Applying symptom dynamics to accurately predict influenza virus infection: An international multicenter influenza‐like illness surveillance study

BackgroundPublic health organizations have recommended various definitions of influenza‐like illnesses under the assumption that the symptoms do not change during influenza virus infection. To explore the relationship between symptoms and influenza over time, we analyzed a dataset from an international multicenter prospective emergency department (ED)‐based influenza‐like illness cohort study.MethodsWe recruited patients in the US and Taiwan between 2015 and 2020 with: (1) flu‐like symptoms (fever and cough, headache, or sore throat), (2) absence of any of the respiratory infection symptoms, or (3) positive laboratory test results for influenza from the current ED visit. We evaluated the association between the symptoms and influenza virus infection on different days of illness. The association was evaluated among different subgroups, including different study countries, influenza subtypes, and only patients with influenza.ResultsAmong the 2471 recruited patients, 45.7% tested positive for influenza virus. Cough was the most predictive symptom throughout the week (odds ratios [OR]: 7.08–11.15). In general, all symptoms were more predictive during the first 2 days (OR: 1.55–10.28). Upper respiratory symptoms, such as sore throat and productive cough, and general symptoms, such as body ache and fatigue, were more predictive in the first half of the week (OR: 1.51–3.25). Lower respiratory symptoms, such as shortness of breath and wheezing, were more predictive in the second half of the week (OR: 1.52–2.52). Similar trends were observed for most symptoms in the different subgroups.ConclusionsThe time course is an important factor to be considered when evaluating the symptoms of influenza virus infection.     

Hospital‐based influenza morbidity and mortality surveillance system for influenza‐like illnesses: a comparison with national influenza surveillance systems

The Hospital‐based Influenza Morbidity and Mortality (HIMM) surveillance system is an emergency room (ER)‐based influenza surveillance system in Korea that was established in 2011. The system was established under the assumption that integrated clinical and virologic surveillance could be performed rapidly and easily at seven tertiary hospitals' ER. Here, we assessed the correlation between data generated from the HIMM surveillance system and the Korean national influenza surveillance systems during the 2011–2012 influenza season using cross‐correlation analysis and found strong correlations. Rapid antigen‐test‐based HIMM surveillance would predict the start of influenza epidemic earlier than pre‐existing influenza‐like‐illness‐based surveillance.     

Influenza surveillance in Europe: comparing intensity levels calculated using the moving epidemic method

Objectives

Although influenza-like illnesses (ILI) and acute respiratory illnesses (ARI) surveillance are well established in Europe, the comparability of intensity among countries and seasons remains an unresolved challenge. The objective is to compare the intensity of ILI and ARI in some European countries.

Design and setting

Weekly ILI and ARI incidence rates and proportion of primary care consultations were modeled in 28 countries for the 1996/1997–2013/2014 seasons using the moving epidemic method (MEM). We calculated the epidemic threshold and three intensity thresholds, which delimit five intensity levels: baseline, low, medium, high, and very high. The intensity of 2013/2014 season is described and compared by country.

Results

The lowest ILI epidemic thresholds appeared in Sweden and Estonia (below 10 cases per 100 000) and the highest in Belgium, Denmark, Hungary, Poland, Serbia, and Slovakia (above 100 per 100 000). The 2009/2010 season was the most intense, with 35% of the countries showing high or very high intensity levels. The European epidemic period in season 2013/2014 started in January 2014 in Spain, Poland, and Greece. The intensity was between low and medium and only Greece reached the high intensity level, in weeks 7 to 9/2014. Some countries remained at the baseline level throughout the entire surveillance period.

Conclusions

Epidemic and intensity thresholds varied by country. Influenza-like illnesses and ARI levels normalized by MEM in 2013/2014 showed that the intensity of the season in Europe was between low and medium in most of the countries. Comparing intensity among seasons or countries is essential for understanding patterns in seasonal epidemics. An automated standardized model for comparison should be implemented at national and international levels.     

2017-2018天津市流感季流感流行强度研究

目的 采用移动流行区间法(Moving epidemic method,MEM)判断流感活动开始和流感流行强度,为采取公共卫生措施提供理论依据。方法 以天津市2012-2017流感监测年度的流感病毒检测阳性率数据为基线,分析天津市2017-2018年流感季流感流行强度。结果 2017-2018年流感流行季,流感较去年同期(2016-2017年)提前3周进入流行状态。流感在2017年第45周突破流行阈值,持续4周后,第49周直接跨越中等流行进入高等流行,第50周进入非常高流行,并持续6周(2017年第50 ~52周,2018年第1~3周),2018年第4周跌至中等流行阶段,2018年第8周进入低等流行阶段,2018年第12周跌破流行阈值。结论 移动流行区间法,可以客观评价流感活动开始和流感流行强度,为比较国家与地区之间流感流行强度提供标准化方法。     

Primary care influenza‐like illness surveillance in Ho Chi Minh City,Vietnam 2013‐2015

Background

Year‐round transmission of influenza has been detected in Vietnam through both national surveillance and other epidemiological studies. Understanding the demographic and clinical features of influenza‐like illness (ILI) presenting to primary care in urban Vietnam is vital to understand these transmission dynamics.

