Spread of COVID-19 and Its Main Modes of Transmission

The coronaviruses group can affect mammals, including humans, causing generally mild infectious disorders, sporadically leading to severe outbreak clusters, such as those generated by SARS-CoV in 2003 and by MERS-CoV in 2012 and in 2015. The current coronavirus outbreak started December 29th, 2019 in Wuhan (Republic of China) and has progressively expanded to various parts of the world. A human-to-human transmission of COVID-19 occurs directly through individuals showing symptoms. But, recent researches support the possibility of SARS-CoV-2 transmission from persons who are asymptomatic. Indirect transmission occurs via touching infected surfaces or through inhalation of small, exhaled virus in respiratory droplets. To effectively fight the spread of COVID-19, it is vital to understand the different factors that promote superspreading of COVID-19. So, the aim of this chapter is to describe the invasion of SARS-CoV-2 in the human body and the different modes of transmission (directly and indirectly).