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Physician Information

Many Ohioans spend their weekends recreating in and around our state’s lakes, rivers and streams.  Few are aware of the potential for Harmful Algal Blooms (HABs) which could make them sick.

“Screen for Green” is a new Ohio Department of Health program to help busy providers like you identify potential patients with HABs exposure.

HABs are groups of cyanobacteria which can produce illness causing toxins. Symptoms can include gastrointestinal (nausea), neurologic (dizziness) and skin rashes. Severe disease can result in neuro, nephro- and hepatotoxicity depending on the toxin.

For patients presenting with ill-defined GI, neuro or skin symptoms AND a recent history of recreating in a waterway, consider HABs toxin exposure. Refer to the “screen for green” algorithm and fact sheet link below.  Treatment of HABs illness largely involves providing supportive care.

The early identification and reporting of HABs illnesses to public health is critical to reducing additional HABs illnesses in affected recreational waters.  To report a HABs illness, contact the Local Health District Epidemiologist or the Ohio Department of Health.  Contact information for local health districts can be found here.   

Below are some facts about HABs

  • HABs may occur in recreational waters throughout Ohio.
  • Cyanobacteria in HABs are typically green or red colored and can sometimes be seen on the water surface.
  • Cyanobacteria can migrate in the water column so any water depth can contain toxins.
  • Even if you don’t see a bloom or surface scum doesn’t mean that toxins aren’t present.
  • Even a small amount of swallowed HABs-contaminated water can cause symptoms.
  • Symptoms typically occur within 48 hours.

ODH operates a beach monitoring program that includes BeachGuard, a website listing public beaches and other recreational waters where known toxin advisories are posted around Ohio.

The Ohio Department of Natural Resources and Ohio Environmental Protection Agency monitor state-run beaches and boat ramps for HABs. Private waterways are not routinely monitored, although some voluntarily participate in BeachGuard.  More information on HAb monitoring can be found at the State of Ohio Algae webpage.

Physician-Specific Information

"Screen for Green" Physician factsheet

"Screen for Green" treatment algorithm/flowchart

"Screen for Green - Diagnosing Harmful Algal Bloom Illness" Video 

HAB Illness Report Form - Private Water Systems 

HAB Illness Report Form - Recreational Waters


Helpful Links

ODH Beachguard

Ohio Algae Information for Recreational Waters

CDC Harmful Algal Bloom Illness

USEPA Harmful Algal Bloom Information


Page Updated: 6/28/2018