Yes, and they do it here. In 2026 South Carolina declared West Nile virus outbreaks in three regions, and Virginia Beach recorded five cases. Still, the chance that any single bite makes you sick is low, and the people at real risk are fairly easy to identify. This guide covers which mosquito-borne diseases actually occur in South Carolina, North Carolina and Virginia, how likely you are to get sick, which symptoms mean you should see a doctor, the myths worth dropping, and what protects you and your pets.
Yes, mosquitoes spread disease. In the Carolinas and Virginia the main one is West Nile virus, which the CDC calls the leading cause of mosquito-borne disease in the contiguous United States. Eastern equine encephalitis (EEE) is much rarer but more dangerous. Mosquitoes also spread heartworm to dogs and cats.
Most infections are mild. The CDC says about 8 in 10 people infected with West Nile have no symptoms, and fewer than 1 in 100 develop the severe form. People 65 and older and people with weakened immune systems face the most risk. Mosquitoes cannot spread HIV.
Which Mosquito Diseases Occur in SC, NC and VA?
| Disease | How common here | How serious |
|---|---|---|
| West Nile virus | The most common by far. As of September 29, 2026, the CDC listed 22 cases in South Carolina, 22 in Virginia and 10 in North Carolina this year | Usually mild or no symptoms. Fewer than 1% of infections become severe, and about 1 in 10 severe cases is fatal (CDC) |
| Eastern equine encephalitis (EEE) | Rare. From 2003 to 2025 the CDC recorded 14 cases in North Carolina, 6 in South Carolina and 2 in Virginia | The most dangerous. About 30% of people who develop severe EEE die, and many survivors have lasting neurological problems (CDC) |
| La Crosse encephalitis | Rare. The CDC says most cases occur in upper Midwestern, mid-Atlantic and southeastern states | Severe illness occurs mostly in children under 16 |
| Dengue, Zika, chikungunya | The Asian tiger mosquito can carry them, according to the American Mosquito Control Association (AMCA). The CDC reports only limited local spread of dengue in the US. Most risk is in places like the Caribbean, Central and South America and Southeast Asia | Depends on the disease. Check CDC travel notices before trips |
| Heartworm (pets) | Spread by mosquitoes to dogs, cats and ferrets | Serious and potentially fatal in pets. Prevention is the only protection for cats |
West Nile in 2026
This was an active year. In August, South Carolina's Department of Public Health declared a West Nile outbreak in the Pee Dee after two cases there, then outbreaks in the Midlands (four cases) and the Lowcountry (two cases). An outbreak declaration means cases appeared close together in time and place, showing the virus was actively circulating there. In Virginia, the CDC's county data shows five cases in Virginia Beach, four of them the severe neurological form. In North Carolina it lists three cases in Mecklenburg County and one in Wake County.
South Carolina may see more exposure than most of the country. A University of South Carolina team led by epidemiologist Dr. Melissa Nolan published a study in 2026 estimating that about 1 in 10 South Carolinians has been exposed to West Nile, 10 times the national average. In Richland County and Columbia, she told South Carolina Public Radio, it's about 1 in 5.
How Likely Are You to Get Sick From a Mosquito Bite?
For any single bite, the chance is very small. Only some mosquitoes carry a virus, and most infected people never feel ill. The CDC's numbers for West Nile:
- About 80% of infected people have no symptoms.
- About 20% get a fever with headache, body aches, joint pain, vomiting, diarrhea or rash.
- Less than 1% develop severe illness affecting the brain or spinal cord, such as encephalitis or meningitis.
- About 10% of those severe cases are fatal.
Risk isn't spread evenly. The CDC says people 65 and older are three times as likely to develop the neurological form as younger people, and people with cancer, diabetes, high blood pressure, kidney disease or weakened immune systems are also at higher risk.
