Original ResearchUsing daily syndrome-specific absence data for early detection of school outbreaks: a pilot study in rural China
Introduction
School children are at high risk of infection with communicable diseases, particularly acute respiratory virus infection, due to high population density, close contact and low immunity.1 This was demonstrated by the 2009 influenza H1N1 pandemic, which affected children more severely than adults in terms of attack rate and disease severity.2 Furthermore, children play an important role in the transmission of infectious diseases, particularly to their family members.3, 4 As such, it is necessary to control infectious diseases among children.
In China, approximately 70% of public health emergencies occur in schools, and approximately 60% occur in rural schools due to poor sanitation and lack of health knowledge.5, 6 When disease outbreaks or epidemics occur in schools, they jeopardize the physical and mental health of students, affect routine teaching activities, and can even have an adverse effect on the local society.7 As such, timely detection and reporting is very important in order to take prompt action and reduce the effect. Since 2004, cases of infectious disease and public health emergencies have been required to be reported to the Chinese Information System for Diseases Control and Prevention (CISDCP).8 In 2006, the Chinese Government issued a regulation to standardize and improve the detection and reporting of infectious disease cases or events in schools and nurseries.9 However, omissions and delays in reporting events are fairly common, especially in rural schools due to lower awareness.10, 11 A timely and effective early warning system for the detection of outbreaks in schools is needed urgently.
Surveillance of school absence has been used previously as part of syndromic surveillance for the early detection of disease outbreak,12, 13, 14 and was widely suggested as a proxy for the early detection of influenza activity in the community.15, 16, 17 Mook et al. found that the peak in school absence occurred earlier than that for the influenza laboratory data.17 However, most of these systems analysed data on a weekly basis, or using the overall rate of school absence. There is limited documentation of daily information or specific reasons for absence, which may be of great importance to improve the timeliness and sensitivity of surveillance.
Recognizing the importance of early outbreak detection in schools and the advantages of using absence data as an early indicator, a daily syndrome-specific absence surveillance system (DSSASS) was established in primary schools for the early detection of school outbreaks. This formed part of an ongoing research project on an integrated surveillance system funded by European Union Framework Program 7 (ISSC:241900).18 The pilot study was conducted in nine public elementary schools in rural areas of Hubei Province from 19 September 2011 to 31 December 2011. This article describes the establishment and initial operation of the system, reports the preliminary analysis and evaluation, and compares the surveillance data with data from CISDCP.
Section snippets
Study areas and surveillance sites
After consideration of the population characteristics, economic development, incidence of notifiable infectious diseases and willingness of the local health authorities, Qianjiang City and Shayang County in Hubei Province were selected as the study areas. Public elementary schools at different levels (i.e. county, township and village) were sampled under surveillance. Two county schools, two township schools and five village schools were selected for the pilot study, all of which comprised
Descriptive epidemiology
The total number of students in county, township and village schools among the nine participating schools was 5032, 1957 and 978, respectively. Table 1 shows the general characteristics of the absentees. The daily absence rate for all causes was 3.00%, which differed by area (χ2 = 1551.83, P = 0.00) and by school level (χ2 = 619.52, P = 0.00). The daily absence rate for all causes was highest in Shayang (5.99%) and in county schools (4.36%). Gender was not found to be significantly associated
Discussion
This epidemiological analysis provides a basic description of school absence resulting in better understanding of the surveillance system. The daily absence rate was higher in Shayang County and highest in county schools, which may reflect the occurrence of two outbreaks (varicella and influenza B) at Shayang County School and greater willingness and awareness of the reporters. The finding that absence rates were higher in lower grades was expected, as younger students are more susceptible to
Author statements
The authors wish to thank the schools that participated in this pilot study. In addition, the authors would like to thank Qianjiang and Shayang Centers for Disease Control and Prevention for coordinating with schools and for fieldwork. Finally, the authors wish to thank Lv Xin, Xue Li and Kenneth Engstrom for system development.
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