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The current dengue outbreak in Florida appears to be the largest in several decades in the continental United States.
State health officials reported this week that more than 250 locally acquired cases of the mosquito-borne disease have been counted so far this year. The vast majority were recorded in Hillsborough County, where Tampa is located.
Federal health officials note that their data on dengue outbreaks are limited. But available information from state health departments and medical journals indicates that the Florida outbreak marks the highest number of cases in a calendar year for any state since at least the 1940s.
Puerto Rico consistently suffers heavy impacts from dengue, with figures much higher than those seen in any of the 50 U.S. states. But in the continental United States, Florida typically records the highest number of locally transmitted cases. The state's worst year so far had been 2023, when just under 200 cases of local transmission were reported.
Officials in Hillsborough and surrounding counties have declared local emergencies, and workers in the Tampa area are spraying day and night to reduce the population of mosquitoes that transmit diseases.
What is dengue?
Dengue is caused by a virus spread by the bite of a type of mosquito.
Many infected people do not get sick, but some develop fever, flu-like symptoms and—notoriously—aches. It has been dubbed “breakbone fever” because of the excruciating pain some people experience. Severe cases can cause bleeding, shock, and death.
There has been one death from dengue in Florida this year: an older woman from Tampa on September 4.
There are four types of dengue viruses, known simply as 1, 2, 3, and 4. When someone is infected for the first time, their body develops lifelong antibodies against that type. If they are infected with another type of dengue, the antibodies from the first infection may not neutralize the second type and, in fact, may help the virus enter immune cells and replicate. That has made it difficult to develop an effective vaccine.
Most people in the Tampa metropolitan area have no prior immunity to any form of dengue, noted Dawn Wesson, an expert on dengue and other mosquito-borne diseases at Tulane University.
How does dengue spread?
Warm-weather mosquitoes that transmit dengue live in Florida and other hot parts of the United States, but experts say they have been expanding their geographic reach due to climate change.
For decades, most infections in the continental United States were detected among people who contracted the virus while traveling internationally, along with locally acquired cases in Puerto Rico.
But in 2009-2010, Key West, Florida, reported the first cases of dengue acquired in the continental United States outside of the Texas-Mexico border since 1945.
The largest dengue outbreak in any U.S. state since then occurred in Hawaii, where 264 locally acquired cases were reported over a six-month period in 2015-2016. The outbreak in the Tampa metropolitan area, which was first reported in July, is already on the verge of exceeding that figure.
Worldwide, more than 2.2 million infections and nearly 1,200 deaths have been reported this year, according to the World Health Organization.
There have been nearly 1,900 locally acquired cases in the United States this year, the majority in Puerto Rico, according to the Centers for Disease Control and Prevention (CDC).
Why is it so serious in Tampa?
Florida tends to see a lot of dengue in part because the state receives many travelers who have been to Puerto Rico or other places where the disease is present, explained Wesson.
Generally, most cases are concentrated in South Florida, around the Miami metropolitan area. It is difficult to say what is happening this year in the Tampa area, but the increase could be linked at least in part to travel patterns, she added.
Locally acquired cases in Florida have actually surpassed travel-associated cases, with a count of 252 versus 245 as of last week. But the difference is small, and at least 13 Hillsborough County cases were diagnosed in travelers, according to the state.
Traditionally, the CDC would have a very visible presence in a situation like this, but this time that has not been the case, Wesson observed.
The federal public health agency must be invited by state officials, and Florida authorities have not asked for CDC disease investigators to come, said CDC spokesman Jason McDonald. The agency has provided $800,000 in assistance to the state health department, he added.
[Publicidad]