Methods

An observational study of patients with ILI in Ho Chi Minh City, Vietnam, was conducted between August 2013 and November 2015 in a mix of public and private primary care settings. Molecular testing for influenza A and influenza B and 12 other respiratory viruses was performed.

Results

A total of 1152 ILI patients were recruited. 322 and 136 subjects tested positive for influenza A and influenza B, respectively. 193 subjects tested positive for another respiratory virus; most commonly rhinovirus and parainfluenza virus 3. Influenza was detected in 81% of the 116 study weeks. Three peaks of influenza activity were detected; an H3N2 peak April‐June 2014, an influenza B peak July‐December 2014, and a mixed H3N2 and H1N1 peak March‐September 2015. Subjects recruited from private clinics were more likely to have higher income and to have reported previous influenza vaccination. Antibiotic use was common (50.3%) despite limited evidence of bacterial infection.

Conclusion

Influenza in southern Vietnam has complex transmission dynamics including periods of intense influenza activity of alternating types and subtypes. Broadening surveillance from hospital to the community in tropical settings is feasible and a valuable for improving our understanding of the global spread and evolution of the virus.     

Fluwatchers A Crowdsourcing Approach: FluWatchers: Evaluation of a crowdsourced influenza-like illness surveillance application for Canadian influenza seasons 2015–2016 to 2018–2019

BackgroundSentinel influenza-like illness (ILI) surveillance is an essential component of a comprehensive influenza surveillance program. Community-based ILI surveillance systems that rely solely on sentinel healthcare practices omit important segments of the population, including those who do not seek medical care. Participatory surveillance, which relies on community participation in surveillance, may address some limitations of traditional ILI systems.ObjectiveWe aimed to evaluate FluWatchers, a crowdsourced ILI application developed to complement and complete ILI surveillance in Canada.MethodsUsing established frameworks for surveillance evaluations, we assessed the acceptability, reliability, accuracy and usefulness of the FluWatchers system 2015–2016, through 2018–2019. Evaluation indicators were compared against national surveillance indicators of ILI and of laboratory confirmed respiratory virus infections.ResultsThe acceptability of FluWatchers was demonstrated by growth of 50%–100% in season-over-season participation, and a consistent season-over-season retention of 80%. Reliability was greater for FluWatchers than for our traditional ILI system, although both systems had week-over-week fluctuations in the number of participants responding. FluWatchers’ ILI rates had moderate correlation with weekly influenza laboratory detection rates and other winter seasonal respiratory virus detections including respiratory syncytial virus and seasonal coronaviruses. Finally, FluWatchers has demonstrated its usefulness as a source of core FluWatch surveillance information and has the potential to fill data gaps in current programs for influenza surveillance and control.ConclusionFluWatchers is an example of an innovative digital participatory surveillance program that was created to address limitations of traditional ILI surveillance in Canada. It fulfills the surveillance system evaluation criteria of acceptability, reliability, accuracy and usefulness.     

Hospitalization of influenza‐like illness patients recommended by general practitioners in France between 1997 and 2010

Please cite this paper as: Pelat et al. (2012) Hospitalization of influenza‐like illness patients recommended by general practitioners in France between 1997 and 2010. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00356.x. Background The case–hospitalization ratio (CHR) is a key quantity for the management of emerging pathogens such as pandemic influenza. Yet, few running surveillance systems prospectively monitor the CHR during influenza epidemics. Here, we analyze the proportion of recommended hospitalizations (PRH) among influenza‐like illness (ILI) patients attended in general practice in France and compare the PRH observed during the 2009–2010 A(H1N1) pandemic with the one of the twelve previous seasons. Methods ILI cases were recorded by general practitioners (GPs) involved in surveillance, who indicated for each case whether they recommended hospitalization. We stratify the analysis by age, sex, and viral subtype. We investigate the reasons why GPs recommended hospitalization and the presence of risk factors for pandemic A(H1N1) complications. Results The average PRH over the seasons 1997–1998 to 2008–2009 was 3·4‰ (3–3·9). It was three times higher during the 2009–2010 pandemic than during seasonal influenza epidemics (OR = 2·89, 95% CI: 2·28–3·64). The highest increase was among 20–39‐year‐old women: OR = 11·8 (5·04–29·59). Overall, the principal reasons for recommending hospitalization were “respiratory problems” and “bad general condition.” However, during the pandemic, “age” (mainly associated with infants), “pregnancy,” and “diagnostic” became more frequent than before (P < 0·001). Finally, pregnancy was the reported risk factor for pandemic A(H1N1) complications that had the largest impact on hospitalization recommendation during the pandemic (OR = 38·62, P < 0·001). Conclusion Easily implemented in surveillance systems, this protocol has the potential to reveal changes in hospitalization recommendation by GPs. Moreover, if the right data are collected alongside, it could give timely insights into epidemic severity.     

