Bureau of Environmental Health Services - Reportable Environmental & Occupational Diseases, Poisonings & Conditions - Harmful Algal Blooms

harmful algal blooms

Harmful Algal Blooms Surveillance Initiative

The Harmful Algal Blooms program monitors the health effects of people who come in contact with blue green algae in recreational water. The Iowa Department of Public Health works collaboratively with the Iowa Department of Natural Resources (IDNR) and CDC to expand a system that tracks and reports human illnesses related to harmful algal blooms.

What are harmful algal blooms?

Several known species of harmful algal blooms occur throughout the world. The kind most frequently found in Iowa are called blue green algae, or cyanobacteria. Cyanobacteria occur when algae that are normally present in water grow exuberantly. Within a few days, a bloom can cause clear water to become cloudy or covered in a scum layer. The cloudy or scummy water often smells bad. Algal blooms usually float to the surface and can be many inches thick, especially near the shoreline. Blue green algae often form in warm, slow moving waters that are rich in nutrients, such as fertilizer runoff or septic system overflows. Blooms can occur at any time, but most often occur in late summer or early fall. Algal blooms can appear quickly and can last a few hours, days or weeks.

Blue green algae can produce toxins that can cause people to get sick. Not all algal blooms produce toxins, however. The IDNR's Beach Monitoring program tests the water of many of Iowa's beaches and currently also tests for the presence of some toxins caused by harmful algal blooms.

What are the public health issues?

Blue green algae, or cyanobacteria, can produce toxins that can cause illnesses in people and animals. Microcystin is one of the cyabobacterial toxins that can be released from bacteria in the water during the life cycle of a blue-green algae bloom. People who accidentally swallow water or breathe in water droplets containing microcystin can develop gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. Other symptoms can include cough, runny eyes and nose, sore throat, and asthma-like symptoms. Skin rashes can also develop. In severe cases, liver failure can occur.

Is exposure to harmful algal blooms reportable?

Suspected and confirmed cases of exposure to blue green algae (microcystin poisoning) is required to be reported to IDPH by health care providers.

IDPH is specifically asking health care providers to report cases that meet the following criteria:

  • Gastrointestinal symptoms OR
  • Respiratory symptoms OR
  • Dermal symptoms OR
  • Elevated serum GGT (gamma glutamyl transpeptidase)
  • AND/Or a history of exposure within the past seven days to water testing positive for microcystin

How to report:

To report cases, please call the Iowa Department of Public Health at (800) 972-2026. This telephone line is only staffed during business hours. If you call after hours, please leave a message and your call will be returned the next business day.

What to report:

  • Health care provider's name
  • Health care provider's number
  • Patient name
  • Patient phone number
  • Patient address
  • Caller's name and phone number

Public reporting

Individuals who believe they may have become ill from exposure to blue green algae can notify IDPH by sending an email to Contact Us. The email should include the person's name and day time phone number, along with information about where and when the exposure occurred. An IDPH staff member will contact the individual to conduct a confidential telephone interview.


For More Information

  • Use the Contact Us page to submit questions online.