Neurological illnesses associated with Florida red tide (Karenia brevis) blooms.

•Brevetoxins are produced by the marine harmful alga, Karenia brevis (K. brevis); and humans can be exposed to these toxins through a variety of pathways, including inhalation of aerosols and consumption of toxin-contaminated seafood;•Neurological illnesses may also be associated with human exposures to brevetoxins, but to date there has been little research on this specific effect;•During K. brevis blooms in nearby coastal waters, significant increases in visits to emergency departments by older coastal residents (≥55 years) were found specifically for the primary diagnosis of headache (ICD-9 784.0);•In previous studies, older coastal residents were also at increased risk for respiratory illnesses associated with K. brevis blooms;•Preventive measures designed to reduce and limit human exposures to brevetoxins are recommended; and healthcare providers should be instructed to consider brevetoxin exposures and resultant neurological illness as possible diagnoses.