In December 2019, an unknown pneumonia rapidly spread in Wuhan, China, a new coronavirus, 2019 novel coronavirus (2019-nCoV), aroused the attention of the entire world. On January 31, 2020, World Health Organization (WHO) announced the outbreak of Coronavirus Disease 2019 (COVID-19) in China as a Public Health Emergency of International Concern. The number of volunteer non-remunerated blood donors decreased because of quarantine, caring for relatives, and fear of exposure to COVID-19. Due to the blood shortage, patient blood management and cessation of elective surgery are contributing to decreased demand, but sepsis may increase requirements and significant reductions will not be possible in areas such as trauma, cancer patients, hereditary haemolytic anaemias and childbirth. Therefore, recruiting enough blood donors during the epidemic is vital for public health in China, and also worldwide. In order to assess the effects of a questionnaire on blood donor recruitment, the investigators designed two kinds of self-administered, standardized and structured questionnaires. In addition of the basic socio-demographic characteristics, one questionnaire includes the information of precautions of blood donation during epidemic, and the other dose not. The questionnaires were randomly sent to ever blood donors, and the same number of ever blood donors are coded as control.

In order to assess the effects of a questionnaire on blood donor recruitment, the investigators designed two kinds of self-administered, standardized and structured questionnaires. In addition of the basic socio-demographic characteristics, one questionnaire includes the information of precautions of blood donation during epidemic, and the other dose not.

Information of precautions of blood donation during epidemic included taking donor's temperature and enhancing hand disinfection before donation etc.

The questionnaires were randomly sent to ever blood donors, and at the same day, equal number of ever blood donors as the ones who filled the questionnaire are coded as control.

Inclusion Criteria:

• Blood donors whose last donation were between 1 Feb to 31 March, 2019.

Exclusion Criteria:

• Blood donors whose blood test results were positive. Blood donors who were aged above 60. Blood donors whose cell phone number was obviously invalid.