Osaka-Kansai Expo to Contain Infectious Diseases with Weekly Sewage Monitoring—The Full Scope of the First "Water Footprint" Monitoring System for a Mega Event

1. Introduction: Ensuring Expo Safety with "Invisible Data"

• The Concept of Wastewater-Based Epidemiology (WBE) and Its Rise During COVID-19

• Three Sanitary Risks Facing Expo 2025

  1. High-Density Attendance and Multinational Virus Strains

  2. Tropicalization × Water Features Leading to Legionella Growth Potential

  3. Infrastructure Characteristics of an Artificial Island
     
     
     
     

2. Overview of the Monitoring System

2-1 Sampling Protocol: Once a Week × Three Locations

• Bottle sampling at the Maishima Pumping Station 3 km northeast of Yumeshima, with PCR processing within 24 hours

• Sampling day is every Wednesday. A flow correction factor is introduced to adjust for differences in visitor flow between off-peak (weekdays) and peak (holidays) periodskobe-np.co.jp

2-2 20 Pathogen Panel

• Measles, MERS, Influenza A/B, Norovirus, Enterohemorrhagic E. coli, Monkeypox Virus, etc.

• Marker genes comply with the "Standard Kit for Wastewater Pathogens" by the National Institute of Infectious Diseases

3. Data Integration Flow

1. Laboratory → Dashboard

   • Push Ct values every 12 hours via LIMS within OIPH
     
     

2. Dashboard → Expo Control Room

   • Machine learning model flags "rising trend for three consecutive days" as a red alert
     
     

3. Expo Control Room → Osaka City Public Health Center

   • Cluster response team cross-tabulates with clinic visit data

   • Simultaneously auto-post to social media in visitors' native languages (English, Chinese, Korean)

4. Differences from Tokyo 2020 Olympics

WBE at the Tokyo 2020 Village successfully detected positives 1.7 days before clinical onset.academic.oup.com. For the Expo, due to the vastly larger scale of attendees, the sample smoothing algorithm is enhanced to keep the false positive rate below 1%.

5. The "Four Assurances" Provided by Wastewater Surveillance

1. Early Warning: Signals before patients appear at fever clinics.

2. Overcoming Language Barriers: Multilingual apps display risk levels in color codes.

3. Rapid Containment: CO₂ sensor thresholds in surrounding pavilions are automatically tightened upon positive signals.

4. Urban Legacy: Permanent monitoring in the Yumeshima redevelopment area post-Expo.

6. Technical Details: From PCR to AI Analysis

• 24-well qPCR devices × 2 units, calculating Ct values in as little as 3 hours

• Metagenomics uses Oxford Nanopore GridION for real-time detection of nucleotide mutations

• Bayesian time series forecasting with AutoML on Azure

7. Challenges and Prospects

• RNA adsorption by particulate matter ⇒ variability in recovery rates

• Dilution issues due to tidal influence at observation sites

• Next generation moves to on-site loops (autonomous sensors + Edge AI)

8. International Evaluation and Ripple Effects

WHO's Mass Gathering Health Network plans to adopt the "Expo Model" as a reference case for the 2026 Milan-Cortina Winter Olympics. Australia's Brisbane 2032 will refer to the same system for its harbor-type venues.

9. Conclusion

The wastewater epidemiology at the Osaka-Kansai Expo is a practice of merging environmental data with behavioral data into a "water footprint." Both visitors and organizers step into a new era of protecting themselves from infectious diseases by listening to the "invisible voice of water."

List of Reference Articles

1. Kobe Shimbun NEXT "Infectious Disease Investigation in Sewage Around Expo Venue: Research on Measles and Other Expansion Predictions" (June 29, 2025)kobe-np.co.jp

2. Fukui Shimbun ONLINE "Infectious Disease Investigation in Sewage Around Expo Venue: Research on Measles and Other Expansion Predictions" (Same)fukuishimbun.co.jp

3. AP News "Japan’s Osaka Expo temporarily suspends water shows after high levels of bacteria detected" (June 9, 2025)apnews.com

4. Kitajima M. et al. "COVID-19 wastewater surveillance implemented in the Tokyo 2020 Olympic and Paralympic Village." Journal of Travel Medicine 29 (3), 2022. academic.oup.com