August through October is peak season for West Nile virus (WNV), and those of us living in South Carolina have a higher chance of exposure than most other places, according to Dr. Melissa Nolan, an epidemiologist at the University of South Carolina.
In a paper published in the American Journal of Tropical Medicine and Hygiene earlier this year, Nolan and her research team found that one in 10 South Carolinians is exposed to WNV -- 10 times the national average.
And the rate of WNV exposure is actually higher in Richland County and Columbia, where Nolan says one in five residents are exposed. The going theory, she says, is that the capital region has concentrated affluence.
“A lot of these more affluent areas are more likely to hire private companies to come out and spray for mosquitoes,” she says. “Those private companies are not required then to verify if there's insecticide resistance. So what we believe is happening is that you have these areas where people are spraying and creating insecticide resistance. So then you have these populations of mosquitoes that are actually thriving, and then in those areas, then you have heightened transmission.”
High transmission rates also have to do with the presence of birds, which migrate through the state in the spring and fall, thrive in lusher neighborhoods, and keep mosquitoes well fed.
According to the Centers for Disease Control (CDC), 80% of people bitten by an infected mosquito will experience no symptoms. Nineteen percent will experience flu-like symptoms that could last a few weeks. But about 1% can experience severe problems that affect the central nervous system and brain.
If there is good news, Nolan says, it’s that of the 62 varieties of mosquito identified in South Carolina, only one is a West Nile carrier — and she tends to be a night owl.
“This one likes to come out at dusk, and it will stay out all night long,” she says. “It actually peaks in activity at two in the morning. And she likes to go to sleep around dawn. So if you're out in the peak of the day, that is typically not the West Nile virus mosquito that's going to bite you."
Nolan says tipping out standing water, cleaning gutters, and using foggers can cut down mosquitoes on your property, at least temporarily. But she also reminds that your neighbors need to help to keep mosquitoes at bay.
“ It's not just your yard,” she says. “The West Nile virus mosquito can fly on average about a mile. So you definitely want to think about this as a community-based approach if you can.”
In August, the South Carolina Department of Environmental Services announced WNV outbreaks in the Midlands, Lowcountry, and Pee Dee. The CDC has reported 7 cases of West Nile virus in South Carolina this year.