COVID-19, which originated in Wuhan, China, 2 years ago, became a pandemic, that continues to this day.

The Journal of Disaster Research (JDR) edited a special issue, “Special Issue on COVID-19 and Historical Pandemics” at the end of 2020 and an electronic version of the issue was published in January 2021 (JDR Vol.16, No.1, pp. 1-117).

Even though one year has passed, life has not yet returned to normal due to the continued spread of COVID-19. Although the percentage of the general public that has been vaccinated continues to increase and various drugs and treatments have been developed, the number of COVID-19 cases also continues to increase. A huge number of COVID-19 cases have been reported, especially in Europe and the Americas.

Accordingly, we planned to publish Special Issue Part 2 and called for papers.

This Special Issue Part 2 includes 18 manuscripts, which deal with general epidemiology, effects on socioeconomic or educational areas, and clinical medicine, including vaccines and medical treatments.

The virus spike protein plays an important role in its intrusion into human cells and the onset of COVID-19 infection. Although SARS-CoV-2 (the pathogenic virus of COVID-19) originated in Wuhan, China, various variant strains with mutation in gene coding in the spike protein have appeared in multiple countries. The WHO classifies these variants into the categories of VOC (variant of concern), VOI (variant of interest), or VUM (variant under monitoring).

The definitions of VOC and VOI are as follows. VOC: “A SARS-CoV-2 variant that meets the definition of a VOI and, through a comparative assessment, has been demonstrated to be associated with one or more changes in the degree of global public health significance.” VOI: “Increase in transmissibility or detrimental change in COVID-19 epidemiology, increase in virulence or change in clinical disease presentation, or decrease in effectiveness of public health and social measures or available diagnostics, vaccines and therapeutics.”

The WHO uses Greek letters designating the variants. Accordingly as they have appeared, variants have been designated as alpha (α: the UK variant), beta (β: the South Africa variant), and delta (δ: the Indian variant).

After the deadline for the manuscript of this special issue, a new variant, omicron (o) originated in South Africa and Botswana, and it immediately began spreading worldwide. Unfortunately, it was impossible to include the manuscript on the omicron variant in this Special Issue Part 2, as the deadline had already passed.

As COVID-19 continues to spread, the JDR will plan to edit Part 3 of this COVID-19 special issue.

Following the online publication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome in January 2020, two lipid nanoparticle-encapsulated mRNA vaccines, BNT162b2 and mRNA-1273, were rapidly developed and are now being used worldwide to prevent coronavirus disease 2019 (COVID-19). The mRNA of both vaccines encodes the full-length spike protein of SARS-CoV-2, which binds to the host cell receptor angiotensin-converting enzyme 2 and is believed to mediate virus entry into cells. After intramuscular injection of the vaccine, the spike protein is produced in the cells. Both humoral and cellular immune responses to the spike protein are elicited for protection against COVID-19. The efficacy of the two mRNA vaccines against COVID-19 with wild-type SARS-CoV-2 is more than 90% and is slightly decreased with the Delta variant, which is currently the predominant variant in many countries. In this review, the effectiveness of and immune responses to COVID-19 mRNA vaccines and their mechanisms are summarized and discussed. Potential waning immunity and an additional dose of COVID-19 mRNA vaccines are also discussed.

COVID-19 has been prevalent worldwide since 2019. Increasing COVID-19 vaccination coverage is an important measure to combat the disease. An online survey was conducted with university students and personnel who were vaccinated against COVID-19 at a mass vaccination event to examine the factors promoting vaccination among young adults. The online survey was conducted with persons vaccinated at Okayama University from June 5 to September 27, 2021. Although the number of those who had fever >37.5°C increased after the second vaccination compared to the first, the vaccinated persons got more satisfied after the second shot.

This study aimed to capture aspects of Indonesian family life during a year of the COVID-19 pandemic. Data collected through online questionnaire survey, followed by 1048 participants with wide-ranged socio-economic status. The COVID-19 pandemic expands the vulnerability of families, brings economic pressure, symptoms of stress, disrupts food security and psychological welfare. However, the family tries to overcome and balance it by managing resources and increasing interaction and worship. They believe they can overcome problems, accompanied by the belief that the pandemic is a trial from the Almighty. An interesting finding was that during a pandemic, many families were stepping up their donations. The important findings of this study are the higher the stress level, the lower the social welfare, psychological welfare, and family resilience. Meanwhile, the social and psychological welfare of the family is positively influenced by the welfare of the child. Family resilience is directly and positively influenced by food coping strategies and social welfare, but is negatively affected by perceived stress symptoms. Economic pressures lead to higher social welfare which is manifested by better communication, decision making, donation, and family time management. The findings of this survey show the importance of families managing stressors and increasing family resilience.

