Epidemiology of the COVID-19 Pandemic: An Update

Due to the emergence of a large, deadly pandemic of COVID-19, it is important to document the worldwide impact of the pandemic in terms of morbidity and mortality. This chapter discusses the infectiousness, pathogenicity, and virulence of SARS-CoV-2, the virus causing COVID-19. This chapter provides a comparative analysis of the prevailing variants, such as delta and omicron. Epidemiologic information also includes risk factors, the impact of the pandemic on mental health, and complications, including long-COVID symptoms. The chapter provides special attention to the assessment of the disease burden in a country by using a recently revised formula of PYLL. Because of the weaning of protection from the previous monovalent vaccines and the introduction of bivalent vaccines, the chapter discusses the current data on vaccine effectiveness.