Absenteeism in schools during the 2009 influenza A(H1N1) pandemic: a useful tool for early detection of influenza activity in the community?

Certain influenza outbreaks, including the 2009 influenza A(H1N1) pandemic, can predominantly affect school-age children. Therefore the use of school absenteeism data has been considered as a potential tool for providing early warning of increasing influenza activity in the community. This study retrospectively evaluates the usefulness of these data by comparing them with existing syndromic surveillance systems and laboratory data. Weekly mean percentages of absenteeism in 373 state schools (children aged 4-18 years) in Birmingham, UK, from September 2006 to September 2009, were compared with established syndromic surveillance systems including a telephone health helpline, a general practitioner sentinel network and laboratory data for influenza. Correlation coefficients were used to examine the relationship between each syndromic system. In June 2009, school absenteeism generally peaked concomitantly with the existing influenza surveillance systems in England. Weekly school absenteeism surveillance would not have detected pandemic influenza A(H1N1) earlier but daily absenteeism data and the development of baselines could improve the timeliness of the system.     

Strategy to Enhance Influenza Surveillance Worldwide

The emergence of a novel strain of influenza virus A (H1N1) in April 2009 focused attention on influenza surveillance capabilities worldwide. In consultations before the 2009 outbreak of influenza subtype H1N1, the World Health Organization had concluded that the world was unprepared to respond to an influenza pandemic, due in part to inadequate global surveillance and response capacity. We describe a sentinel surveillance system that could enhance the quality of influenza epidemiologic and laboratory data and strengthen a country’s capacity for seasonal, novel, and pandemic influenza detection and prevention. Such a system would 1) provide data for a better understanding of the epidemiology and extent of seasonal influenza, 2) provide a platform for the study of other acute febrile respiratory illnesses, 3) provide virus isolates for the development of vaccines, 4) inform local pandemic planning and vaccine policy, 5) monitor influenza epidemics and pandemics, and 6) provide infrastructure for an early warning system for outbreaks of new virus subtypes.     

无锡市发热呼吸道症状监测在甲型H1N1流感大流行中的早期预警效果分析

目的利用已有的非典预警及流感样病例两个症状监测系统,建立无锡市流感监测预警基线值,评价其在2009年甲型H1N1流感大流行中的早期预警效果。方法对2007～2009年无锡市非典预警数据及流感样病例监测数据进行分析,对2009年的流感样病例监测数据进行拟合,分析两个系统和不同方法对甲型H1N1流感大流行早期预警的效果。结果流感样病例监测数据(ILI%)自出现首例输入性病例前1个月就出现上升趋势;非典预警监测系统中发热呼吸道病例门诊就诊率高于2007、2008年同期水平(P﹤0.001),在出现本地病例前1周就出现上升趋势。控制图法显示,2009年流感疫情与2009年甲型H1N1流感不同阶段流行趋势基本一致。结论两个监测系统2009年预警信号和实际甲型H1N1流感疫情基本吻合;移动平均回归法预警甲型H1N1流感暴发较控制图法在流行时间上更为精准。     

The effect of school dismissal on rates of influenza-like illness in New York City schools during the spring 2009 novel H1N1 outbreak

BACKGROUND: The effects of individual school dismissal on influenza transmission have not been well studied. During the spring 2009 novel H1N1 outbreak, New York City implemented an individual school dismissal policy intended to limit influenza transmission at schools with high rates of influenza‐like illness (ILI). METHODS: Active disease surveillance data collected by the New York City Health Department on rates of ILI in schools were used to evaluate the impact. Sixty‐four schools that met the Health Department's criteria for considering dismissal were included in the analysis. Twenty‐four schools that met criteria subsequently dismissed all classes for approximately 1 school week. A regression model was fit to these data, estimating the effect of school dismissal on rates of in‐school ILI following reconvening, adjusting for potential confounders. RESULTS: The model estimated that, on average, school dismissal reduced the rate of ILI by 7.1% over the entire average outbreak period. However, a large proportion of in‐school ILI occurred before dismissal criteria were met. A separate model estimated that school absenteeism rates were not significantly affected by dismissal. CONCLUSION: Results suggest that individual school dismissal could be considered in situations where schools have a disproportionate number of high‐risk students or may be unable to implement recommended preventive or infection control measures. Future work should focus on developing more sensitive indicators of early outbreak detection in schools and evaluating the impact of school dismissal on community transmission.     

