(NEW YORK) — As cases of dengue fever continue to rise in Florida, public health specialists are worried the true number of infections may be greater.
For the week ending Sept. 19, at least 190 cases of locally acquired dengue have been confirmed in the state, an increase of 38 cases from the week before, according to data from the Florida Department of Health (DOH).
Hillsborough County, which includes Tampa, is reporting the highest number of cases at 170 followed by Miami-Dade, Orange, Palm Beach, Pasco and Pinellas counties, DOH data shows.
“There’s evidence of local transmission of dengue in several counties in Florida,” Natalie Dean, an associate professor of biostatistics and informatics at Emory University’s Rollins School of Public Health, told ABC News. “Dengue is not endemic to the United States. That means that it doesn’t typically cause local transmission.”
She added, “There can be occasional outbreaks in the U.S. but this one is notable for its size.”
Last week, DOH reported the state’s first death from dengue fever this year but did not provide any details about the patient including name, age, sex or residence.
Three counties — Hillsborough, Pasco and Pinellas — declared local states of emergency last week. These allow local governments to waive normal procedures, access emergency resources and strengthen efforts to control mosquito populations.
Pinellas County crews have been going door to door and spraying areas with high mosquito presence, according to local ABC News affiliate WFTS.
“I don’t recall a [period] of time when it’s been this high in such a sort of concentrated area before,” Cameron Wolfe, an infectious diseases specialist and a professor of medicine at Duke University School of Medicine, told ABC News.
Wolfe said there may be an underestimate of the true number of cases in Florida. Cases of dengue can be mild, and people may recover on their own or never be tested. Because dengue can resemble a flu-like illness, patients may never suspect the source of their infection.
Additionally, he said that reporting of confirmed cases to either local state departments or the CDC can lag.
“For every case that we know, there’s going to be a bunch that we never find out about,” Wolfe said.
Dean added that people can be infected with dengue multiple times over the course of their life, but it’s usually the second or later infection that is more severe, leading to further underreporting.
“I always think of like the top of an iceberg,” Dean said. “We’re only capturing some of the some of the cases.”
The Centers for Disease Control and Prevention (CDC) told ABC News in a statement on Tuesday that the agency is “closely tracking dengue activity” and the “unprecedented” number of cases in the Tampa area.
The CDC also said they’ve provided $800,000 in emergency funds to help with the response.
“Because the types of mosquitoes that spread dengue, Aedes aegypti, are common throughout many areas of the United States, continued local spread of dengue is possible,” the CDC statement said. “The best way to prevent dengue is to protect yourself from mosquito bites by using EPA-registered insect repellant, wearing loose fitting clothes, and controlling mosquitoes in and around your home, such as dumping water.”
Some research has shown that climate change could be expanding the geographic range and severity of dengue fever.
Rising global temperature coupled with more rainfall and humidity — leading to standing water pools that serve as breeding grounds for mosquitoes — could increase the number of cases.
“Global warming and climate change, in fact, leave places like Florida more wet and more capable of housing these mosquito vectors, so I wouldn’t be surprised if this becomes a little more of a perpetual thing,” Wolfe said.
ABC News’ Youri Benadjaoud contributed to this report.
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