As of September 2026, health officials report that dangerous mosquito-borne viruses are spreading across U.S. states. Florida and Virginia have recorded locally acquired dengue cases, while Michigan confirmed its first human case of Eastern equine encephalitis since 2021 in Roscommon County, prompting heightened mosquito surveillance and public health warnings.
Summer in the United States has brought more than just warm weather. Public health departments across multiple states are scrambling to contain mosquito-borne illnesses, navigating a landscape shaped by warming temperatures and an expanding insect habitat. While the vast majority of viral cases in the U.S. have historically been tied to travelers returning from international trips, recent weeks have seen a troubling uptick in locally acquired infections.
Dengue Surges in Florida and Reaches Virginia
The dengue virus is making a notable domestic push. Federal health data shows that cases have been climbing since the pandemic, propelled by warming temperatures linked to climate change. A study published in May revealed that U.S. dengue cases in 2024 outpaced the 2010 through 2023 annual average by 359 percent, with Florida accounting for more than a quarter of the nationwide total that year.
That momentum has carried forward. By September 1, locally acquired dengue cases in Florida climbed to 33 in Tampa Bay and 41 statewide, according to figures reported by Fox News. Hillsborough and Pinellas counties currently sit under mosquito-borne illness alerts issued by the Florida Department of Health.
“Dengue does not stop at county lines.”
Berro emphasized that while the disease-carrying mosquitoes stay within a confined radius, daily regional travel easily bridges the gap. When an infected traveler enters a new zone, local mosquitoes can bite them and pass the pathogen onward as cases rise across the region. Meanwhile, Virginia reported its first locally acquired case when an individual who had not traveled abroad came into close proximity with someone carrying a travel-associated infection as detailed by The Independent. State Health Commissioner Dr. Cameron Webb noted that despite the local detection, the overall acquisition risk for Virginia residents remains low.
Michigan Confirms Rare EEE Case in Roscommon County
While southern states battle dengue, the Midwest is confronting a far deadlier threat. The Michigan Department of Health and Human Services announced that a Roscommon County resident contracted eastern equine encephalitis, marking the first human case of EEE in Michigan since 2021.
EEE carries a 30 percent fatality rate among those who fall ill, and survivors often face permanent, disabling brain damage, personality disorders, seizures, or paralysis. Dr. Natasha Bagdasarian, Michigan’s chief medical executive, stressed the gravity of the detection in an official statement reported by the Detroit Free Press.
With no specific medical treatment available for EEE, intervention is strictly supportive. State officials are actively trapping and testing mosquitoes in Roscommon County while monitoring wildlife and domestic animals for further viral activity.
Targeted Response and Prevention Protocols
As state and local agencies ramp up aerial and ground treatments, mosquito-control crews are inspecting private properties to eliminate breeding grounds. Because the Aedes aegypti mosquitoes responsible for transmitting dengue are container breeders, they require small amounts of water to reproduce. Experts warn that discarded toys or plant saucers can serve as a viable nursery.
- Apply insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus.
- Dress in long sleeves, light colors, and closed-toed shoes when spending time outdoors.
- Dump standing water regularly from buckets, planters, tires, and outdoor containers around homes.
- Ensure window and door screens remain intact to keep insects out of living spaces.
Federal and state health surveillance will continue through the season as teams monitor mosquito pools for additional arboviruses, including West Nile virus and Jamestown Canyon virus.
