JONATHAN M. METSCH, Dr.P.H. – Tracking Emerging Public Health Challenges – October 24, 2026 – DENGUE
“The Florida Department of Health is reporting an even greater number of cases. As of October 17, the state had tallied 425 locally acquired dengue cases in 11 counties. The greatest number — 346 — have been in Hillsborough County, which encompasses Tampa. Pinellas County, which includes St. Petersburg, has reported 51 cases.
By comparison, Florida had reported 650 locally acquired cases from 2010 to 2025, according to historic CDC data.
Hillsborough, Pinellas, and Pasco counties have repeatedly extended dengue-related states of emergency to shift funds into aerial spraying to kill mosquito larvae.
Until this year, cases had also been rising in Texas, California, Arizona, and Hawaii, but none of those states have reported any locally acquired illness in 2026. Virginia, however, reported its first locally acquired case earlier in the year, said Adams.”
“Six US territories and freely associated states also have frequent or continuous dengue transmission: Puerto Rico, American Samoa, the US Virgin Islands, the Federated States of Micronesia, the Republic of the Marshall Islands, and the Republic of Palau.
Older adults and those with comorbidities such as asthma, diabetes, obesity, and hypertension are at higher risk for dengue. Pregnancy has been associated with a higher risk for progression to severe disease, Adams said, adding that a second dengue infection also increases severity risk, but not a third or fourth infection.” (1)
“The CDC has issued a Level 3 emergency response for dengue outbreaks in Florida and another U.S. territory, the agency’s eighth emergency response activation this year.
Florida is in the midst of its largest dengue outbreak in decades, with 745 cases this year; 425 of those have been locally acquired, and most are concentrated in the Tampa area. That figure marks the largest dengue outbreak in the continental U.S. since 1935.
“Given the widespread presence of Aedes aegypti mosquitoes and with recent hurricane-related rainfall, continued domestic transmission remains a concern,” Chris Braden, MD, acting director of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), wrote in an email that was shared with MedPage Today.
Braden acknowledged the extraordinary number of responses managed by NCEZID staff this year. “I know many of you are already supporting active responses across the agency, and I am deeply grateful for your continued agility and dedication,” he wrote.
Other emergency responses included Cyclospora, Ebola, measles, hantavirus, and New World screwworm outbreaks, along with the World Cup safety activation and the Potomac River wastewater spill activation near Washington, D.C.
The other U.S. territory covered in Braden’s email is the Republic of the Marshall Islands, which has declared a state of emergency on its two largest islands, Ebeye and Majuro. Braden said the CDC “has been providing programmatic support and deployed an Epi-Aid team.”” (2)
“Ira Longini, a biostatistician and infectious-disease modeler at the University of Florida, said he’s not surprised by dengue’s continued spread.
“It was just a matter of time,” Longini said.
Longini explained that climate change is increasing mosquito populations and lengthening their active seasons, contributing to dengue’s spread globally.
He emphasized the importance of public campaigns to eliminate mosquito breeding sites. Mosquitoes breed in small pools of water, including in tires and plastic containers.
Cooler, drier weather could offer some relief, Longini said, by slowing or stopping transmission. However, any reprieve could be temporary. “If it warms up and there’s more rain, then it’ll come back,” he said.” (3)
“When the rains arrive and water collects in pots, tyres and terraces, so do the mosquitoes. For many families in monsoon-hit cities like Chennai, the first sign of trouble is a fever that comes with body aches and a headache, and the first question is whether it’s dengue, chikungunya or something else.
That is a fair question, because all three are spread by the same mosquito and can look almost identical in the first few days. We spoke to doctors about the clues that help tell them apart, why only a blood test can settle it, what to do at home, and the warning signs that mean heading to the hospital the same day.
Why they are so hard to tell apart
During seasons when mosquito-borne infections are prevalent, dengue, chikungunya and Zika can be difficult to distinguish because they often begin with similar symptoms, including fever, headache, muscle pain and body aches. However, according to Dr. Tushar Tayal, Associate Director, Internal Medicine, CK Birla Hospital, Gurugram, certain clinical features can help doctors identify the likely infection.
Early days can be tricky. “Difference between Chikungunya and Zika in the first two days is hard to tell. Both Chikungunya and Zika come from the Aedes mosquito, the same one that spreads Dengue,” says Dr. Sushila Kataria, Vice Chairperson, Internal Medicine, Medanta Gurugram. “Dengue, chikungunya and Zika can look alike in the first few days, but Dengue is the one I worry about most, because platelets can drop quickly,” she adds.
Dengue: severe body aches and falling platelets…,,
Chikungunya: the joints give it away…,,.
Zika: usually mild, but not for everyone….
