Surveillance for harmful algal bloom events and associated human and animal illnesses—One Health Harmful Algal Bloom System, United States, 2016—2018
Harmful algal bloom (HAB) events can result from the rapid growth, or bloom, of photosynthesizing organisms in natural waterbodies. HAB events can be exacerbated by nutrient pollution and a warming climate (1) and can negatively impact the health of humans, animals, and the environment and damage local economies (2,3). U.S. HAB events of public health concern are centered on a subset of phytoplankton: diatoms, dinoflagellates, and cyanobacteria (also called blue-green algae). CDC launched the One Health Harmful Algal Bloom System (OHHABS) in 2016 to inform efforts to prevent human and animal illnesses associated with HAB events. For 2016–2018, 18 states reported 421 HAB events, 389 cases of human illnesses, and at least 413 cases of animal illnesses. Most HAB events occurred during May–October (413; 98%) and in freshwater bodies (377; 90%). Human and animal exposures primarily occurred during June–September and May–September, respectively. Gastrointestinal or generalized signs or symptoms were the most frequently reported (i.e., >40% of human cases and >50% of animal cases); however, multiple other signs and symptoms were reported. A multidisciplinary approach to surveillance provides data about HAB events, exposures, and health effects that are critical to prevention of HAB-associated illnesses.