ABSTRACT
The 2020 Olympic/Paralympic Games have been postponed to 2021, due to the COVID-19 pandemic. We developed a model that integrated source-environment-receptor pathways to evaluate how preventive efforts can reduce the infection risk among spectators at the opening ceremony of Tokyo Olympic Games. We simulated viral loads of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emitted from infectors through talking/coughing/sneezing and modeled temporal environmental behaviors, including virus inactivation and transfer. We performed Monte Carlo simulations to estimate the expected number of newly infected individuals with and without preventive measures, yielding the crude probability of a spectator being an infector among the 60,000 people expected to attend the opening ceremony. Two indicators, i.e., the expected number of newly infected individuals and the newly infected individuals per infector entry, were proposed to demonstrate the extent of achievable infection risk reduction levels by implementing possible preventive measures. A no-prevention scenario produced 1.5-1.7 newly infected individuals per infector entry, whereas a combination of cooperative preventive measures by organizers and the spectators achieved a 99% risk reduction, corresponding to 0.009-0.012 newly infected individuals per infector entry. The expected number of newly infected individuals was calculated as 0.005 for the combination of cooperative preventive scenarios with the crude probability of a spectator being an infector of 1 × 10-5. Based on our estimates, a combination of cooperative preventions between organizers and spectators is required to prevent a viral spread at the Tokyo Olympic/Paralympic Games. Further, under the assumption that society accepts < 10 newly infected persons traced to events held during the entire Olympic/Paralympic Games, we propose a crude probability of infectors of < 5 × 10-5 as a benchmark for the suppression of the infection. This is the first study to develop a model that can assess the infection risk among spectators due to exposure pathways at a mass gathering event.
ABSTRACT
BACKGROUND: Risk communication is widely accepted as a significant factor for policy makers, academic researchers, and practitioners in diverse fields. However, there remains a lack of comprehensive knowledge about how risk communication is currently conducted across fields and about the way risk communication is evaluated. METHODOLOGY: This study systematically searched for materials from three scholarly search engines and one journal with a single search term of "risk communication." The eligibility assessment selected peer-reviewed articles published in English that evaluated risk communication activities. Emphasis was placed on articles published in recent years accounting for about half of the pre-selected ones. Data on field of study, intervention timing, target audience, communication type, and objectives/evaluation indicators was extracted from the articles. Patterns of objectives/evaluation indicators used in risk communication activities were compared with those of the definitions and purposes of risk communication stated by relevant organizations. Association analysis was conducted based on study fields and objectives/evaluation indicators. RESULTS: The screening process yielded 292 articles that were published between 2011 and 2017 in various fields, such as medicine, food safety, chemical substances, and disasters/emergencies. The review process showed that many activities were performed in the medical field, during non-/pre-crisis periods. Recent activities primarily targeted citizens/Non-Profit Organizations (NPOs), and was disseminated in the form of large group or mass communication. While "knowledge increase," "change in risk perception and concern alleviation," and "decision making and behavior change" were commonly addressed in practice, "trust-building" and "reduction in psychological distress" were rarely focused. The analysis also indicated that the medical field tends to perform risk communication at the individual or small group level, in contrast to the food safety field. Further, risk communications in the non-/pre-crisis period are more likely to aim at "changes in risk perception and concern alleviation" than those in the crisis period. Risk communications that aim at "changes in risk perception and concern alleviation" are likely to be presented in a large group or mass communication, whereas those that aim at "decision making and behavior change" are likely to be conducted at the individual or small group level. CONCLUSION: An overview of recent activities may provide those who engage in risk communication with an opportunity to learn from practices in different fields or those conducted in different intervention timings. Devoting greater attention to trust building and reduction in psychological distress and exploring non-citizen/NPO stakeholders' needs would be beneficial across academic and professional disciplines.