Filling Surveillance Gaps: Crowdsourced Evidence of Human Health Impacts During an Unprecedented Harmful Algal Bloom in South Australia — The Association Specialists
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  3. Filling Surveillance Gaps: Crowdsourced Evidence of Human Health Impacts During an Unprecedented Harmful Algal Bloom in South Australia

Filling Surveillance Gaps: Crowdsourced Evidence of Human Health Impacts During an Unprecedented Harmful Algal Bloom in South Australia (23636)

Jacqueline Stephens 1 , James Daniel 2 3 , Amy McLennan 4 5
  1. Flinders Health and Medical Research Institute, Flinders University, Adelaide, SA, Australia
  2. Institute for Sustainability, Energy and Resources, Adelaide University, Adelaide, SA, Australia
  3. Center for Disaster Management and Risk Reduction Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany
  4. School of Medicine, Adelaide University, Adelaide, SA, Australia
  5. School of Cybernetics, College of Systems and Society, Australian National University, Canberra, ACT, Australia

Background: Since March 2025, South Australia has experienced an unprecedented harmful algal bloom (HAB) involving Karenia mikimotoi and Karenia cristata, with the latter marking the first detection of brevetoxin in Australian oysters. While social media wa flooded with widespread health complaints among beachgoers, official surveillance systems reported no increase in hospital admissions or Emergency Department presentations. This discrepancy created a critical gap between lived community experience and formal health data. To address this, researchers developed the Algal Bloom Shed health survey to systematically capture real-world human health impacts during the event.

Methods: An anonymous, GDPR and APP compliant, self-reporting health data portal was launched on 24 November 2025. The community-informed survey collects basic demographics (age, sex), exposure information (location, date), and treatment (medical consultation, medications).

Results: Of the 235 human reports, 75.7% were female and 60.0% were aged 40 to 69 years. Predominant symptoms were scratchy cough (58.7%), sore throat (48.5%), and breathing difficulties (24.3%). Nearly half (49.8%) of respondents used medications for symptom relief, and 33.2% sought medical consultation. Despite the lack of hospitalizations, 20 respondents specifically reported impacts on their psychological wellbeing.

Conclusion: While public discourse often focused on brevetoxins, the survey findings suggest symptoms experienced by South Australian beachgoers are consistent with respiratory and mucosal irritation by aerosolized biological fragments, rather than systemic poisoning. Crowd-sourced data proved vital for validating community experiences that traditional metrics, like hospitalizations, failed to capture. This study demonstrates that volunteer-led surveillance can fill essential gaps when traditional data collection systems do not detect an uptick in acute presentations. Future public health strategies should focus on empowering communities to make personal risk assessments based on marine and weather conditions. Sustained funding is required to investigate potential long-term health consequences of HAB.