The monograph contains the results of studying the mechanisms of the development of coronavirus infection, changes in the blood, which has become one of the urgent scientific problems in recent years. The monograph is the result of many years of observations and research of the authors, in which the principles of clinical laboratory diagnosis of changes in endothelial dysfunction in coronavirus infection were formed. A detailed interpretation and analysis of the scientific works of other authors on this issue is also given. The book is dedicated to hematologists, infectious disease specialists, therapists, general practitioners and all medical specialties.