More than seven million Americans have been infected by the West Nile virus since it was first detected in the U.S. 25 years ago.
March 27, 2026 | Erin Bluvas, bluvase@sc.edu
With little historical data on the prevalence of the West Nile virus in the state of South Carolina, members of the Delores Marie Thomas Research Lab have assessed its presence in the Palmetto State. Led by epidemiology associate professor Melissa Nolan, the team published their findings in the American Journal of Tropical Medicine and Hygiene.
“The West Nile virus has undergone a number of evolutions since it was first detected
in the United States more than 25 years ago,” says Nolan, whose research focuses on
infectious diseases, particularly understudied vector-borne viruses. “We conducted
a vector-human-pathogen study of the virus’s current iteration to better understand
its habitat and transmission and found that the number of South Carolinians who had
been exposed to the virus was much greater than the national average. We also learned
that the mosquitoes that carry the virus were clustered in affluent urban neighborhoods
with greater tree canopy cover and abundant bodies of water.”
First discovered in the West Nile region of Uganda nearly a century ago, the West
Nile virus does not cause symptoms in the majority (more than 99%) of people. Unfortunately,
the remaining small percentage of infected individuals develop a neurological disease
characterized by infection and inflammation of the brain as well as paralysis. Those
who survive the acute phase of illness are likely to retain permanent disabilities,
such as autonomic dysfunction, chronic kidney failure, depression, retinopathy and
chronic fatigue syndrome.
The study, which took place during the summer of 2023, marked the sixth research project
– clinical, veterinary or epidemiology – to survey the presence of West Nile virus
since it was first discovered in South Carolina in 2003. The death of a Richland County
resident in 2022 due to the virus prompted USC scientists to lead a comprehensive
study in the same county.
22% of the SC participants sampled possessed West Nile virus antibodies compared to the national average of 2%.
Incorporating environmental, mosquito and human sampling, the multi-pronged study
focused on neighborhoods in downtown Columbia – per the recommendation of the state
public health entomologist based on previously recorded cases of infection. The research
team collected data using a free West Nile virus antibody test, an exposure and health
survey, and free mosquito sampling of the property surrounding participants’ homes.
“With 22% of the sampled residents possessing West Nile virus antibodies – a rate of more than ten times higher than the national average of 2% -- our research unearthed a hotspot for this infectious disease in central South Carolina,” says lead author Elba Fridriksson, an Arnold School alumna who is currently a clinical research coordinator at Prisma Health. “Our analysis also showed that 5% of the participants had antibodies that indicated a recent infection and that 3% of the mosquito pools we tested were positive for West Nile virus.”
“These findings are concerning not only because they reveal a much higher prevalence of West Nile virus than the national average but also because South Carolina’s estimated incidence rate was previously assumed to be less than 1%,” Nolan says. “Now that we have a better idea what we’re facing, prompt public health interventions, such more widespread clinical testing and mosquito mitigation efforts, are critically important to protect the health and well-being of South Carolinians. Additional research is also needed to better understand the roles of microenvironments, climate change and other risk factors that contribute to increased transmission of the West Nile virus.”
