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Yellow Fever Could Come Back in Florida: Experts Speculate

Updated: Jun 8

Yellow fever has a notorious history in Florida. Outbreaks devastated the state in the late 1800s, killing thousands before being eradicated in the early 20th century. 

Today, the mosquito that transmits yellow fever is common in Florida once again. With other mosquito-borne diseases like dengue and malaria occasionally spreading locally, could yellow fever also return?

Key Takeaways

  • Climate change may expand the range of yellow fever and the mosquitoes that carry it.

  • Recent dengue cases show how infected travelers can spark outbreaks.

  • Ongoing surveillance, mosquito control, and vaccination are vital to prevent yellow fever from regaining a foothold in Florida.

History of Yellow Fever in Florida

Yellow fever first struck Florida after arriving on a slave ship from Cuba. Over the next 50 years, severe epidemics erupted every 5 to 15 years, brought by ships carrying infected passengers and cargo. 

The disease quickly spread inland, transmitted by Aedes aegypti mosquitoes that breed around homes. Tens of thousands died in Florida’s 19th-century yellow fever outbreaks as the infection caused high fevers, bleeding, shock, and organ failure.

After 1900, mosquito control efforts succeeded in eradicating Aedes aegypti from Florida. No longer able to spread yellow fever, the last U.S. cases occurred in 1905. However, the persistence of yellow fever in South America and Africa meant the mosquito vector could someday reestablish itself in Florida.

By the 1980s, Aedes aegypti had returned to Florida's urban areas. Dengue fever cases also began emerging as infected travelers introduced the virus. But yellow fever hasn't yet been detected despite an extensive monkey and mosquito surveillance program. 

Additional monitoring was established along the Florida-Georgia border after isolated cases surfaced in rural Georgia and Alabama from mosquitoes occasionally infected by forest-dwelling animals. The current risk of yellow fever restarting in the U.S. is considered low but vigilance remains necessary.

Mosquito-Borne Diseases Found in Florida

Mosquito-borne illnesses are spread by mosquitoes infected with viruses or parasites. When they bite humans or animals, these pathogens can cause disease. Several Florida mosquito species transmit viruses and parasites, resulting in infections ranging from mild to deadly severity in people, horses, and other animals.

Locally acquired diseases in Florida include:

  • West Nile fever

  • Eastern equine encephalitis

  • St. Louis encephalitis

  • Dengue fever

  • Sporadic Malaria

Though not endemic, these infections could spread if travelers bring the diseases into Florida from other countries where they are endemic.

  • Chikungunya

  • Yellow Fever

  • Rift Valley fever

Florida’s Recent Increase in Dengue Cases

In 2023, Florida has already reported 10 locally acquired dengue cases and 190 travel-associated cases as of August. The locally transmitted cases in Miami-Dade and Broward counties have prompted health alerts. 

Four dengue serotypes now circulate, increasing the risk of repeat infections. While most cases are mild, secondary infections raise the specter of life-threatening complications like internal bleeding and organ impairment. There is no antiviral treatment, so patients receive supportive care only.

With over 3 million global dengue cases this year, experts attribute the rise to climate change expanding mosquito ranges. Hotter temperatures accelerate viral replication rates. Though prevention focuses on mosquito control and bite avoidance, more research into dengue vaccines and therapeutics is still needed

Could Climate Change Contribute to the Return of Yellow Fever in Florida?

Reports say that experts postulate the expansion of geographic ranges of mosquitoes and the diseases they carry due to warming global temperatures. Aedes aegypti mosquitoes and the viruses they transmit like dengue, chikungunya, Zika, and yellow fever, may become endemic farther north than their current ranges. 

Increased heat, longer summers, and urbanization are projected to increase biting, reproduction, pathogen development rates in mosquitoes and lower disease incubation times in humans.

Ongoing surveillance and mosquito control are vital to prevent yellow fever and other mosquito-borne diseases from regaining footholds in Florida. 

The public can help eliminate risks by eradicating standing water breeding sites. While the future impacts of climate change are uncertain, proactive adaptation strategies will be key to reducing growing infectious disease risks.

Get Vaccinated Against Yellow Fever

While the current risk remains low, experts advise travelers to get vaccinated against yellow fever before visiting endemic regions. 

Prior to your trip, come and talk to a travel health expert at Away Clinic. You can visit us in ScottsdaleChandler and Phoenix to get your yellow fever vaccine, or to make a good plan to stay healthy, based on where you're going and what you need.


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