No other infectious disease that has had a long-lasting impact on humanity in recent times has caused as much hardship as the coronavirus disease, COVID-19. While several cross-sectional surveys have reported the effects of the pandemic on daily life, there have been very few longitudinal reports from Japan. Therefore, we conducted web-based questionnaire surveys 131 and 610 days after the first case of COVID-19 infection was reported in Japan. There were 244 and 220 participants in the first and second surveys, respectively. The percentage of participants who felt stressed increased from 76 to 97% from the first to the second survey, while the frequency of going out and playing sports/exercising did not change. Regarding the problems faced due to COVID-19, the number of people who mentioned the word “stress” increased significantly in the second survey. The changes in perceived stress under difficult circumstances over a period of time can aid prediction and support during the COVID-19 pandemic in the future.

Background: Countermeasures against COVID-19 outbreak, such as lockdowns and voluntary restrictions against going out, adversely affect human stress and depress economic activity. Particularly, this stress might lead to suicide. Object: We examined excess mortality attributable to COVID-19 related suicide. Method: We applied the National Institute of Infectious Diseases (NIID) model to suicide deaths, by gender, throughout Japan during October 2009–January 2021. Effects of the great earthquake that struck eastern Japan on March 11, 2011 were incorporated into the estimation model. Results: Significant excess mortality from suicide was found during July–January for both genders. Its frequency was higher among females than among males. In total, 2276 cases of excess mortality were identified. Discussion and Conclusion: Excess mortality during the four months was more than twice that of COVID-19 deaths confirmed by PCR testing. Countermeasures against COVID-19 should be chosen carefully in light of suicide effects.

Background: No remarkable excess mortality attributable to COVID-19 has been observed in Japan until the delta strain of COVID-19 emerged. Object: We sought to quantify high pathogenicity of the delta strain using the National Institute of Infectious Diseases (NIID) model. Method: We applied the NIID model to deaths of all causes from 1987 up through August 2021 for the whole of Japan. Results: Results in Japan show 4105 excess mortality in August 2021 in Japan. It was estimated as 3.8% of the baseline. Discussion and Conclusion: We found substantial excess mortality since the outbreak of COVID-19 had emerged in August 2021, in Japan. It might be due to spread of delta strain at that time.

With the passage of almost two years since the outbreak of COVID-19, the characteristics of the infection have become clearer. It is now known that the peaks of infections recur approximately every four months, the probability of infection varies greatly by region, and the probability of infection correlates with population density.

We are still in the early stage of 21st century and the two pandemics Spanish flu and COVID-19 are the presentative pandemics in 20th and 21st centuries, respectively. The Spanish flu pandemic raged from 1918 to 1920, just after World War I. It was the first influenza pandemic worldwide; since then, humankind has experienced many such pandemics. Spanish flu is caused by a virus. However, since virology was not well established at that time, the new clinical system was needed to cope with “unknown pathogen”; during the pandemic, high infection rates were recorded, but our predecessors managed to somehow tackle the situation. With respect to the ongoing COVID-19 pandemic, both the virus and its genome were clarified quickly. Nonetheless, it has turned out to be quite an intriguing infectious disease, with the high rates in developed countries, such as the US and those in Europe, which have aging societies, and low rates in developing countries such as those in Africa, where the population is largely young. Here, I compared and discuss the two pandemics, COVID-19 and Spanish flu.