Severe cases can be life-changing. Under a Denver7 news story about a West Nile survivor, one commenter wrote: "I spent 3 months in icu. Nine months later I'm still having trouble walking." Under another news story, a commenter described lasting short-term memory loss and trouble sleeping. The CDC notes that even mild illness can leave fatigue and weakness for weeks or months.
West Nile Symptoms and When to See a Doctor
The CDC says symptoms usually start 2 to 6 days after the bite, though it can be anywhere from 2 to 14 days. Watch for:
- Fever with headache, body aches or joint pain
- Vomiting, diarrhea or a rash
- Fatigue that lingers
Get medical care right away for a severe headache, stiff neck, confusion, high fever, muscle weakness, numbness or seizures. These can be signs of the severe neurological form. There is no vaccine or medicine for West Nile in people, according to the CDC, but hospital care helps people with severe illness. Antibiotics don't work on viruses.
Recovery usually brings lasting protection. The CDC says most people who've had West Nile are believed to have lifelong immunity.
Which Mosquitoes Carry It, and When They Bite
Not every mosquito in your yard is a disease risk. Dr. Nolan told South Carolina Public Radio that of the 62 kinds of mosquitoes identified in South Carolina, only one carries West Nile, and it bites at night. "It actually peaks in activity at two in the morning," she said, so the mosquito biting you at midday is usually not the West Nile one. She also noted it flies about a mile on average, so control works best as a neighborhood effort.
That's useful for timing. If you're outside at dusk or after dark in late summer, that's when protection matters most. The Asian tiger mosquito, the striped daytime biter, is the one behind most backyard complaints.
Season matters too. Dr. Nolan puts West Nile's peak in South Carolina at August through October. The CDC's EEE data shows the same pattern: most cases begin in July, August and September.
Myths About Mosquitoes and Disease
- "Mosquitoes can spread HIV." They can't. The AMCA says HIV doesn't replicate in mosquitoes, and mosquitoes digest the virus. It estimates that about 10 million mosquitoes would have to feed on a person with HIV and then on someone else to produce a single infection. That also covers the common worry about a mosquito biting an HIV-positive person and then you right after.
- "You can catch West Nile from someone who has it." Not through everyday contact. The CDC says it doesn't spread by coughing, sneezing or touching. Rare cases have come through blood transfusions, organ transplants and from mother to baby.
- "Mosquitoes spread Lyme disease." They don't. Lyme disease is spread by ticks. This one comes up often: under a TV station's fact-check video on the subject, one of the most-liked comments claimed a friend got Lyme from a mosquito.
- "Dead birds are dangerous to touch." The CDC says you can't get West Nile by touching live animals, but you should still avoid bare-handed contact with any dead animal. Use gloves or double plastic bags to put a dead bird in the trash.
Can Mosquitoes Spread Disease to Pets?
Yes. Heartworm is the big one. The American Heartworm Society explains that a mosquito picks up microscopic young worms when it bites an infected dog, fox or coyote. Within 10 to 14 days they develop into the infective stage, and the mosquito passes them on with its next bite. The worms take about 6 months to mature and can live 5 to 7 years in a dog.
Many infected dogs show no signs early on. Later signs include a mild persistent cough, tiring easily, reluctance to exercise and weight loss. Cats can't be treated with the dog medication, so prevention is their only protection. The society's advice is to "think 12": test your pet every 12 months and give heartworm preventive 12 months a year.
How to Protect Yourself and Your Family
- Use an EPA-registered repellent with DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD or 2-undecanone, as the CDC recommends. Don't use oil of lemon eucalyptus or PMD on children under 3.
- Cover up at dusk and after dark in late summer and fall, when the West Nile mosquito is most active. Long sleeves and pants help, and permethrin-treated clothing adds protection.
- Dump standing water every week. The CDC says a mosquito goes from egg to adult in 7 to 10 days, so weekly is the minimum.
- Keep screens repaired and use air conditioning instead of open windows.
