Crisis is an emergent event that threatens the national security, social regulation, civilian property and life, and needs urgent, decisive response in the condition of high instability. Crisis management should be prompt, active, honest, responsible and soluble, and should be carried out according to the model of preparation, reduction, response and recovery. SARS outbreak in China revealed constitutive defects in the immediate response for emergent public health event as well as crisis management. This paper provides some information for establishing the immediate response system for emergent public health event and crisis management.

Objective:To strengthen the research on theory and method of early warning for emergent public health event,so as to obtain timely information,correctly analyze the situation,and apply effective measures when the event happens.Methods: The definition of vulnerability of emergent public health event and the vulnerability factors were discussed.The indicator system and the evaluating method for public health vulnerability were systematically studied.The extenics theory and the theory of vulnerability evaluation were used for warning exercise.Results: We constructed an extenics model for early warning of emergent public health event;the model was used to evaluate the public health of a population.Conclusion: The theory of vulnerability evaluation is introduced in emergent public health event to construct an extenics model for early warning of emergent public health event;the model can be used to evaluate the public health of certain population.

BACKGROUND: The normal clinical index and the standard error of ultrasonic bone density in the population of normalchildren aged 6-12 years have not yet been established. OBJECTIVE: To investigate the status of ultrasonic bone density in the population of normal children aged 6 to 12 years old in Shenzhen City and establish a normal reference index of ultrasonic bone density of this population. DESIGN: Cross-sectional survey. SETTING: Ultrasound Department of People's Hospital in Longgang District of Shenzhen City. PARTICIPANTS: The volunteers for ultrasonic bone density detection were chosen froma kindergarten, an elementary school and a middle school between March 2002 and April2003. Excluded were those who had bone fracture and received medication of hormone and other drugs within 6months that affected bone metabolism, and menstrual history. Altogether we chose 697 normal children, 367 boys and 330 girls whose age ranged from 6 to 12 years old. METHODS: SAHARA ultrasonic bone density apparatus (the US) was used, and corrected according to the standard body model after the operation began.The error of precision was below 1％ and the error of accuracy was 3％. Bone density of the left heel of the children was detected and body mass (kg) and height (cm) were also measured using the same height and weight scale. MAIN OUTCOME MEASURES: The correlation between bone densityof the heel and sex, age and body mass in the population of normal children aged 6 to 12 years. RESULTS: The normal reference values of bone density in the population from 6 to 12 years old were (0.445±0.166) g/cm2 in 6-year-old group,(0.509±0.151) g/cm2 in 7-year-old group, (0.510±0.133) g/cm2 in 8-year-old group, (0.519±0.132) g/cm2 in 9-year-old group, (0.520±0.153) g/cm2 in 10-year-old group, (0.53±0.175) g/cm2 in 11-year-old, and (0.545±0.206) g/cm2 in 12-year-old group. There were differences in bone density between boys and girls (P ＜ 0.001), and after correction by body mass, the difference disappeared. Bone density of the boys and girls had increasing linear correlation with age (male r=0.722, P ＜ 0.001; female r=0.785, P ＜ 0.001), and had significant relationship with body mass (r=0.984, P ＜ 0.001). CONCLUSION: In normal children aged 6 to 12 years old, bone density of the heel has no association with sex, but has increasing linear correlation with age and significant relationship with body mass.