Summer storms and floods create the perfect breeding ground for mosquitoes in the Carolinas

This summer, record-breaking flooding has left communities in central North Carolina reeling. But the danger isn’t over. Flooding can lead to a range of public health problems, even after the floodwaters recede.

Severe weather, and floods in particular, can facilitate the spread of disease. Sewer overflows and contaminated stormwater can spread gastrointestinal illnesses. And the standing water that floods leave behind, along with increased humidity, provides the perfect breeding ground for mosquitoes.

“Flooding can definitely create habitats where those mosquitoes can breed, whether that's in a natural pool of water or in containers that we may find around people's homes, like birdbaths, flower pots or tires,” said Emily Herring, who oversees the vector-borne disease program for the N.C. Department of Health and Human Services.

Eliminating those water sources can help reduce the spread of mosquitoes.

Humans are driving the rise in vector-borne diseases in several ways. Carbon pollution from vehicles, power stations and industry is raising global temperatures. Pest bugs like mosquitoes and ticks thrive in warm, humid climates, and much of the country, including parts of North Carolina, is experiencing a rise in the number of days these insects are active.

Human development can also facilitate the spread of vector-borne diseases like West Nile or dengue. These diseases aren't contagious — they spread only through the bite of their host organism.

A 2012 review of the relationship between infectious diseases and urbanization identified Dengue outbreaks, spread by the Aedes mosquito, as a "primarily urban problem."

"The Aedes mosquitoes live in and around houses. When a dengue epidemic occurs, it begins in cities and spreads centrifugally outward to neighboring city areas, suburbs and towns," the study said.

The U.S. saw a spike in dengue cases in 2024 — the disease appeared to be creeping up since 2020, but cases more than tripled in 2024, from 1,462 to 6,550.

When it comes to flooding and mosquitoes, timing is important. Last year, Helene flooded a region of western North Carolina where La Crosse encephalitis is more common. Fortunately, it did not result in a significant increase in La Crosse cases.

“The flooding impacted that region after the season, or the specific time of year when we tend to see La Crosse transmission,” Herring said.

Mosquito season has only just begun. In North Carolina, West Nile, eastern equine encephalitis and La Crosse encephalitis are the most common mosquito-borne illnesses. Most West Nile cases occur in August and September.