沈阳市流行性感冒监测数据的早期预警效果

目的利用现有的流行性感冒(流感)监测数据,探讨流感早期预警指标及其在2009年甲型流感大流行中的预警效果。方法选用沈阳18所哨点医院门诊流感样病例既往监测数据,采用控制图法,建立预警线,对2009和2010年的流感样病例百分比(ILI%)数据进行拟合,并结合新甲型H1N1疫情和病原学监测结果综合分析其早期预警效果。结果控制图法显示,ILI%较病原学监测和大疫情数据提前1周超过警戒线,ILI%趋势于新甲型H1N1疫情、流感病毒检出率变化趋势基本一致。结论 ILI%作为流感活动的监测指标较为可靠,控制图法可作为流感大流行敏感有效的早期预警指标。     

Direct and indirect impact of influenza vaccination of young children on school absenteeism

Special mass influenza vaccination programs of elementary school-aged children (ESAC) in some or all Maryland Counties were conducted during the falls of 2005-2007. From 3% to 46% of ESAC received live attenuated influenza vaccine during these county programs, which were in addition to routine influenza vaccination efforts conducted in county medical offices. Anonymous, all cause public school absentee data for all grades was available from 11 of Maryland's 24 counties. Binomial regression was used to estimate associations between the percentage of children vaccinated in each county and the degree of increase in absenteeism rates during influenza outbreaks. We estimated that, for every 20% increase in vaccination rates for ESAC during these special programs, a 4% decrease in the rise in absentee rates occurred during influenza outbreak periods in both elementary and upper schools (P < 0.05). These results suggest both direct and indirect benefits of influenza vaccination of young children.     

Effects of hand hygiene campaigns on incidence of laboratory-confirmed influenza and absenteeism in schoolchildren, Cairo, Egypt

To evaluate the effectiveness of an intensive hand hygiene campaign on reducing absenteeism caused by influenza-like illness (ILI), diarrhea, conjunctivitis, and laboratory-confirmed influenza, we conducted a randomized control trial in 60 elementary schools in Cairo, Egypt. Children in the intervention schools were required to wash hands twice each day, and health messages were provided through entertainment activities. Data were collected on student absenteeism and reasons for illness. School nurses collected nasal swabs from students with ILI, which were tested by using a qualitative diagnostic test for influenza A and B. Compared with results for the control group, in the intervention group, overall absences caused by ILI, diarrhea, conjunctivitis, and laboratory-confirmed influenza were reduced by 40%, 30%, 67%, and 50%, respectively (p<0.0001 for each illness). An intensive hand hygiene campaign was effective in reducing absenteeism caused by these illnesses.     

Comparison of the pandemic H1N1 2009 experience in the Southern Hemisphere with pandemic expectations

Objective: To describe the epidemiological characteristics of the 2009 H1N1 pandemic virus (pH1N1) over the 2009 and 2010 influenza seasons in Australia and New Zealand (NZ) and compare them with expectations based on previous pandemics. Methods: Laboratory‐confirmed influenza and influenza‐like illness (ILI) data were collected from established general practitioner sentinel surveillance schemes in NZ, Victoria and Western Australia (WA) throughout the 2009 and 2010 winter influenza seasons. Respiratory swabs from a sample of ILI patients were tested for influenza type and subtype. ILI rates and laboratory‐confirmed influenza data were analysed by age group and over time. Morbidity, mortality and reproductive number data were collated from the published literature. Results: Peak ILI rates and the percentage of influenza‐positive swabs from ILI patients from all sentinel surveillance schemes were considerably lower in 2010 than 2009. Compared to the population, cases of ILI were over‐represented in the young. While the age distributions in NZ and WA remained consistent, ILI cases were significantly younger in Victoria in 2009 compared to 2010. In Victoria, laboratory‐confirmed pH1N1 comprised up to 97% of influenza‐positive swabs in 2009 but only 56–87% in 2010. Mortality and hospitalisations were lower in 2010. The effective reproduction number (R) for pH1N1 was estimated to be 1.2–1.5 in NZ and WA, similar to estimated R values for seasonal influenza. Data from the surveillance systems indicated differences in the epidemiology of pH1N1 compared to expectations based on previous pandemics. In particular, there was no evidence of a second pandemic wave associated with increased mortality, and complete influenza strain replacement did not occur. Implications: Pandemic planning needs to accommodate the potential for influenza viruses to produce pandemics of various infectiousness and degrees of severity.     

Demographic Shift of Influenza A(H1N1)pdm09 during and after Pandemic, Rural India

Population-based active surveillance in India showed higher incidence rates for influenza A(H1N1)pdm09 among children during pandemic versus postpandemic periods (345 vs. 199/1,000 person-years), whereas adults had higher rates during postpandemic versus pandemic periods (131 vs. 69/1,000 person-years). Demographic shifts as pandemics evolve should be considered in public health response planning.     

