Jamestown Canyon Virus: An Emerging Arboviral Threat in Temperate Climates

By Pooja Toshniwal PahariaReviewed by Benedette Cuffari, M.Sc.

Introduction
Virology and transmission
Epidemiology and emergence
Clinical manifestations
Diagnosis and surveillance
Treatment and prevention
Climate change and range expansion
Conclusions and future outlook
References
Further reading

Jamestown Canyon virus is an emerging mosquito-borne threat in North America, with rising cases linked to climate-driven expansion of mosquito vectors. Diagnosis, surveillance, and prevention are challenged by cross-reactivity, lack of vaccines, and changes in ecology.

Image Credit: frank60 / Shutterstock.com

Introduction

Shifting climatic conditions and expanding mosquito habitats are increasingly enabling arboviruses to emerge in temperate climates. Among these viruses is Jamestown Canyon virus (JCV), which typically circulates throughout the United States and Canada. JCV is genetically stable, with closely related strains in Europe (Inkoo virus), and antibodies have also been found in wildlife in other temperate regions of North America.^2,4

Virology and transmission

JCV is a California serogroup virus in the genus Orthobunyavirus, family Peribunyaviridae. This virus is transmitted through the bite of infected mosquitoes, especially Aedes and Ochlerotatus species, as well as some Culex species.^2,4,10

White-tailed deer are the primary amplifying hosts in the United States. Antibodies and infections in other ungulates including mule, sika deer, moose, elk, caribou, bison, and pronghorn indicate broader ecological maintenance. JCV also infects livestock (e.g., horses and goats), though their role in transmission is unclear.²

JCV circulates between mosquitoes and viremic ungulate hosts. Mosquitoes acquire JCV while feeding, with subsequent bites potentially infecting humans or other mammals. Since human viremia is low, people are considered dead-end hosts. There is no evidence of direct person-to-person transmission, but very rarely, transmission could theoretically occur via blood transfusion or organ transplantation.²

Recent experimental studies show that Aedes aegypti is highly competent for JCV transmission, with viral loads rapidly reaching mosquito saliva after an infectious blood meal. Wolbachia-infected mosquitoes show only moderate blocking of JCV, in contrast to strong blocking of positive-sense viruses.¹⁰

Climate-driven range expansion of primary vectors increases the risk of JCV infection. To date, most reported cases are diagnosed between April and September, with peaks often observed in late spring and summer that reflect different mosquito populations.^2,3, 

Epidemiology and emergence

Since JCV was initially isolated from Culiseta inornata mosquitoes in 1961 in Jamestown, Colorado, sporadic human cases have been reported. However, JCV has become a widespread arboviral threat across the U.S. and parts of Canada, with higher infection rates reported in northern states such as Minnesota and Wisconsin. Genetic studies indicate a relatively high level of sequence conservation, even across strains isolated over 57 years and from geographically distant locations, suggesting evolutionary stasis.

Routine surveillance by the U.S. Centers for Disease Control and Prevention (CDC) has revealed a sharp rise in JCV cases, with annual reports increasing from about 2 per year before 2013 to nearly 30 per year after routine testing was introduced. Including multiple neuroinvasive infections, most reported cases occur in adults, and prolonged morbidity is common, though fatalities remain rare.^3,4

Improved diagnostics have undoubtedly contributed to rising case counts. Nevertheless, ecological factors like climate-driven mosquito range expansion and increased urban-wildlife contact also facilitate viral transmission. Seroprevalence studies in both humans and animals underscore the broad distribution of JCV across the U.S., Canada, and other regions of North America, thus highlighting its growing threat to public health.^{3,4, 5,6}

Clinical manifestations

Most JCV infections are asymptomatic or present as a mild, self-limited febrile illness. For symptomatic cases, the incubation period ranges from a few days to two weeks following a mosquito bite. Early symptoms include fever, headache, fatigue, and nausea, with some patients experiencing mild respiratory signs such as cough, sore throat, or nasal congestion. Respiratory involvement is more common in JCV than in other California serogroup viruses.^7,8

Severe disease, although uncommon, can manifest as meningitis or encephalitis, particularly in older or immunocompromised individuals. Neurologic symptoms such as stiff neck, confusion, altered mental status, seizures, and loss of coordination may be observed. Rare cases of neuroinvasive disease have also been reported in children.^2,4

Cerebrospinal fluid (CSF) pleocytosis occurs in severe neuroinvasive cases. Approximately half of the reported patients require hospitalization, though fatalities are rare. The Massachusetts case series showed no deaths but frequent prolonged neurologic symptoms.^4,7

