the concept of the study of the stages of contagiousness of viruses and bacteria. red and green background with graph

2019 background bacteria blurred care colorful concept conceptual contagion contagious contagiousness corona coronavirus covid covid19 dangerous dark design disease epidemic epidemiology formulas graph graphic green hazard health infect infectious infectivity lethal medical microbiology ncov outbreak pandemic pathogenic pneumonia political red research scattered screen splash stages study viral virology virus viruses