Coronavirus disease 2019 (COVID-19), a new, infectious, pneumonia-like disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has continued to spread rapidly worldwide, even in 2021. The COVID-19 outbreak has brought about some changes in influenza and respiratory syncytial virus (RSV) and rhinovirus infections, which were previously the main causes of viral pneumonia. This review discusses the epidemiology of these infectious diseases during the COVID-19 pandemic. Although influenza cases have been substantially decreasing worldwide, RSV infection cases, which had temporarily decreased initially, have started to increase again, and rhinovirus infection cases have been reported to be higher than usual. The authors reviewed the viral interferences among these infections in detail because they could exert considerable effect on epidemiological surveillance data. Based on experimental data, a recent study suggested that the influenza virus could promote SARS-CoV-2 infectivity. A previous study reported that influenza A virus inhibits RSV replication in an animal model. Another recent study revealed that although the replication of rhinovirus is not affected by SARS-CoV-2, the replication of SARS-CoV-2 is inhibited by rhinovirus, indicating that rhinovirus infection protects against SARS-CoV-2. Further studies are required to confirm these findings and evaluate the impact of SARS-CoV-2 on the activity of these viruses.

Coronavirus disease (COVID-19) patients with periodontal disease have an 8.8-fold higher mortality rate than those in the patients without periodontal diseases. This was higher than the odds ratio for patients with diabetes. Periodontal disease is associated with ulcers in the periodontal pocket, and gram-negative bacteria called periodontal pathogens invade the tissue through ulcers. Bacteria in the ulcer site are phagocytosed and sterilized by leukocytes. Following the autolysis of leukocytes, lipopolysaccharides (LPS) on the bacterial cell wall spread throughout the body, which is a major cause of multiple organ failure. Thus, periodontal disease is considered to contribute to the mortality rate of COVID-19. Ulcers in the periodontal pocket can be repaired using by a new developed brushing method called the toothpick method. The toothpick method can significantly improve gingival bleeding in one week, which is quicker than conventional periodontal treatment methods. Mechanical stimulation by the toothbrush causes gingival basal cells, fibroblasts, vascular endothelial cells and osteoblasts to proliferate and repair the tissue. However, these cell proliferations cease to occur 0.5 mm away from where the toothbrush bristles make contact with the gingiva. The toothpick method of brushing is characterized by its ability to stimulate the interdental gingiva, which is the initial site of periodontitis. As the toothpick method can repair periodontal ulcers, it will strengthen biological defense mechanisms against chronic degenerative and infectious diseases.

In this article, the authors explain how Division of Health and Welfare, the Okayama Prefectural Government, addressed the COVID-19 pandemic by focusing on the public health administration, policies enforcement, and government measures to ease the burden of people and industry, especially the hospital industry.

The coronavirus disease has caused an ongoing pandemic worldwide since 2019. To slow the rapid spread of the virus, many countries have adopted lockdown measures. To scientifically determine the most appropriate measures and policies, agent-based simulation and modeling techniques have been employed. It can be challenging for researchers to select the appropriate tools and techniques as well as the input and output parameters. This study conducted a bibliometric analysis, especially a co-word network analysis, to classify relevant research articles into five clusters: conceptual, economic-based, organizational, policy-based, and statistical modeling. It then explained each approach and point of concern. Through this, researchers and modelers can identify the optimal approaches for their agent-based models.

The spread of the novel coronavirus infection (COVID-19) has had a significant impact on the working population. Companies have been forced to respond to their employees and improve their work environment. In addition to the impact on able-bodied people, there has been a significant one on the employment of people with disabilities. This study reviews the current employment status of people with disabilities during COVID-19 and discusses the changes therein and the role of supporters in light of the changes in work styles during the pandemic. The results of the review indicate that natural disasters such as infectious diseases are difficult to predict, and concrete measures must be taken daily to maintain the safety and security of people with disabilities. People with schizophrenia especially need to prepare in normal times, since not only cognitive functions but also psychological factors will affect their acquisition of skills. Based on the characteristics of disabilities, it is crucial to support people with disabilities in normal times for them to act independently in times of disaster. Considering that natural disasters caused by infectious diseases will continue to occur, we should prepare for remote employment, training, mental health care counseling, and response during ordinary times to protect people with disabilities, along with their supporters, assuming that they may become victims.