Diagnosis should consider similar symptoms to La Crosse, Snowshoe hare, West Nile, Lyme disease, and other causes of meningitis and encephalitis. Unlike the La Crosse virus, which causes severe disease in children, JCV infections are more severe in adults.^5,7

Diagnosis and surveillance

JCV diagnosis can be achieved through the detection of JCV-specific or California serogroup immunoglobulin M (IgM) in serum and/or CSF by enzyme-linked immunosorbent assay (ELISA). California serogroup viruses cross-react serologically, which warrants confirmatory plaque reduction neutralization testing (PRNT) after positive IgM test results. Paired acute and convalescent sera with a four-fold rise in neutralizing titers indicate recent infection. Cross-reactivity is a significant challenge in diagnosis, and PRNT is essential to confirm JCV, especially in areas where other California serogroup viruses circulate.^8,9

Serology may be unreliable when tested early in illness or in severely immunocompromised patients. In these situations, molecular assays such as reverse-transcription-polymerase chain reaction (RT-PCR) on serum, CSF, or tissue can aid diagnosis. However, RT-PCR is often negative in serum, especially after the first few days of illness.  Molecular tools are not yet widely available but are currently being investigated to improve patient diagnosis and support mosquito pool surveillance where JCV co-circulates with other arboviruses.^4,8

JCV should be suspected in patients with acute febrile or neurologic illness and recent mosquito exposure in endemic regions. The neuroinvasive disease may cause CSF lymphocytic pleocytosis with elevated protein and normal glucose; therefore, ancillary studies such as lumbar puncture and magnetic resonance imaging (MRI) may be used to evaluate infection severity and exclude other causes.^7,8

Vector surveillance in Massachusetts has identified Ochlerotatus canadensis as a likely local vector, similar to findings in Connecticut. JCV disease is nationally notifiable in the U.S., with prompt reporting to local public health agencies supporting disease recognition and control. Despite these efforts, underdiagnosis and underreporting persist due to a lack of clinical awareness and limited facilities for specialized testing. Enhanced public health surveillance with expanded diagnostic capacity and molecular detection in mosquito vectors can improve situational awareness as ecological shifts alter vector distribution.^3,9

Treatment and prevention

There is no specific antiviral therapy for JCV disease. Management is supportive with an emphasis on rest, hydration, and over-the-counter (OTC) pain medications for mild cases. Severe neuroinvasive disease, such as meningitis or encephalitis, often necessitates hospitalization for intravenous fluids, pain control, antiemetics, and close monitoring for complications like elevated intracranial pressure, seizures, or respiratory compromise. Refractory seizures or cerebral edema may require intensive care.² No antiviral agents or vaccines are currently approved for prevention or treatment of JCV, although vaccine development is an area of ongoing research.^5,10

Due to the lack of a vaccine, prevention of JCV infection relies on minimizing mosquito exposure through personal protective measures. These include using Environmental Protection Agency (EPA)-approved repellents, wearing long sleeves and pants, treating clothing with 0.5% permethrin, and limiting outdoor activity during peak mosquito hours.^5,10

Community-level prevention focuses on vector control by eliminating standing water, larviciding, and habitat management, public education campaigns about mosquito-borne risks, and early detection systems to monitor mosquito populations and arboviral activity. Wolbachia-based mosquito control, which has shown efficacy against dengue and Zika, is less effective for JCV, with only moderate reduction in transmission observed in experimental studies. Strengthening these preventive strategies is crucial as the geographic range of mosquito vectors continues to expand.^5,10

Climate change and range expansion

Rising temperatures, milder winters, and altered precipitation, including heavier rainfall events interspersed with drought, are reshaping mosquito ecology in higher latitudes. Warmer conditions accelerate mosquito reproduction, shorten viral extrinsic incubation periods, and extend the duration that competent vectors can survive and bite.¹¹

Earlier spring thaws, longer frost-free periods, and increased availability of transitory water sources from rain, snowmelt pools, and human water storage during droughts can facilitate mosquito breeding. As these species spread further north and at higher elevations, the ecological envelope for JCV transmission expands in temperate zones.¹¹

Suburbanization, urbanization, exurban sprawl, and recreational land use bring people in closer contact with deer hosts and peri-domestic or woodland mosquitoes. Container habitats like gutters, planters, and tires, as well as fragmented green spaces near homes, can support vector populations during extended seasons, thereby increasing the risk of bites. In regions where white-tailed deer densities remain high at the urban-wildland interface, opportunities for JCV amplification and spread to humans may increase.^2,11

