U.S. mosquito-control agencies are escalating surveillance and spraying as locally acquired dengue fever cases climb in Florida and other states, joining a broader summer surge of vector-borne illnesses that includes chikungunya travel warnings and Michigan’s first human EEE case since 2021.
Public health officials across the United States are racing to contain an expanding wave of mosquito-borne viral infections. While federal health authorities warn travelers about surging global infections, local mosquito-control districts face an active domestic spread of dengue fever in southern states and a rare, dangerous equine encephalitis case in the Midwest.
Dengue Surges Domestically as Florida and Virginia Report Local Transmission
Mosquito-control agencies are stepping up surveillance, property inspections, and aerial and ground treatments as locally acquired dengue fever cases rise in Tampa Bay and across Florida. As of Sept. 1, the number of dengue cases originating within Florida this year had climbed to 33 in Tampa Bay and 41 statewide, according to Fox News. The Florida Mosquito Control Association reported 30 confirmed cases in Hillsborough County, seven in Miami-Dade County, three in Pinellas County, and one in Palm Beach County.
Beyond Florida, public health data shows cases rising nationally. State health officials in Virginia and Florida each reported a locally contracted case in a single week according to The Independent. Federal health data tallies more than 1,455 local and travel-related cases across states including Texas, New York, California, Georgia, and Arizona.
“Dengue does not stop at county lines.”
Berro noted that while the mosquitoes transmitting the virus stay within a small area, daily regional travel allows infected individuals to introduce the pathogen to local mosquito populations. Hillsborough and Pinellas counties remain under mosquito-borne illness alerts issued by the Florida Department of Health. Nationally, federal data indicates that 2024 was a record year for dengue, with 3,798 reported cases across U.S. states and the District of Columbia—representing a 359 percent increase over the annual average recorded between 2010 and 2023.
Michigan Confirms Its First Human EEE Case Since 2021
While southern states battle dengue, Michigan health officials confirmed a human case of eastern equine encephalitis (EEE) in a Roscommon County resident, marking the state’s first human case of EEE since 2021. The Michigan Department of Health and Human Services reported that while no EEE detections have occurred in mosquitoes or animals so far this year, testing remains ongoing.
State and local health departments are trapping and testing mosquitoes in Roscommon County to assess local risk. As part of wider arbovirus surveillance, Michigan has also detected West Nile virus in mosquito pools across Detroit and multiple counties, alongside Jamestown Canyon virus in several jurisdictions.
Global Travel Advisories Expand as Climate Shifts Fuel Vector Habitats
The domestic cases coincide with heightened international concerns. The Centers for Disease Control and Prevention issued a Level 2 travel advisory for several nations and territories due to surging chikungunya cases, logging over 240,000 cases and at least 90 deaths worldwide since early 2025. Experts attribute the broader proliferation of these once-regional viral illnesses to warming climates, expanding mosquito habitats, urbanization, and international travel.
Health authorities across all affected regions continue to urge residents to eliminate standing water in containers like buckets, planters, and tires, wear protective clothing, and apply insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus to prevent bites.
