Epidemics and pandemics of infectious disease

ABSTRACT

Throughout the course of civilization, epidemics and pandemics have ravaged humanity, destroyed animal breeding and horticulture, and has also changed the course of history. It has been estimated that Justinian plague has affected half of the population of Europe and killed in three pandemics 50 million people, the avian-borne flu (Spanish flu), resulted in 50 million deaths worldwide in the years 1918-1919, and recently the COVID-19 is officially a pandemic, after barreling through 114 countries in just three months. In the past, rinderpest has hit Europe with three long panzootics, African swine fever (ASF), is still a threat to both the swine production industry and the health of wild boar populations. Several molecular changes occur in the pathogen that may trigger an epidemic or even pandemic. These include increase of virulence, introduction into a novel host, and changes in host susceptibility to the pathogen. Once the infectious disease threat reaches an epidemic or pandemic level, the goal of the response is to mitigate its impact and reduce its incidence, morbidity and mortality as well as disruptions to economic, political, and social systems. An epidemic curve shows progression of illnesses in an outbreak over time and the SIR, SI, SIRD and SEIR represent the simplest compartmental models that enable simplify the mathematical modelling of epidemics. This article throws a light on changing ideas in epidemiology of infectious diseases.