Only a blood test can tell you which one it is. The key is not to rely on symptoms alone. “A patient’s travel history, local outbreak patterns, day of illness and clinical examination all guide the diagnostic approach,” Dr. Tayal explains, adding that laboratory tests, including appropriate molecular or antibody tests depending on the stage of infection, help confirm the diagnosis.” (4)
“(PAHO) called on countries in the Americas to strengthen surveillance and prepare health services in response to recent increases in dengue observed in several countries and increased and renewed chikungunya transmission in countries and territories where viral circulation had not been documented for several years.
The call comes amid the anticipated intensification of the El Niño phenomenon and as South America approaches the peak transmission season for these diseases.
In an epidemiological update published on October 20, PAHO reported that as of mid-September, 1.69 million suspected dengue cases had been reported in the Region, including 3,413 severe cases and 571 deaths.
Although the cumulative number of reported cases represents a 58% decrease compared with the same period in 2025, this decline has not been uniform across the Region: increases have been observed in recent weeks in countries in the Andean, Central American, and Caribbean subregions. Circulation of all four dengue virus serotypes has also been identified in the Americas in 2026.
PAHO also highlighted the chikungunya situation, with transmission increasing between late 2025 and 2026 and reemerging in countries and territories that had not documented viral circulation for several years. As of mid-September, 213,919 suspected cases had been reported, of which 78,481 were confirmed, along with 88 deaths in 20 countries in the Region.
The update also points to transmission in new areas, outbreaks outside historical transmission seasons, longer transmission periods, and increased reporting of more severe clinical manifestations.
Strengthening prevention and preparing health services
In response, PAHO urged countries to strengthen epidemiological, virological, and entomological surveillance, increase diagnostic capacity, and ensure early detection and timely clinical management of cases. The Organization also recommended stepping up integrated measures to control Aedes mosquitoes, the main vectors of these diseases.”
PAHO recommends that health services prepare to respond to potential increases in cases at all levels of care, with particular emphasis on strengthening primary health care capacity to recognize dengue warning signs early and prevent progression to severe disease. Hospitals should also be prepared to manage cases with dengue warning signs and severe cases of these diseases.
Eliminating mosquito breeding sites remains a key measure to reduce mosquito populations. PAHO recommends strengthening environmental management, eliminating containers that collect water, and promoting the active participation of communities, families, local authorities, and other sectors in prevention and control efforts.” (5)
A Tampa woman was diagnosed with dengue fever. Within a week, she was dead., If confirmed by public health officials, it would be Tampa Bay’s first dengue fever death in a century., https://www.tampabay.com/news/health/2026/09/08/dengue-fever-death-tampa-general/
Inside the fight against mosquitoes spreading dengue fever in Florida, https://www.tampabay.com/culture/2026/09/04/inside-fight-against-mosquitoes-spreading-dengue-fever-florida
Bangladesh dengue outbreak accelerates as hospitals come under strain, https://www.reuters.com/business/healthcare-pharmaceuticals/bangladesh-dengue-outbreak-accelerates-hospitals-come-under-strain-2026-09-07/
Parasite-infected mosquitoes released in Europe for first time, https://www.newscientist.com/article/2594886-parasite-infected-mosquitoes-released-in-europe-for-first-time/?fbclid=IwZnRzaAVHStlleHRuA2FlbQIxMQBwZG9mBWZkaWQWUQwdCWcm0KQ-3SEyQaTccnJSdt0je3NydGMGYXBwX2lkDzE3Mzg0NzY0MjY3MDM3MAABHlTo5a7MXrNdG5A1BQDrrO1omt14F6tawWnGuOu_4l6rFHBuMgqCbScjh4Zz_aem_eQBq8bsYqc1mvI3MWPcmxg&utm_id=97758_v0_s00_e0_tv1_a1demo0ecg7rma
1.Dengue Cases in 100 Years, by Alicia Ault, https://www.medscape.com/viewarticle/florida-tallies-highest-locally-acquired-dengue-cases-100-2026a1001422
2.CDC Issues Emergency Response for Florida Dengue Outbreak, by Kristina Fiore, https://www.medpagetoday.com/infectiousdisease/generalinfectiousdisease/123530
3.Dengue cases in Florida continued to climb after emergency declared, By Alex DeLuca, https://www.washingtonpost.com/nation/2026/10/23/dengue-cases-florida-continued-climb-after-emergency-declared/
4.One mosquito and the look-alike fevers that arrive with the rains, by Supriya Ramesh, https://www.newindianexpress.com/lifestyle/health/2026/Oct/22/one-mosquito-and-the-look-alike-fevers-that-arrive-with-the-rains
5.PAHO calls for strengthened surveillance and preparedness amid increases in dengue and chikungunya in the Americas, https://www.paho.org/en/news/21-10-2026-paho-calls-strengthened-surveillance-and-preparedness-amid-increases-dengue-and
Curated by Jonathan M. Metsch, Dr.P.H.
Clinical Professor of Environmental Medicine, Icahn School of Medicine at Mount Sinai