October 2024: Dr. Ross Boyce
Assistant Professor in the Division of Infectious Diseases at the University of North Carolina at Chapel Hill School of Medicine
La Crosse Virus: Appalachia’s Neglected Tropical Disease
“If this were happening anywhere but Appalachia, it would be identified as a neglected tropical disease. Ten cases of malaria in the U.S. makes national headlines, but we have hundreds of cases of La Crosse virus year after year. It is unacceptable that more resources have not been put toward a largely preventable disease affecting children in historically disadvantaged communities.”
Dr. Ross Boyce

North Carolina accounts for almost a quarter of all reported cases of neuroinvasive La Crosse virus (LACV) infections in the U.S., with 175 cases reported between 2011 and 2020. The Western part of the state bears the largest burden of disease with children accounting for most cases. In severe cases the virus affects the nervous system leading to brain inflammation—also known as encephalitis— altered mental status, and seizures. Potential long- term consequences of the disease include epilepsy, learning difficulties, and behavioral issues.
Dr. Boyce and his team at the Infectious Disease Epidemiology and Ecology Lab at UNC-Chapel Hill in partnership with Dr. Brian Byrd and Western Carolina University are examining the clinical outcomes and geographical risk factors of LACV in Western North Carolina, with the objectives of improving the effectiveness of care for LACV patients and reducing transmission in affected communities.
What is the La Crosse virus and how is it affecting children in North Carolina and the U.S.?
LACV is a mosquito borne virus that infects humans, but primarily causes symptoms in children. The disease is largely geographically restricted to the hardwood forests of the Appalachian Mountains ranging from South Carolina up through the Ohio River Valley. The number of reported cases fluctuates between 50-150 per year. On average, North Carolina alone accounts for nearly a quarter of all cases. Clinical symptoms range from mild fever, headache, and fatigue to more severe effects such as encephalitis (swelling of the brain). While the disease is rarely fatal, it can result in hospitalization and long-term side effects such as epilepsy and learning disabilities.
A lot of effort is going into identifying exactly “where” the virus is located. How does geographic location affect the prevalence of LACV? What are the implications of researching a virus that’s in your own backyard?
For an insect transmitted disease, there are three necessary conditions (i) the insect (in this case, a mosquito), (ii) the pathogen (disease causing agent) and (iii) people. In some cases, another mammal (called an amplifying host) is needed to keep the virus circulating in the environment.
In the case of LACV, the eastern tree hole mosquito (Aedes Triseraitus) carries the virus and has a preference for breeding in the tree holes of hardwood trees found mostly in rural, Western parts of the state. Its amplifying hosts are small forest mammals such as chipmunks and grey squirrels. There are related species of mosquitoes in Central North Carolina, but they have different breeding patterns, habitat preferences, and are probably not as effective in transmitting the virus to humans.
I grew up toward the Western part of the state and spent my childhood hiking and canoeing in the foothills. I feel rooted in that community. The disease is happening to my neighbors. I’ve learned some interesting lessons from Uganda; an observation is that I had better tools to address malaria there than for LACV here in North Carolina. This really speaks to the neglected nature of the disease.
Are there any current efforts to raise awareness of LACV?
In my experience, people who are impacted by the disease are shocked to learn it exists. Most people have never even heard of LACV. Raising awareness is important, but with relatively few cases, and those that do occur are found in historically disadvantaged areas of the country, there is still a lot of heavy lifting left to do. Dr. Brian Byrd, an entomologist and expert in vector-borne infectious diseases at Western Carolina University, has been on the forefront of LACV research for nearly 20 years and has been a driving force in understanding the virus. I am able to contribute a clinical perspective as we work to bring attention and investment toward better diagnostics, treatments, and ways to target the mosquitoes themselves.
What are the potential benefits of your research for future LACV patients and for managing the disease in this region?
We have begun developing sustainable protocols and procedures to systematically identify infected patients, eliminate disease vectors and build an ever-growing knowledge base for the virus.
For example, this year we were able to identify a hospital case of LACV and collect cerebrospinal fluid (CSF) from the patient. Soon after identifying the patient, Dr. Byrd collected mosquito specimens from their yard that also tested positive for the disease. We are currently in the process of testing the patient’s CSF to evaluate if the virus in the patient and the virus in the mosquito were genetically similar.
From a public health perspective, this shows the residual risk of disease transmission at a household. The good news is, we might be able to take steps to eliminate the disease-carrying mosquitoes at this home. With our protocol, we can identify families of infected mosquitos and, thereby, eliminate large transmission risks in these areas for a relatively small investment. My hope is that our work will continue to bring more attention and resources to LACV and improve public health efforts in affected regions.