One Health Harmful Algal Bloom System (OHHABS)

One Health Harmful Algal Bloom System (OHHABS) logo

Harmful algal blooms (HABs) can contaminate the environment, drinking water, recreational water, and food.  They are an emerging public health issue. Exposure to HAB toxins through water, food, or air may cause a range of mild to severe symptoms in both humans and animals. HAB-associated exposures can result in symptoms that affect the skin, stomach and intestines, lungs, and nervous system. Animals, such as dogs, cattle, birds, and fish, are likely to be affected during a HAB event before people, as they are more likely to drink from or swim in waters that contain HABs. People can be affected by HAB events from exposure during work or recreational activities, or from ingestion of contaminated water or food.

About the One Health Harmful Algal Bloom System (OHHABS)

The One Health Harmful Algal Bloom System (OHHABS) is a voluntary reporting system available to state and territorial public health departments and their designated environmental health or animal health partners. It collects data on individual human and animal cases of illnesses from HAB-associated exposures, as well as environmental data about HABs. The goal of OHHABS is to collect information to support the understanding and prevention of HABs and HAB-associated illnesses.

OHHABS is an example of One Health surveillance. One Health is an approach that recognizes that human, animal, and environmental health are interconnected, and that human health, animal health, and environmental health communities can more effectively address many linked health challenges by working together.

OHHABS development began in 2014 as a collaborative effort between state and federal partners. In addition to state and federal expertise on HABs, CDC leveraged three essential resources to develop and launch OHHABS in June 2016:

  • Technical capability for electronic reporting via the National Outbreak Reporting System (NORS) platform.
  • Lessons learned from a previous HAB-associated illness surveillance efforts that ended in 2012.
  • Support from the Great Lakes Restoration Initiative (GLRI), which will use OHHABS data to evaluate and inform restoration efforts for the Great Lakes ecosystem.

Evidence suggests that HABs are increasing in frequency and severity due to climate change, farming practices, storm and wastewater runoff, and other environmental factors. The identification of HABs is critical to determine their patterns of occurrence, to protect water and food supplies, and to alert the general public when there is a problem.

HAB-associated outbreaks can be reported NORS. However, NORS only captures aggregate information about outbreaks, which include two or more cases of human illness. Surveillance for HAB-associated cases of human and animal illnesses will provide additional information on the number of cases occurring each year, where illnesses are occurring across the United States, and symptoms in humans and animals from exposure to HABs. These data will help to better define the effect of HABs on humans, animals, and the environment.

Although OHHABS and NORS and share web-based reporting features, each system captures different types of data for HAB-associated illnesses and events. OHHABS is an event-based reporting system for HAB events and individual human and animal cases of HAB-associated illness. NORS is an event-based reporting system for foodborne, waterborne, and enteric disease outbreaks that may collect HAB-associated aggregate outbreak data (i.e., summary data describing two or more people). A HAB-associated outbreak can be reported in both OHHABS and NORS; however, data are collected differently in each system.

comparison circle between NORS and OHHABS.

What Can Be Reported in OHHABS?
Harmful Algal Bloom Events Location and description of a HAB in any water body (e.g., inland lake, coastal water body, brackish water body)

For foodborne HAB-associated illnesses with no observed HAB event, the most likely food source (e.g., seafood catch or harvest location) may be reported.

Human Cases of Illness Individual cases of human illness

Note: If multiple people became ill following exposure to a HAB, state and territorial public health partners should submit both OHHABS and NORS reports.  NORS is used to report at the level of an outbreak (≥ two persons linked epidemiologically by time, place, or exposure). Data are reported to NORS in aggregate; data are reported to OHHABS for individual cases.

Animal Cases of Illness Individual cases of animal illness

Domestic pets (e.g., dogs, cats, parrots, guinea pigs)

Livestock (e.g., cattle, sheep, goats, chickens, pigs, horses)

Wildlife non-domesticated animals (e.g., birds, sea lions, fish, deer)

Note: Animal cases of illness can be reported individually (e.g., single dog, single sea lion) or at the group level for multiple animal cases (e.g., a fish kill, a herd of cattle, a flock of birds). Users can indicate whether they are reporting a single case or a group of animal illnesses.

OHHABS is intended for use by public health departments and their designated environmental health and animal health partners.

If you are a public health professional, an environmental health professional, or an animal health professional interested in reporting to OHHABS, please contact your state’s OHHABS Reporting Site Administrator (RSA) to gain access. For assistance on identifying or contacting your state’s OHHABS RSA, please contact

If you are a member of the general public and would like to report a HAB-associated illness or event, please contact your local or state health department. Contact information can be found at the Public Health Professionals Gateway: State & Territorial Health Department Websites.

CDC has developed a partner toolkit to help public health professionals inform the public, community leaders, and others interest groups about HABs and OHHABS. The toolkit includes an OHHABS fact sheet, template newsletter article, template slide deck for OHHABS training activities, and a HAB resources sheet.

CDC also has resources to inform the public, physicians, and veterinarians about HAB-associated illnesses. These include a fact sheet, poster, and reference cards. Please visit our Health Promotion Materials page to download these materials.

The forms on this page are intended for use by staff at local, state and territorial agencies that report to OHHABS. The forms are available as either static (print out for hand written completion) or dynamic (electronically fillable pdfs). These forms can be used by staff in jurisdictions that do not have direct access to OHHABS; the forms may assist in collecting the information that can be entered into OHHABS by staff that do have access (e.g., at the state level).

Static Forms


Fillable Forms

Page last reviewed: October 15, 2019