摘要
Coronavirus disease(COVID-19)is an infectious disease caused by a novel severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).The first reported outbreak of COVID-19 was in China in December 2019.The World Health Organization(WHO)declared the outbreak a Public Health Emergency of International concern in January 2020 and a pandemic in March 2020.Italy confirmed its first cases in January 2020,and Nigeria in February 2020.By July 2020,more than 15.3 million COVID-19 cases were reported in more than 188 countries,resulting in over 630,000 deaths;although more than 9.3 million people recovered.
