General Center for Disease Control and Prevention of Inner Mongolia autonomous Region Huhehaot, Inner Mongolia Medical University, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, Inner Mongolia University, General Center for Disease Control and Prevention of Inner Mongolia autonomous Region Huhehaot, General Center for Disease Control and Prevention of Inner Mongolia autonomous Region Huhehaot and affiliation not provided to SSRN