Global Epidemiology and Transmission of COVID- 19

Coronavirus Disease 2019 (COVID-19) is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It started as an outbreak in Wuhan, China, at the end of 2019. But within a few months, it took the form of a deadly pandemic affecting millions of people in more than 216 countries. Transmission via a large number of asymptomatic cases and international travel played a pivotal role in the spread of infection to different geographical regions. In the present chapter, we have given the chronological details about the spread of the infection across the globe. The countries with the greatest international connectivity showed a large number of cases. Further, the countries that suspended international travelling and sealed their borders are the ones that have managed the spread impressively. Subsequently, we have summarized the emergence of human Coronaviruses (SARS, SARS-CoV-2 and MERS) in humans. We have also described the different modes of human to human transmission of SARS-CoV-2. However, the infectivity is undercounted as many patients with mild or no symptoms are not getting tested. The present chapter summarizes the origin, global epidemiology and modes of transmission of the infection. Comprehensive hospital and community-based surveillance and detailed interpretation of full genomes of SARS-CoV-2 need to be carried out across different geographical regions. This data will assist in the demarcation of mutation rates and resultant evolutionary trajectory of this emerging viral pathogen. Preventive measures like social distancing, wearing masks and good hygiene should be followed religiously to prevent the spread of the contagion.

Keywords: COVID-19, Epidemiology, Origin, Pandemic, SARS-CoV-2, Transmission.