- Protect the most vulnerable. Older relatives and anyone with a weakened immune system should take the most care.
- Treat the yard where mosquitoes rest, such as shrubs, shaded walls and under decks. Dr. Nolan's team suspects that heavy residential spraying may be creating insecticide-resistant mosquitoes in some neighborhoods. That's one more reason to remove breeding water first and never spray more often than the label allows.
For the full yard plan, see how to get rid of mosquitoes in your yard and how often to spray for mosquitoes in the South. Our mosquito control service treats yards across South Carolina, North Carolina and Virginia, including mosquito control in Virginia Beach and mosquito control in Columbia.
Key Takeaways
- Yes, mosquitoes spread disease. West Nile is the main one in SC, NC and VA. EEE is rare but more dangerous.
- 2026 was active: outbreaks in three SC regions, 22 cases each in SC and VA and 10 in NC by late September.
- Most infections are mild. About 80% have no symptoms and fewer than 1% become severe. Age 65+ and weakened immunity raise the risk.
- The West Nile mosquito bites at night, peaking around 2 a.m., and the season peaks August through October.
- Mosquitoes can't spread HIV or Lyme disease, but they do spread heartworm to pets.
Frequently Asked Questions
Yes. In South Carolina, North Carolina and Virginia the main mosquito-borne disease is West Nile virus, which the CDC calls the leading cause of mosquito-borne disease in the contiguous United States. Eastern equine encephalitis is rarer but more serious, and mosquitoes also spread heartworm to pets.
West Nile virus is the most common. South Carolina's health department also lists eastern equine encephalitis and La Crosse encephalitis among the diseases mosquitoes can carry in the state. In 2026 the state declared West Nile outbreaks in the Pee Dee, Midlands and Lowcountry.
Very unlikely from any single bite. Only some mosquitoes carry a virus, and the CDC says about 80% of people infected with West Nile have no symptoms. Fewer than 1% develop severe illness, mostly people 65 and older or with weakened immune systems.
The CDC says symptoms usually start 2 to 6 days after the bite: fever with headache, body aches, joint pain, vomiting, diarrhea or a rash. A severe headache, stiff neck, confusion or muscle weakness needs medical care right away.
No. The American Mosquito Control Association says HIV doesn't replicate in mosquitoes, and mosquitoes digest the virus. It estimates about 10 million mosquitoes would have to feed on an infected person and then on someone else to cause a single infection.
No. Lyme disease is spread by ticks, not mosquitoes.
Not through everyday contact. The CDC says it doesn't spread by coughing, sneezing or touching. Very rare cases have spread through blood transfusions, organ transplants and from mother to baby.
At night. A University of South Carolina epidemiologist says the West Nile mosquito in South Carolina is active from dusk through the night and peaks around 2 a.m. The striped Asian tiger mosquito that bites during the day is usually not the West Nile carrier.
Yes. Mosquitoes pick up young heartworms from an infected animal and pass them on with their next bite. The American Heartworm Society recommends testing pets every 12 months and giving heartworm preventive 12 months a year.
Sources: CDC, "About West Nile", "Symptoms of West Nile", "West Nile: Causes and How It Spreads" and "Current Year Data (2026)", data as of September 29, 2026; CDC, "About Eastern Equine Encephalitis" and "Historic Data (2003–2025)"; CDC, "About La Crosse Encephalitis" and "Areas with Risk of Dengue"; CDC, "Preventing Mosquito Bites"; American Mosquito Control Association, FAQs; American Heartworm Society, "Heartworm Basics"; South Carolina Public Radio, "West Nile virus cases prompt outbreak declarations in the Midlands, Lowcountry" (Aug. 26, 2026) and "West Nile virus in South Carolina is much more common than the national norm" (Sept. 11, 2026).
Photo credits: James Gathany, CDC, Public domain; James Gathany, CDC, Public domain; Fir0002, CC BY-SA 3.0, via Wikimedia Commons.