The COVID-19 pandemic continues to pose a global threat. It is considered a CBRNE (chemical, biological, radiological, nuclear, explosive) disaster that has caused not only a public health crisis but also psychological, social, and economic problems. The recovery of social and economic activities remains an urgent issue. This study developed an assessment framework of the “recovery calendar” to visualize the process of people’s recognition of recovery from the COVID-19 calamity. Data on this recovery calendar were collected from an online questionnaire survey administered on a total of 449 respondents from 10 groups divided by gender (male or female) and age (20s, 30s, 40s, 50s, 60s, and above). The results showed that the recovery process took place in the following order: recognition of COVID-19’s impact on society and of the imposition of a constrained lifestyle, recognition of returning to work or the resumption of local schools, and finally, recognition of the recovery of the household and local economies, although these remained at a low level of activity. Importantly, the recovery progressed slowly. The results also indicated that measures such as the declaration or lifting of the state of emergency, or the “Go To” travel campaign, affected people’s recognition of recovery. Moreover, the recognition of recovery depended on social demographics. Men, younger people, and those with a stable life base were more likely to perceive recovery from the disaster. This study discussed the applicability of the assessment framework of the recovery calendar to visualize people’s recovery process from the COVID-19 calamity.

The effects of COVID-19 measures on the quantitative changes in atmospheric substances associated with economic activities have been explored in various studies. However, the specific relationship between the changes in economic activities due to government interventions and the associated changes in atmospheric substances remains unclear. This relationship needs to be understood in detail, especially in the tourism industry where conflicting responses are needed, such as promoting people flow and socioeconomic development while adopting measures to prevent the spread of infectious diseases. Therefore, this study focused on the tourism industry in Japan, used Google Earth Engine to calculate the changes in five atmospheric substances before and during the government’s Go To Travel Campaign, which was implemented to support domestic travel, and analyzed the correlations with statistical data such as the number of travelers, use of buses, and taxis. As a result, a series of connected behaviors clarified the fact that socioeconomic activities affected by the government’s Go To Travel Campaign surfaced with the changes in the atmospheric substances. To further understand the relationship between interventions to promote tourism and air quality, additional datasets and approaches are needed, including data on the operation status of facilities and the behavioral characteristics of Japanese travelers.

This study investigated the psychological conditions of Chinese international students in Japan during the COVID-19 pandemic, and the association between different forms of social capital and psychological outcomes (i.e., worries about being infected, subjective wellbeing, loneliness, and psychological coping responses). In our study, different forms of social capital refer to bonding social capital originating from host national and co-national networks, bridging social capital, and maintained social capital. A web-based cross-sectional survey was conducted in January 2021. Our results demonstrated that the effects of social capital on psychological conditions differed according to its form. Worries about being infected, loneliness, and negative coping had negative associations with bonding social capital originating from host national network, but no associations with bonding social capital originating from co-national network, bridging social capital, and maintained social capital. Subjective wellbeing had a positive relationship with social capital originating from host national network and bridging social capital. Positive coping was only significantly associated with bridging social capital. To help international students cope better with the pandemic, efforts are required to strengthen their host national networks and expand their weak-tie networks.

The fact that COVID-19 caused unprecedented challenges for the first time in the human race and eventually rose against all odds in such a short period is a testament to transdisciplinary capacity building. This study analyzes the approaches to disaster management during the pandemic by examining some cases in the Asian region. Managing disasters during a pandemic requires a transdisciplinary approach (TDA), including multi-sectoral coordination, and an interdisciplinary approach based on sound knowledge sharing. The session, in September 2021, in which nine presenters participated, discussed the role of TDA in managing disasters. Through this special session, it was found that the TDA contributed to managing disasters in complex situations, and three characteristics could be identified. First, as per institutional arrangements, case studies show how disaster risk reduction agencies, which had been responding to the expected scale of disasters, have started to respond to multiple different disasters and infectious diseases because of COVID-19. Second, public trust based on sound knowledge and information sharing is essential for promoting multi-stakeholder coordination. Third, information and communication technology utilization was found not only for information sharing and contact-base registration systems on disaster response to COVID-19 but also for monitoring the reconstruction process after a disaster in a remote manner. Further analysis and review will be conducted to develop these evolving practices to build disaster resilience.

With the emergence of COVID-19, the disasters and risk factors that companies must deal with have become more diverse. This study categorizes these risks into three categories: traditional natural disasters, which have been occurring for a long time but have become more serious and frequent in recent years, the newly emerged COVID-19, and the changes in social values that COVID-19 has accelerated. We organized and compared the characteristics and risk factors of these three major categories of disasters, as well as the measures we are taking and should take. In the future, we plan to further investigate how each disaster and risk factor actually pose a risk to companies and to deepen our research on the roles of companies, supply chains, industries, governments, and the international community.