Management and operation of extra-large Fangcang hospitals: experience and lessons from containing the highly contagious SARS-CoV-2 Omicron in Shanghai, China

Introduction Omicron is more contagious and stealthier than the previous strains.The basic reproduction number of Omicron is around 8-12,whereas that of the previous mainstream strain Delta is only 5-8[1].Omicron's symptoms are relatively mild[2]compared with Delta's symptoms;however,Omicron's transmission ability is very strong,and its risk to children and the elderly remains high[3].In addition,the vaccine's preventive effect on Omicron has weakened.Therefore,Omicron can easily cause a rapid outbreak in a city.The population density of megacities and the limited public health resources fuirther exacerbate the difficulty of Omicron prevention and control.