流感监测预警曲线的测定及应用

[目的]利用已有的流感监测数据制定福田区流感监测基线和预警曲线,进行早期预测。[方法]采用2005～2009年两所医院的流感样病例百分比监测数据(ILI%),通过统计分析制定基线和预警曲线。[结果]福田区流感基线值为4.10%,预警值为7.95%,警戒曲线反映的异常波动与2010年实际的暴发疫情及病原分离结果相一致。[结论]福田区的流感监测预警曲线具有较好的灵敏性和准确性,能对流感疫情进行早期预警。     

天河口岸甲型H1N1流感的检疫查验情况分析

目的分析天河口岸甲型H1N1流感的检疫查验情况,为出入境口岸传染病监测和预防控制工作提供科学依据。方法对2009年5月1日至8月10日经天河口岸出入境并被施以流行病学调查、采样等措施的旅客,收集其国籍、出入境日期、性别、年龄、体温、症状、旅行史、诊断结果等信息,并对资料进行分析。结果受检人群共823人;共检出甲型H1N1流感阳性病例31人;不同月份或体温分组人群的H1N1检出率不同,受检人群的H1N1检出率逐月升高;性别、旅行史或咳嗽等伴随症状受检人群的检出率无统计学意义。结论当前甲型H1N1流感越来越严重,正处于高发时期,广州已呈现疫情社区流行的特征。应适当调整总体检疫策略,从以防止疫情传入、阻击输入性病例为重心的策略,过渡到以监测、预防、遏制疫病社区暴发为重心的策略上来。另外,建议加强体温监测,以确保更加全面的检测甲型H1N1流感。     

The 2005 Wellington influenza outbreak: syndromic surveillance of Wellington Hospital Emergency Department activity may have provided early warning

Objectives: To assess whether the Wellington Emergency Department (ED) Respiratory Syndromic Surveillance System may have provided early warning of the influenza outbreak in Wellington schools during 2005, and as a result might have provided the opportunity for an earlier or more effective public health response.
Methods: All events of respiratory syndrome, as defined by selected ICD 10 codes, were extracted from Wellington Hospital ED for the dates 1 January 2004 to 31 December 2006, and analysed using the Centers for Disease Control and Prevention (CDC) surveillance program, Early Aberration Reporting System (EARS). Daily events were analysed for total counts and by lifecycle age group. Seven day moving averages of the numbers of events were also calculated.
Results: This study indicated that the surveillance system may have provided early warning of a potential respiratory outbreak. Regular exceedance flags were generated nine days prior to the initial notification received by Regional Public Health (RPH). The surveillance system also provided information on the type of illness (respiratory), the groups affected (5-14 year olds), and the progression of the outbreak (peak, end).
Conclusions: The surveillance system might have worked by providing early notification of the outbreak. This may have prompted RPH to earlier investigate the potential outbreak and may have led to an earlier response.
Implications: Surveillance of Emergency Department activity may be useful for early public health response.     

中国流感监测网络的发展与展望

流感引起的每年季节性流行在全球造成严重的疾病负担,而且流感还会不定期引起世界性流感大流行,造成严重社会恐慌、经济损失。由于流感病毒的高度可变性和不可确定性,流感防控面临诸多挑战。监测是预防和控制流感的关键策略,流感也是第一个实行全球监测的传染病。中国流感监测60余年,为我国和全球流感防控做出了巨大贡献。特别是近10余年来,流感监测网络得以飞跃发展,规模显著扩大,监测内容和范围不断完善,监测质量迅速提升。中国流感监测网络是我国和全球新发传染病病原的早期发现体系之一,为新发突发传染病应对准备了技术和人才队伍,有助于全面提升公共卫生系统对新发传染病的防控和预测预警能力。     

A Bayesian dynamic model for influenza surveillance

The severe acute respiratory syndrome (SARS) epidemic, the growing fear of an influenza pandemic and the recent shortage of flu vaccine highlight the need for surveillance systems able to provide early, quantitative predictions of epidemic events. We use dynamic Bayesian networks to discover the interplay among four data sources that are monitored for influenza surveillance. By integrating these different data sources into a dynamic model, we identify in children and infants presenting to the pediatric emergency department with respiratory syndromes an early indicator of impending influenza morbidity and mortality. Our findings show the importance of modelling the complex dynamics of data collected for influenza surveillance, and suggest that dynamic Bayesian networks could be suitable modelling tools for developing epidemic surveillance systems.     

Medication sales and syndromic surveillance, France

Although syndromic surveillance systems using nonclinical data have been implemented in the United States, the approach has yet to be tested in France. We present the results of the first model based on drug sales that detects the onset of influenza season and forecasts its trend. Using weekly lagged sales of a selected set of medications, we forecast influenzalike illness (ILI) incidence at the national and regional level for 3 epidemic seasons (2000-01, 2001-02, and 2002-03) and validate the model with real-time updating on the fourth (2003-04). For national forecasts 1-3 weeks ahead, the correlation between observed ILI incidence and forecast was 0.85-0.96, an improvement over the current surveillance method in France. Our findings indicate that drug sales are a useful additional tool to syndromic surveillance, a complementary and independent source of information, and a potential improvement for early warning systems for both epidemic and pandemic planning.     