2017—2018年北京市海淀区流行性感冒监测数据病原学分析

目的　对2017年1月—2018年12月北京市海淀区流行性感冒（流感）监测数据进行分析,了解海淀区流感的流行情况和趋势,为海淀区流感防控工作提供科学依据。方法　采集北京市海淀区国家级流感监测哨点医院2017—2018年的流感样病例咽拭子标本,采用实时荧光定量PCR方法进行流感病毒核酸检测。结果　2017—2018年共采集1743例咽拭子标本,检出流感病毒核酸阳性样本262例,阳性检出率为15.03%;2017年与2018年流感病毒核酸阳性检出率差异无统计学意义（P＞0.05）;男性流感病毒核酸阳性检出率高于女性（P＜0.05）;60岁及以上年龄组流感病毒核酸阳性检出率最高（P＜0.05）;冬、春季流感病毒核酸阳性检出率高于夏、秋季（P＜0.05）。结论　北京市海淀区在2017年与2018年流感流行强度较高,冬、春季为高峰季节,但2年流行的流感病毒优势株有所不同,老年病例流感病毒核酸阳性检出率最高,是流感防控重点人群,学校和托幼机构是聚集性疫情重点防控场所。     

Correlation between emergency room visits for influenza‐like illness during the influenza A (H1/N1) pandemic in children and adults

Surveillance of incident influenza‐like illness (ILI) was implemented in two children and adult medical emergency departments during the influenza A (H1/N1) pandemic to assess correlations in the daily number of ILI‐related emergency room visits (ERV) between these departments. A total of 7165 ILIs in children and 610 ILIs in adults were observed. We noticed a high linear correlation between the number of ERV involving ILI on day D in the pediatric department and the number of ERV because of ILI 2 days later in adults (R = 0·82, P < 10^?4). Therefore, the rate of adult ILI‐related ERV might be anticipated based on the rate of pediatric ERV.     

Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity

Please cite this paper as: Jhung et al. (2011) Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity. Influenza and Other Respiratory Viruses 5(5), 321–327. Background To augment established influenza surveillance systems in the United States, the Centers for Disease Control and Prevention and the Council of State and Territorial Epidemiologists implemented the Aggregate Hospitalization and Death Reporting Activity (AHDRA) in August 2009. The AHDRA was designed to meet increased demands for timely and detailed information describing illness severity during the 2009 H1N1 influenza A (pH1N1) pandemic response. Objectives We describe the implementation of AHDRA and provide preliminary results from this new surveillance activity. Methods All 50 US states were asked to report influenza‐associated hospitalizations and deaths to AHDRA each week using either a laboratory‐confirmed or syndromic surveillance definition. Aggregate counts were used to calculate age‐specific weekly and cumulative rates per 100 000, and laboratory‐confirmed reports were used to estimate the age distribution of pH1N1 influenza‐associated hospitalizations and deaths. Results From August 30, 2009, through April 6, 2010, AHDRA identified 41 689 laboratory‐confirmed influenza‐associated hospitalizations and 2096 laboratory‐confirmed influenza‐associated deaths. Aggregate Hospitalization and Death Reporting Activity rates peaked earlier than hospitalization and death rates seen in previous influenza seasons with other surveillance systems, and the age distribution of cases revealed a tendency for hospitalizations and deaths to occur in persons <65 years for age. Conclusions Aggregate Hospitalization and Death Reporting Activity laboratory‐confirmed reports provided important information during the 2009 pandemic response. Aggregate Hospitalization and Death Reporting Activity syndromic reports were marked by low representativeness and specificity and were therefore less useful. The AHDRA was implemented quickly and may be a useful surveillance system to monitor severe illness during future influenza pandemics.