In 2021, the Centers for Disease Control and Prevention (CDC) recorded 368 harmful algal bloom (HAB) events across 16 states through the One Health Harmful Algal Bloom System (OHHABS). These HAB events, characterized by the rapid growth of algae or cyanobacteria in water bodies, resulted in 117 human cases of illness and over 2,715 animal cases. With peaks during the summer months and substantial public health, economic, and environmental implications, HABs underscore the importance of a collaborative One Health approach.
OHHABS is a surveillance system that enables public health agencies and their environmental and animal health partners to voluntarily report HAB events and related illness data across various U.S. territories. The term HAB event encompasses the identification of an algal bloom or detection of toxins in water or food. Human illness reports are individual, while animal illness reports can include groups, such as flocks of birds. This data aids in public health prevention efforts.
HAB event data includes observation dates, geographic information, and water characteristics like salinity and color. Demographic information, exposure details, symptoms, and health outcomes are reported for illnesses. In 2021, the CDC standardized data quality checks and redefined their methodology, ensuring positive detections required concentrations greater than zero. Missing data for animal groups were approximated for more accurate descriptive analysis.
Timing and Classification: HAB events were predominantly reported during summer, peaking in August (92 events, 25%). A majority of HABs (311, 85%) were confirmed. Human illnesses occurred primarily in June (38 cases, 33%), and animal illnesses peaked in August (2,328 cases, 86%). Most human illnesses were probable (89%), while animal cases were confirmed (74%).
Symptoms and Impact: In humans, common symptoms include gastrointestinal, generalized (e.g., headache, fever), and dermatologic issues. For animals, generalized symptoms (e.g., lethargy) and gastrointestinal problems dominated, particularly in domestic pets. Wildlife was significantly affected, with a mortality event resulting in over 2,000 bat deaths.
The CDC’s OHHABS data from 2021 reveals significant health impacts due to harmful algal blooms. By leveraging a One Health approach, this surveillance system provides crucial insights into mitigating future HAB events’ effects on human and animal health. Readers can refer to the OHHABS data webpage or the CA HAB Portal for detailed data and further information.
Harmful algal blooms (HABs) pose significant public health, environmental, and economic challenges. Managing and mitigating these issues requires a combination of regulatory, scientific, and community-based strategies. Here are critical methods for addressing HABs:
Agricultural Practices: Implementing sustainable farming techniques, such as cover cropping, crop rotation, and reduced fertilizer application, can help lower nutrient runoff into water bodies. Using buffer strips and wetlands between farmland and waterways further reduces nitrogen and phosphorus loading.
Urban Runoff: Improving stormwater management in urban areas through green infrastructure, like rain gardens and permeable pavements, helps reduce excess nutrient input.
Wastewater Treatment Improvements: Upgrading wastewater treatment plants to remove more nutrients before effluent discharge can prevent nutrient pollution. Preventing illicit sewage connections or septic system leaks is critical to protecting water quality.
Applying algaecides (chemical treatments) or using biological controls, such as specific fish species that feed on algae, can help directly control blooms. However, this method should be used cautiously to minimize unintended ecological consequences.
Regular monitoring of water quality and algal blooms, combined with predictive modeling, can help detect potential HABs early. Implementing real-time monitoring systems in vulnerable areas aids in issuing timely public health alerts.
Educating the public on how their activities impact water quality can motivate behavior changes, such as minimizing lawn fertilizer usage or maintaining septic systems. Collaboration between government, industries, NGOs, and communities ensures a coordinated response.
Stronger regulations and policies, such as watershed management plans and nutrient reduction strategies, are essential. Support from local and national governments is vital for enforcing these guidelines and incentivizing good practices.
Restoring wetlands, riparian buffers, and coastal areas can help absorb excess nutrients, serving as natural filters. The re-establishment of these habitats improves ecosystem resilience to HABs.
Addressing HABs requires a multifaceted approach encompassing scientific research, policy implementation, and community engagement. These comprehensive strategies can reduce the occurrence and impact of harmful algal blooms, helping safeguard human health and aquatic ecosystems.
