Preface

The pandemic of COVID-19, caused by the SARS-CoV-2 virus (Severe Acute Respiratory Syndrome Coronavirus 2), has shaken up our societies, with an intensity and effects not suffered by humanity for a long time. To date, there have been registered millions of deaths associated to COVID-19, and hundreds of millions of confirmed cases all around the world. Moreover, this pandemic has triggered not only a deep and global health crisis, but also an economic and social (without mentioning psychological, educational, etc.) crisis like never seen before.

In order to endure and overcome this major tribulation, the different human communities, guided by their respective administrations and governments, have been put to the test in multiple and severe ways, under the direct effects of the disease, and the performance of several therapeutical and non-pharmaceutical interventions and mitigation measures. Among others, we could mention: the severity of symptoms and disease evolution in serious and critical cases (including assisted ventilation), and the long-term effects; the lack of effective treatments, specially in the first stages; unstoppable death tolls and incidence rates, with increasing numbers of hospitalizations that press and even saturate the health care national systems; hygiene or sanitary measures (frequent hand washing, not touching the face, the generalized use of disinfection products, the use of masks, gloves, and glasses, etc.); the use of detection tests (as PCR); quarantines, home isolation and confinements; the implementation of severe social distancing and isolation measures (indeed curfews in some cases); mobility, travel, circulation and gathering restrictions, and closure of borders; reduction or suspension of nonessential activities, with loss of millions of jobs and increasing unemployment rates; total or partial closure of colleges and universities and the unequal and frequently improvised performance of on-line education; campaigns for tracing possible cases; vaccination programs; the psychological effects on mental health in the community; etc.

Hence, this picture entailed the scientific community to face to an unprecedented challenge, in order to appropriately assess and advise health authorities and decision-makers. Such a kind of complex phenomena appeals to multidisciplinary and interdisciplinary groups of experts to take their part in order to reach a comprehensive approach, able to deal with the many relevant and multifactorial aspects of COVID-19, as illness and as pandemic. Of course, topics as the epidemiological and clinical aspects of the disease are central, but not the unique ones. Other matters require to be understood, as the SARS-CoV-2 virology, or the COVID-19 pathophysiology and immunology; the study of temporal evolution of infected individuals and their contagiousness; the lack of preparedness of the health care systems and the rapid reaction in Medicine research, including the development and access to vaccines; the population heterogeneity and the effects of mobility and human behavior in the spread of the disease; the role of health and social inequities; etc.

In this context, the appearance of scientific works, which organize and summarize a great part of the scientific job carried out, is of great value. In particular, if the subject is approached from a comprehensive and multidisciplinary perspective, considering the individual and collective levels, and their temporal and spatial evolution, the biological, socioeconomic, technological aspects, etc., and its consequences for the societies in which it occurs, as the current work does. In addition, the case of this scientific work is especially interesting, since it highlights the role that Mathematical and Computational Modeling can play together with other related areas such as Data Science and Statistics, when dealing with this type of multidisciplinary phenomenon, for which is an excellent reference for researchers and decision makers on how to deal with this type of problem.

Based on all that has been said above, I hope that this book will help researchers and decision makers to better understand and evaluate the situations that can arise in the context of a complex problem such as that caused by the COVID-19 pandemic and the way to face it.