中国人感染H7N9禽流感危险区域预警识别的研究

目的 建立人感染H7N9禽流感发病危险预警模型, 识别禽流感暴发高危险区域并提出预警。方法 收集2013年2月至2014年6月中国地市级人感染H7N9禽流感病例数据及同期地理、气象数据, 通过空间自回归(SAR)模型和广义相加模型(GAM)拟合并量化地理和气象因素对发病的影响, 综合两模型的预测结果建立发病危险预警地图。结果 2014年2月中国人感染H7N9禽流感的实际发病地区全部位于研究构建的发病危险预测区域内;模型预测了疾病的空间移动趋势, 对2014年4、5月北方地区的新发疫情有准确的预警。结论 建立的模型短期预测准确度和精确度较好, 可应用于疫情监测和预警领域, 有助于早期区域预防疫情的流行及暴发。     

珠海市2006-2008年流感症状监测分析及预测

目的 了解广东省珠海市2006-2008年流感流行趋势及其病毒株变化特点,预测2009年流行趋势,为本地区防控流感提供科学依据.方法 收集2006-2008年珠海市流感监测哨点流感样病例(ILl)监测和暴发疫情监测资料信息,医院门诊、暴发疫情的流感病毒病原学监测资料,进行综合分析.采用季节性自回归移动平均(ARIMA)构建模型预测2009年ILI的趋势.结果 2006-2008年珠海市流感流行大致呈3-4月和6-7月的双峰型,平均ILI%为4.1%;门诊报告ILI中<5岁儿童为主,占50.3%,构成比逐年上升.哨点医院流感病毒分离阳性率为10.0%,2006年流感季节类型为A(H1N1)型和B型混合型,2007年为A(H3N2)型占优势,2008年为A(H1N1)型和A(H3N2)型混合型.暴发疫情主要发生在3-6月,流行病毒株与医院哨点监测基本一致.结论 珠海市流感流行呈现春夏季双峰型,ILI的高峰较流感病毒早4周左右;H3型、H1型、B型流感病毒交替成为年分离优势株.预测2009年季节性流感流行趋势平稳.     

2009—2010年青海省新甲型H1N1流感流行特征分析

目的分析2009—2010年新甲型H1N1流感在青海省的流行情况。方法收集"中国流感监测信息系统"中青海省报告的甲型H1N1流感病原学监测数据和全国第6次人口普查人口数据资料,采用Excel 2003软件建立数据库进行统计分析。结果全省确诊甲型H1N1流感2 034例,发病高峰在2009年9—10月。西宁市标化发病率为78.48例/10万,为全省各地最高。男性甲型H1N1流感发病率高于女性,差异有统计学意义(χ2=1 190.9150,P<0.0001)。在控制了性别因素的影响后,甲型H1N1流感发病率随年龄增加而降低,差异有统计学意义(χ2=36.5890,P<0.0001)。结论青海省甲型H1N1流感发病高峰在2009年9月份出现,较往年普通季节性流感提前,病例主要集中在西宁地区,发病率男性较女性高并随年龄增加而降低。     

Measuring the impact of influenza vaccination on healthcare worker absenteeism in the context of a province-wide mandatory vaccinate-or-mask policy

ObjectivesIn 2012, British Columbia (BC) implemented a province-wide vaccinate-or-mask influenza prevention policy for healthcare workers (HCWs) with the aim of improving HCW coverage, and reducing illness in patients and staff. We assess post-policy impacts of HCW vaccination status on their absenteeism.MethodsWe matched individual HCW payroll data from December 1, 2012 to March 31, 2017 with annually self-reported vaccination status for BC health authority employees to assess sick rates (sick time as a proportion of sick time and productive time). We modelled adjusted odds ratios (OR) of taking any sick time, relative rates (RR) of sick time taken, and predicted mean sick rates by vaccination status in influenza (December 1–March 31) and non-influenza seasons (April 1 to November 30). We used two methods to assess changes in influenza season sick rates for HCWs who had a change in their vaccination status over the five years.ResultsHCWs who reported ‘early’ vaccination (before December 1 when the policy is in effect) were less likely to take sick time (OR 0.874, 95%CI: 0.866–0.881) and took less sick time (RR 0.907, 95%CI: 0.901–0.912) in influenza season compared to HCWs who did not report vaccination; whereas HCWs who reported ‘late’ (between December 1 and March 31, and subject to masking until vaccinated) had similar sick rates to HCWs who did not report vaccination. These trends were also observed in non-influenza season. Influenza season sick rates were similar for HCWs that had at least one year of ‘early’ vaccination and one year where vaccination was not reported over the five year period.ConclusionsOverall absenteeism is lower among HCWs who report vaccination versus those who do not report. However, absenteeism behaviours appear to be influenced by individual level factors other than vaccination status.