Florida’s red tide events tied to illness

GAINESVILLE, Fla. — Florida’s hospitals can expect an uptick in patients during red tide events, a new University of Florida Health study has found.

The research identifies red tide as a direct cause of ailments and rings the red alarm for coastal residents and tourists.

Analyzing eight years of data from Florida’s Gulf Coast, researchers found clear patterns linking red tide blooms to spikes in respiratory and stomach problems. The study is the first to move beyond association and provide evidence of causation between red tide exposure and illness.

“Our research team brought together diverse data sources on red tide and human health, allowing us to show, perhaps for the first time, that there appears to be a causal connection between these phenomena,” said Yi Guo, Ph.D., senior author of the study and associate chair for data science in UF College of Medicine’s Department of Health Outcomes and Biomedical Informatics.

A red tide occurs when algae from the species Karenia brevis blooms at concentrations that can kill marine life and make humans sick. People with asthma or compromised immune systems are especially vulnerable to contaminated air or seafood.

The research team acquired real-world clinical data and diagnoses from 137,930 individuals living along Florida’s Gulf Coast, of whom 56% were exposed to red tide. This patient data from 2012 to 2019 comes from the OneFlorida+ Clinical Research Network, coordinated by the University of Florida.

Patient records were linked with environmental data to indicate exposure to red tide. Researchers pinpointed red tide as the cause of sickness by controlling for wind patterns and many other individual factors that could have prompted visits with medical staff.

While the study could not prove that red tide causes neurological issues, it did show consistent problems for respiratory and digestive systems. The effects were stronger and more widespread when winds were blowing onshore.

The study cannot tell officials when to prepare for the next wave of illness, but the researchers did calculate that a serious red tide event could send several thousand patients to Florida’s Gulf Coast hospitals.

“Actually, the number is very big. For public health or for hospitals, it’s a big burden for them,” said Chengrong Wang, Ph.D., the journal article’s lead author and a data scientist in Health Outcomes and Biomedical Informatics.

An onshore wind may make matters worse at the beach because an expansive red tide can become aerosolized.

“Imagine a smoky bar, and if the wind is blowing the smoke toward you, you’re coughing,” said David Kaplan, Ph.D., a professor in the UF Department of Environmental Engineering Sciences and a contributor to UF’s Florida Digital Twin initiative that simulates public health threats.

Kaplan describes the red tide data obtained from the Florida Fish and Wildlife Conservation Commission as “the best in the world.” He helped the research team connect health data with the location of red tides.

“If someone is showing up with a symptom, and their ZIP code was here, what was going on with red tide and onshore winds at that time?” Kaplan said.

Red tide events occur almost every year along Florida’s Gulf Coast, with the most recent prolonged bloom in 2018. During the 2012-2019 study period, the area south of Tampa Bay showed the highest levels of toxic algae.

Wang hopes future research will investigate the long-term health effects of red tide events, and he believes this study will provide a good foundation.

“I think it will have a great impact on future studies and help protect people from the effects of red tide,” Wang said.

Other University of Florida collaborators and article authors include professor Mattia Prosperi, Ph.D., from the College of Public Health and Health Professions, and doctoral student Nicholas Chin from the Department of Environmental Engineering Sciences, as well as postdoctoral associate Andres Manrique, Ph.D., and research coordinator Kathryn Rohlwing, both from Health Outcomes and Biomedical Informatics.