摘要
The coronavirus disease 2019(COVID-19)pandemic is the biggest pandemic of its kind in modern times,and has been running for over two years.It has grown exponentially from a cluster of unexplained cases of pneumonia in December 2019 to a full-grown pandemic[1].With a sharp ascending limb in its initial stages,it was announced by the World Health Organization as public health emergency of international concern on January 30,2020,subsequently acquiring the definition of a pandemic on March 11,2020.