Conclusions and future outlook

Future research is needed to identify ecological factors contributing to JCV transmission, including the roles of deer reservoirs, dynamics of vector species, and climate-induced alterations in transmission patterns. To reduce transmission, integrated vector monitoring, habitat management, and mosquito population control will be required.^2,4,10

As climate change lengthens mosquito breeding seasons and expands vector habitats, public health planning must include climate-informed risk assessments, community education, and proactive prevention measures. By improving these interdisciplinary techniques, researchers will be better equipped to accurately predict and reduce the future impact of JCV on human health.^2,4,10

References

1. Coleman KJ, Chauhan L, Piquet AL, Tyler KL, Pastula DM. (2021). An Overview of Jamestown Canyon Virus Disease. Neurohospitalist. 11(3):277-278. DOI: 10.1177/19418744211005948, https://journals.sagepub.com/doi/10.1177/19418744211005948
2. Bennett RS, Nelson JT, Gresko AK, Murphy BR, Whitehead SS. (2011). The full genome sequence of three strains of Jamestown Canyon virus and their pathogenesis in mice or monkeys. Virol J., 8:136. DOI: 10.1186/1743-422X-8-136, https://virologyj.biomedcentral.com/articles/10.1186/1743-422X-8-136
3. Joseph D Poggi et al. (2023). Jamestown Canyon virus (Bunyavirales: Peribunyaviridae) vector ecology in a focus of human transmission in New Hampshire, USA, Journal of Medical Entomology, 60(4):778–788, DOI: 10.1093/jme/tjad046, https://academic.oup.com/jme/article-abstract/60/4/778/7128278
4. Kinsella, C. M. et al. (2020). Jamestown Canyon virus in Massachusetts: clinical case series and vector screening. Emerging Microbes & Infections, 9(1), 903–912. DOI: 10.1080/22221751.2020.1756697, https://www.tandfonline.com/doi/full/10.1080/22221751.2020.1756697
5. Muhammad Shahab et al. (2023). Immunoinformatics-based potential multi-peptide vaccine designing against Jamestown Canyon Virus (JCV) capable of eliciting cellular and humoral immune responses. International Journal of Biological Macromolecules. 253(2):126678. DOI: 10.1016/j.ijbiomac.2023.126678, https://www.sciencedirect.com/science/article/abs/pii/S0141813023035754
6. Data and Maps for Jamestown Canyon, Centers for Disease Control and Prevention (CDC), https://www.cdc.gov/jamestown-canyon/data-maps/index.html, Accessed on 23 July 2025
7. Kumar D et al. (2021). Jamestown Canyon virus-mediated meningoencephalitis with unusual laboratory findings. BMJ Case Reports;14:e242014, DOI: 10.1136/bcr-2021-242014, https://casereports.bmj.com/content/14/7/e242014
8. Rebekah A Sutter et al. (2025). Jamestown Canyon Virus Seroprevalence in Endemic Regions and Implications for Diagnostic Testing, Clinical Infectious Diseases, ciaf131, DOI: 10.1093/cid/ciaf131, https://academic.oup.com/cid/advance-article-abstract/doi/10.1093/cid/ciaf131/8096456
9. Pastula DM, Hoang Johnson DK, White JL, Dupuis AP 2nd, Fischer M, Staples JE. (2015). Jamestown Canyon Virus Disease in the United States-2000-2013. Am J Trop Med Hyg., 93(2):384-9. DOI: 10.4269/ajtmh.15-0196., https://www.ajtmh.org/view/journals/tpmd/93/2/article-p384.xml
10. Lau M-J et al. (2023) Jamestown Canyon virus is transmissible by Aedes aegypti and is only moderately blocked by Wolbachia co-infection. PLoS Negl Trop Dis 17(9): e0011616. DOI: 10.1371/journal.pntd.0011616, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0011616
11. John J. Shepard and Philip M. Armstrong. (2023). Jamestown Canyon virus comes into view: understanding the threat from an underrecognized arbovirus. Journal of Medical Entomology 60(6), 1242-1251. DOI: 10.1093/jme/tjad069, https://bioone.org/journals/journal-of-medical-entomology/volume-60/issue-6/tjad069/Jamestown-Canyon-virus-comes-into-view--understanding-the-threat/10.1093/jme/tjad069.short

Further Reading

• All Virus Content
• What is a Virus?
• What is the Difference Between Bacteria and Viruses?
• Virus History
• Virus Origins