different genes that allow them to carry different viruses. For example, West Nile virus–known to cause flu-like symptoms or rare neurological disease–is primarily transmitted to humans through the bite of [*Culex* species mosquitoes](https://www.vdci.net/vector-borne-diseases/west-nile-virus-education-and-mosquito-management-to-protect-public-health/). In contrast, the [*Aedes* species](https://www.southernnevadahealthdistrict.org/faq-items/what-kinds-of-illnesses-does-the-aedes-mosquito-spread/) carries dengue virus, Zika virus, and Chikungunya virus, giving rise to body aches, birth defects, or debilitating joint pain, respectively. Additionally, ticks are known to carry pathogens including Colorado tick fever virus and the well-known bacteria-induced Lyme disease. The ability to carry different viruses comes down to the presence or absence of various factors that viruses require to survive in a vector. When mosquitoes bite an infected host, the virus replicates rapidly in the mosquito and then to the salivary glands, ready to be injected into a new host. Factors allowing viral entry, including cell-surface proteins called receptors or cellular immune factors may differ between mosquito species, in turn affecting which viruses can take root and multiply inside the mosquito. As such, the geographical range of a certain disease is largely connected to the habitat of its insect vector. ![Figure 1: Diagram of viral life cycle within the mosquito](/sites/g/files/omnuum5516/files/2026-10/Arbovirus%20Fig1_%20Mosquito.viral_.lifecycle.jpg) *Figure 1: Diagram of viral life cycle within the mosquito* **Spreading territory** Though mosquitoes and other disease-carrying arthropods are found all around the world, the climate of an environment often determines how well a mosquito population will thrive. This correlates with the geographical spread of the viruses they carry. As [global temperatures](https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature) increase, so too does the northernmost boundary of mosquito habitats. Climate predictions for the next several decades [anticipate *Aedes* mosquitoes](https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007213) creeping further into the northern U.S., with the possibility of bringing local transmission cycles of dengue or Zika virus in their wake. We have already begun to bear witness to the increasing range of such viruses. ![Figure 2: Distribution of Aedes and Anopheles mosquito species across North America over time](/sites/g/files/omnuum5516/files/2026-10/Arbovirus%20Fig2_%20Trial%20Mosquito%20Map.jpg) *Figure 2: Distribution of Aedes and Anopheles mosquito species across North America over time* Between 2009 and 2010, the first locally acquired case of dengue virus in the U.S. since 1945 was identified in Florida. Previously, dengue cases in the U.S. were primarily restricted to individuals who had travelled to regions where the virus is endemic. In recent years, however, the number of individuals arriving at the hospital with dengue who had not left the country has been increasing. Within the last 3 years, locally acquired dengue has been seen in [Virginia](https://www.vdh.virginia.gov/clinicians/clinician-letters/vdh-identifies-a-locally-acquired-case-of-dengue-virus-infection-in-northern-virginia-resident/), [California](https://www.cdc.gov/mmwr/volumes/73/wr/mm7342a4.htm), [Texas](https://www.cidrap.umn.edu/dengue/us-dengue-cases-jumped-359-2024-amid-global-surge), and Florida–where [one death](https://www.usnews.com/news/health-news/articles/2026-09-18/florida-confirms-a-death-from-dengue-as-the-state-struggles-with-one-of-its-worst-recent-outbreaks) last month signals one of Florida’s worst dengue surges in recent decades. In Massachusetts, another mosquito-borne virus, West Nile virus, has had a [reasonably average season](https://www.mass.gov/news/state-health-officials-announce-seasons-eighth-human-case-of-west-nile-virus-in-massachusetts)–but across the U.S., a warming climate may impact future West Nile virus case counts. While this virus only causes symptoms in about 20% of those infected, symptoms range in severity from flu-like effects to neuroinvasive disease. A [study](https://royalsocietypublishing.org/rspb/article/287/1932/20201065/85775/Thermal-thresholds-heighten-sensitivity-of-West) on the West Nile-carrying *Culex* mosquitoes of southern California found that, as temperatures increase, the percentage of virus-infected mosquitoes increases. As we see the increasing effects of a warming climate, such as the ongoing Super El Niño, this work [poses a possibility](https://vcresearch.berkeley.edu/news/how-worried-should-you-be-about-west-nile-virus) of greater mosquito-borne disease burden in the coming decades. **Collaboration and new directions** [Global institutions](https://www.paho.org/en/news/18-9-2026-paho-strengthening-nino-raises-growing-health-risks-across-americas) are calling for increased surveillance and vaccination against vector-borne pathogens in light of this season’s El Niño. While the possible strain on medical systems from increased arbovirus infection may be held at bay through proactive measures, the sanctity of these measures continues to be at risk. The environmental surveillance of mosquito populations seeks to identify circulating viruses before they infect people. Through trapping mosquitoes, labs can use a version of polymerase chain reaction (PCR) to search for the genetic information of these pathogens. Identifying viruses within a mosquito population can [inform public health](https://www.cdc.gov/west-nile-virus/php/surveillance-and-control-guidelines/index.html) measures such as targeted community education or mosquito elimination. Several labs at Harvard Medical School have been contributing to the goal of advancing viral surveillance and preparedness against vector-borne pathogens. In the [Abraham lab](https://abrahamlab.med.harvard.edu/), one of the research goals is to identify cell surface factors in humans, animals, and arthropods that allow entry of vector-borne viruses, contributing to the development of therapeutics against these pathogens. The [Perrimon lab](https://perrimon.med.harvard.edu/) uses CRISPR-Cas9 systems in mosquitos to investigate how they act as vectors for human disease as an extension of the Drosophila Research & Screening Center-Biomedical Technology Research Resource ([DRSC-BTRR](https://fgr.hms.harvard.edu/drsc-btrr)). The [Neafsey lab](https://hsph.harvard.edu/research/neafsey-lab/) at the Harvard T.H. Chan School of Public Health uses molecular and bioinformatics tools to gain a genomic perspective of mosquito-borne disease transmission. The work done by these labs and many others will give us insight into the changing sphere of vectored pathogens. In collaboration with large-scale viral surveillance and global health efforts, such as the World Health Organization’s (WHO) proposed [vector control response plan](https://www.who.int/publications/i/item/9789241512978), this research has the potential to fight the stark reality of a developing climate change-induced disease landscape. As the mosquitoes continue to adapt their habitat to the climate, we too must adapt our national and global approaches to combating disease. --- *This article was written by Jessica Oros (G4) with graphics designed by Peter Hoferle (G3).* See also:- [ Viruses in Focus ](/blog-topic/viruses-focus) Share on:- [ Facebook ](#) - [ Twitter ](#) - [ Linkedin ](#)