Rare Mosquito-Borne Virus Confirmed in South Carolina: What You Need to Know About La Crosse Encephalitis

A rare mosquito-borne illness has been confirmed in South Carolina, raising awareness about the importance of mosquito bite prevention during the warmer months. Health officials have reported a confirmed case of La Crosse encephalitis in Oconee County, a viral infection that can lead to serious neurological complications in some individuals, especially children.

Although officials say there is no evidence of widespread transmission, the case serves as a reminder that mosquito-borne diseases remain a public health concern across parts of the United States. Here is what you need to know about the virus, its symptoms, how it spreads, and ways to protect yourself and your family.

Rare Case of La Crosse Encephalitis Confirmed in South Carolina

Oconee County Emergency Services announced on July 30 that a single case of La Crosse encephalitis has been confirmed in the county. Local officials are monitoring the situation alongside the South Carolina Department of Public Health.

Authorities emphasized that this is currently an isolated case. There is no indication that the virus is spreading widely within the county at this time. However, health experts continue to encourage residents to take preventive measures against mosquito bites.

The confirmation comes as mosquito activity remains high during the summer season, when warm temperatures and standing water create ideal breeding conditions.

What Is La Crosse Virus?

La Crosse virus is a mosquito-borne virus that belongs to the California serogroup of viruses. It is primarily transmitted through the bite of an infected eastern treehole mosquito, a species commonly found in wooded environments.

Unlike some infectious diseases, La Crosse virus cannot spread from one person to another. It is not transmitted through coughing, sneezing, touching, or casual contact. Infection only occurs through the bite of an infected mosquito.

The eastern treehole mosquito is unusual because it is most active during daylight hours rather than at dawn or dusk. These mosquitoes commonly breed in natural tree holes and artificial containers that collect rainwater, such as old tires, buckets, flower pots, toys, and other outdoor items.

Where Is La Crosse Virus Found?

According to the Centers for Disease Control and Prevention (CDC), La Crosse virus is most commonly reported in the upper Midwestern, Mid-Atlantic, and southeastern United States.

The mosquito responsible for transmitting the virus is found throughout much of the eastern and Midwestern regions of the country, making seasonal surveillance important in affected areas.

While infections remain relatively uncommon, cases are reported almost every year, particularly during late spring through early fall when mosquito populations increase.

Symptoms of La Crosse Encephalitis

Many people infected with La Crosse virus never develop symptoms. Those who do become ill usually begin experiencing symptoms between five and fifteen days after being bitten by an infected mosquito.

Mild symptoms may include:

• Fever
• Headache
• Nausea
• Vomiting
• Fatigue

In more severe cases, the virus can affect the brain and nervous system, leading to serious complications such as:

• High fever
• Neck stiffness
• Confusion
• Seizures
• Muscle weakness
• Vision problems
• Paralysis
• Brain inflammation (encephalitis)

Although rare, severe infections can be life threatening.

Children Face the Highest Risk

According to the CDC, severe La Crosse virus disease occurs most frequently in children younger than 16 years of age.

Children are more likely to develop encephalitis after infection, making early medical evaluation important if neurological symptoms appear after a recent mosquito bite.

Parents should seek immediate medical attention if a child develops persistent headache, high fever, seizures, confusion, or unusual drowsiness during mosquito season.

Current La Crosse Virus Cases in 2026

As of July 28, the CDC had reported four confirmed La Crosse virus cases in the United States for 2026. These cases were identified in:

• Alabama
• North Carolina
• Ohio
• Tennessee

The South Carolina case was announced after the CDC's latest national update, meaning it was not yet included in the federal case count.

Although the number of reported infections remains low, public health experts note that some infections may go undiagnosed because mild cases often resemble common viral illnesses.

Historical Cases in the United States

Between 2003 and 2025, the CDC recorded approximately 1,610 reported La Crosse virus cases nationwide, including 15 deaths.

Each year, roughly 30 to 90 severe cases involving the brain or nervous system are reported across the country.

Compared with more common mosquito-borne illnesses like West Nile virus, La Crosse virus remains relatively rare. However, its potential neurological complications make it an important disease for healthcare providers and public health agencies to monitor.

Mosquito Prevention Tips

Preventing mosquito bites remains the most effective way to reduce the risk of La Crosse virus infection.

Health officials recommend the following precautions:

• Use an EPA-registered insect repellent when spending time outdoors.
• Wear long-sleeved shirts and long pants in mosquito-prone areas.
• Repair damaged window and door screens to keep mosquitoes out of your home.
• Remove standing water from outdoor containers where mosquitoes can breed.
• Empty buckets, flower pots, bird baths, toys, tires, and other containers regularly.
• Be especially cautious near wooded areas where eastern treehole mosquitoes are commonly found.

Reducing mosquito breeding sites around homes can significantly decrease local mosquito populations.

Why Awareness Matters

Although La Crosse encephalitis is uncommon, awareness can lead to earlier recognition of symptoms and prompt medical care. Since there is no specific antiviral treatment for La Crosse virus, supportive medical care remains the primary approach for patients with severe illness.

Public health agencies continue monitoring mosquito populations and human infections throughout the summer to detect changes in disease activity.

Residents should not panic over a single confirmed case, but they should remain vigilant by practicing routine mosquito bite prevention, especially when spending time outdoors.

Final Thoughts

The confirmation of a rare La Crosse encephalitis case in Oconee County highlights the ongoing importance of mosquito-borne disease awareness. While officials have stressed that this appears to be an isolated incident, residents can lower their risk through simple preventive measures such as using insect repellent, eliminating standing water, and wearing protective clothing.

Most infections never become serious, but because severe illness can affect the brain, particularly in children, recognizing symptoms early and seeking medical attention when necessary remains essential.

Source: NTD Television report based on statements from Oconee County Emergency Services and information from the U.S. Centers for Disease Control and Prevention (CDC).

Disclaimer: This article is intended for informational and educational purposes only. It should not be considered medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional regarding medical concerns or symptoms. Statistics and public health information are subject to change as new updates become available.