Warmer NC summers mean an increased risk of diseases and viruses. Here’s why.

The heat is on when it comes to the growing risk of contracting viruses and diseases thanks to climate change

Like the world as a whole, North Carolina is warming.

Thanks to human-induced climate change, especially from the pumping of increased amounts of heat-trapping greenhouse gasses into the atmosphere, temperatures are rising, starting earlier in the spring, pushing farther into fall, and producing more unpredictable weather events − especially storms and heavy rainfalls.

While that obviously means hotter days and nights, and all the associated heat-related health issues that come with that, it also means something a bit more invisible and sinister: An increased threat from viruses and diseases, whether incubating and spreading on their own or carried by vectors like mosquitoes that can thrive and expand their range in warmer climates.

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Hotter and hotter today and tomorrow

The World Meteorological Organization, the weather arm of the United Nations, said 2024 was the warmest year on record, approximately 1.55 degrees Celsius (2.8 degrees Fahrenheit) above the pre-industrial average. The result were deadly heat waves and wildfires across the planet and supercharged tropical weather systems, highlighted locally by Tropical Storm Helene that hammered Western N.C.

In North Carolina, data released by NOAA’s National Centers for Environmental Information showed 2024 to be the second warmest year on record, just behind 2019, with a statewide average temperature of 61.5 degrees.

According to the N.C. State Climate Office, five of North Carolina’s top six warmest years have happened since 2016, and each year in the past decade ranks among the top 22 warmest on record dating back to 1895.

According to the 2020 N.C. Climate Science Report, most parts of North Carolina are projected to see at least 2-3 additional weeks of very hot days (maximum temperature of 95°F or higher) for 2021-2040.

And the warming trend has continued into 2025. According to the climate office, July 2025 was the state’s second-warmest July on record. In Wilmington, the National Weather Service said July also was wetter and hotter than normal. According to the weather service, the average minimum temperature of 75.7 was a record for Wilmington. The normal average is 73 degrees. The Port City also tied a heat record.

“Wilmington’s temperature has dipped below 70 degrees F for the first time in 58 days,” the weather service posted on its Facbook page on Aug. 3. “This is tied for the second longest streak of 70+ low temps since records began here in 1874.”

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Mosquitoes and ticks

Hot weather isn’t just bad for creating a more heated environment. As water evaporates, it provides moisture for clouds and higher humidity levels, eventually increasing the chance of rain. While that can cool an environment over the short term, over the long term a warmer climate holds more water, leading to the increased risk of soaking precipitation events.

Meteorologists say climate change also is why tropical storms from Hurricane Katrina in 2005 to Tropical Storm Helene in 2024 to Tropical Storm Chantal this summer that swamped central North Carolina were more powerful and dangerous that they normally would have been.

Hot weather and standing water also are the perfect petri dishes for insects and other critters that are known to spread viruses, and climate change is allowing mosquitoes to have a longer season to breed, bite, and spread viruses.

An analysis by Climate Central found Wilmington had 11 more “mosquito days” − for a total of 221 − in 2022 compared to 1979. The nonprofit climate communications group defined “mosquito days” as having an average relative humidity of 42% or higher and daily minimum and maximum temperatures between 50 to 95 degrees. While the Port City’s numbers are trending in the wrong direction, it was better than what researchers found in Raleigh-Durham (+27 days), Greenville (+22 day) and Asheville (+22 days).

A warming climate also is allowing insects more time to hang around before the cold snap knocks them back. Species more commonly found in sub-tropical environments also are establishing footholds farther north as temperatures rise.

New Hanover County, for example, is home to more than 40 species of mosquitoes, several of which are non-native but have been able to adapt to the region’s climate. That increase in species, their range and potentially numbers is expected to continue as the weather gets warmer and more humid.

From a human health perspective, it’s the viruses the mosquitoes can carry more than the biting and general annoyance they can bring that worries public health officials. Those health risks include the Zika virus, dengue fever, Chikungunya virus, Eastern Equine Encephalitis and West Nile virus.

Ticks, another vector insect that is profiting from North Carolina’s warming climate, also is a stubborn and growing problem that can transmit the bacterial infections Rocky Mountain spotted fever and Lyme disease.

Historically, North Carolina has ranked near or at the top of the country for Rocky Mountain spotted fever, a disease caused by the Rickettsia rickettsii bacterium.

Emerging threats

Another bacteria that’s drawn a lot of attention this summer is Vibrio vulnificus, a flesh-eating bacterium that can cause serious illness and lead to sepsis, shock, and large blisters that destroy tissue. Humans can contract the bacteria from either eating raw seafood, especially oysters, or wading in brackish bodies of water while having an open wound.

The N.C. Department of Health and Human Services reported North Carolina had seen 59 cases of Vibrio infections through July 2025, including one death.

Cases of flesh-eating bacteria were once largely confined to the Gulf coast, but the U.S. Centers for Disease Control and Prevention said cases from 1988 to 2018 surged along the East Coast with an 800% increase. The bacteria’s range has been expanding as ocean waters warm up thanks to climate change, and the geographic range of infections has been marching north 30 miles per year.

Still officials preach pro-active measures, like staying out of the ocean if you have an open wound and treating any fresh cut immedaialy, should be enough to help keep the vast majority of beachgoers safe even while longer, warmer seasons allowing more bacteria to thrive.

The risk from a more common health hazard associated with fresh food also is expected to keep growing as climate change warms the planet.

Researchers at the University of Surrey in England found that weather factors, including warmer temperatures and higher humidity levels, can significantly increase the risk from salmonella, a type of bacteria that can cause food poisoning. It’s found in the intestines of animals and humans and can contaminate food if it’s not cooked or handled properly. Salmonella can cause diarrhoea, fever, and stomach cramps, and is most prominent in areas with poor sanitation and hygiene.

“The study highlights how weather plays a significant role in salmonella outbreaks and provides a valuable tool for predicting future risks and tailoring interventions, particularly in the context of climate change,” said Dr. Laura Gonzalez Villeta, the study’s lead author and a researcher at the University of Surrey, in a release.  

Reporter Gareth McGrath can be reached at GMcGrath@Gannett.com or @GarethMcGrathSN on X/Twitter. This story was produced with financial support from the Green South Foundation and the Prentice Foundation. The USA TODAY Network maintains full editorial control of the work.