Survey of influenza B outbreak in a middle school in Kashigar Osmanjian

Objective To analyze the characteristics of an influenza like illness(ILI)outbreak occurred in No.6 middle school in Kashigar from 18 March to 2 April,2009, identify the outbreak cause and discuss the prevention and control measures. Methods Field epidemiological survey and descriptive epidemiological analysis were conducted. Two throat swabs were detected by rapid influenza diagnostic tests of type A+B. Results A total of 155 ILI cases occurred,2 of which were influenza B virus positive by the rapid diagnostic tests. The average attack rate was 4.18%(155/3710), which was 6.07% in boys(98/1614), and 2.72%(57/2096)in girls. The first case occurred on 18 March,and the incidence peaked on 21 and 22 March. All the cases were the students living in school, and most of them were the students in higher grade(99.36%). The incidence in boys was higher than in girls. Conclusion It is important to report the outbreak of infectious diseases in school timely and give early warning. The immunization should be conducted when it is necessary to control the outbreak.