Epidemiology of COVID-19

COVID-19, an infectious respiratory illness caused by the severe acute respiratory syndrome–corona virus 2 (SARS-CoV2), has now spread to multiple countries including India. The pace at which the disease spread in the last 4 months, since it was first recognized from China, is unprecedented. This review of the epidemiology of COVID-19 summarizes the burden of infection, transmission dynamics, and other related epidemiological features. While countries such as China, Italy, and the United States have particularly high-rates of infection, the disease is gradually spreading in India as well, threatening the health and economy of the country. Transmission in asymptomatic cases, early symptomatic phase, as well as limited access to testing in different settings are factors that have led to the rapid spread of infection. A large case series from China revealed that 81% of cases had mild symptoms, 14% had severe disease, and 5% were afflicted with critical illness. While the mortality in China was reported as 2.3%, Italy, with a high-proportion of elderly, reported a case fatality report of 7.2% due to higher infection and mortality rates among the elderly. Being a highly infectious disease, with a basic reproduction number between 2 to 3, COVID-19 is affecting a large number of healthcare workers, as evidenced by the fact that a sizeable portion of reported infections in the US included healthcare workers. Delivering health care for both COVID-19 affected individuals, as well those with other acute and chronic conditions, with limited access to healthcare facilities and services, are challenges for the health systems in low- and middle-income countries, which require immediate measures for health system strengthening across sectors.