A massive earthquake would occur even under the pandemic of coronavirus disease 2019 (COVID-19); therefore, it is necessary to estimate the impacts of complex disasters like this and it prepare for these in advance. Since COVID-19 has been caused outbreaks in closed and dense spaces, there is a concern that the infection may spread at shelters during the Nankai Trough Earthquake. Furthermore, after the massive earthquake, it is expected that the infected people will not receive adequate medical care due to the collapse of medical care system by physical damage of the facilities and increase in medical demand from injured people. Therefore, in this study, the outbreak of infection and bed shortages were estimated based on the Susceptible-Infected-Recovered (SIR) mathematical model to address the prevention of medical collapse in the earthquake. As a result, it was found that the maximum shortage of hospital beds would be 266, 000 beds and the maximum shortage period would be 350 days.

This study examined the effects of knowledge on infectious disease preventive behavior, risk perception, and responsibility for the ripple effects of infection. The ripple effect of infection implies that an individual is infected with an infectious disease and then infects another person, with the result that the infection spreads further, and various effects are exerted on society. The more strongly an individual has the expectation of responsibility for the ripple effect, the more likely the individual will take preventive action. Similarly, the amount of the knowledge has a promotive effect on preventive behavior, while risk perception is expected to have a weaker influence. Based on the above predictions, a web-based survey was conducted during the period of the spread of COVID-19. Data obtained from 1238 people were analyzed by classifying them into two regions according to the time when the state of emergency was issued. The results indicated the main effect of knowledge and sense of responsibility was significantly positive influence on preventive behavior regardless of the region. In addition, the interaction between knowledge and sense of responsibility was significant; the effect of sense of responsibility became stronger when knowledge was low. The importance of knowledge and sense of responsibility for infectious disease prevention behavior is discussed.

Structuring the topics of risk-related articles is expected to lead to understanding the characteristics of various risk sciences. Here, we used structural topic modeling to analyze the topics of risk-related articles, and compared each topic with the content of the encyclopedia of risk research. The target journals were Risk Analysis (RA), Journal of Risk Research (JRR), and Science published up to 2020. For RA and JRR, all articles were included, and for Science, articles that included risk in the title, abstract, or keywords were selected. 3761 RA articles, 1403 JRR articles, and 947 Science articles were included. Articles were classified based on the co-occurrence of terms used in the abstract. The 23 classified topics can be divided into three types of topics: risk events, risk analysis approaches, and risk sociality and communication. RA and JRR contained more articles on topics related to risk analysis approaches and risk sociality and communication in general, while Science included more articles on topics such as “diseases and genes.” In comparison with the encyclopedia, chapters 1–4 of the encyclopedia corresponded to topics on risk analysis approaches and risk sociality and communication, and chapters 6–9 corresponded to topics on risk events. The encyclopedia also had other chapters on finance and other topics. On the other hand, there was no chapter in the encyclopedia corresponding to the topic of “diseases and genes.” Analyzing the risk science by structural topic modeling can provide useful knowledge for overviewing the risk science fields and preparing the next encyclopedia.