1 Chief of Service, Department of Family Medicine and Primary Care, HKU-Shenzhen Hospital, China; Department of Family Medicine and Primary Care, The University of Hong Kong, 3/F, Ap Lei Chau Clinic, 161 Ap Lei Chau Main Street, Ap Lei Chau, Hong Kong, China. Electronic address: wongwcw@hku.hk.
3 Community Health Centre of Fengyuan Street, Liwan Guangzhou, No.167-1 Fengyuan Road, Liwan, Guangzhou, China. Electronic address: 1397342776@qq.com.
4 Department of Family Medicine and Primary Care, The University of Hong Kong, 3/F, Ap Lei Chau Clinic, 161 Ap Lei Chau Main Street, Ap Lei Chau, Hong Kong, China. Electronic address: kccwy@hku.hk.
5 Department of Sexually Transmitted Diseases, Dermatology Hospital, Southern Medical University, Guangzhou, 510091, China. Electronic address: yanglg3@hotmail.com.