Influenza-like Illness Surveillance System Research Articles

Estimation of the quality of life effect of seasonal influenza infection in the UK with the internet-based Flusurvey cohort: an observational cohort study

BackgroundDespite the public health effect of seasonal influenza in the UK, population-wide estimates of the quality-adjusted life-year (QALY) loss associated with influenza do not exist. Such estimates are needed to quantify the overall disease burden, compare it with other diseases, and assess the cost-effectiveness of control measures. Since 2009, the Flusurvey—an internet-based community surveillance system for influenza-like illness—has been operating in the UK. UK residents are recruited through print and broadcast media, social media, and word of mouth. There were about 6000 registered participants during the 2012–13 season, during which we used the Flusurvey cohort to measure QALY loss associated with illness. MethodsEach week, participants were asked to report any symptoms and their health status. Participants were asked to score their health status on a scale of 0–100 (0 representing the worst health imaginable and 100 the best); this method has provided estimates of QALY loss that are consistent with those obtained with the more traditional EQ-5D during the 2009 influenza pandemic. The analysis presented is based on participants who completed the health score at least once when symptomatic and at least once when free of symptoms, allowing the effect of illness on quality of life to be measured in individuals. Results were stratified by age group (0–17, 18–44, 45–64, and ≥65 years) and by severity of symptoms (acute respiratory infection [ARI] and influenza-like illness [ILI]; appendix). FindingsIllness lasted longer for cases of ILI (median 9 days, IQR 6–15) than for ARI (6 days, 4–10) and increased somewhat with age (appendix). The median baseline health score, reported when individuals were free from symptoms, was 90 (IQR 83–95). Individuals with ILI reported low health scores (median 60, IQR 43–75; 1837 episodes); a small reduction was reported by those with ARI (80, 70–85; 1297 episodes). The scores were similar in different age groups. The mean loss of quality-adjusted life was about 2·0 days (SD 2·5) for ILI cases (median 1·1 days, IQR 0·5–2·6) and 0·6 days (SD 0·9) for ARI cases (median 0·3 days, IQR 0·1–0·7). The quality-adjusted life-day (QALD) loss was thus over three times higher for ILI than for ARI. The mean estimated ILI QALD loss was close to that estimated for influenza during the 2009 influenza pandemic (2·0 vs 2·7 days). QALD loss increased with age for both ARI and ILI (appendix) and was significantly higher in individuals experiencing fever (p<0·0001). There was weak evidence for an increase of QALD loss in smokers (p=0·07) but no association with being in a risk group (p=0·15) or being vaccinated (p=0·73). InterpretationThis internet-based approach opens the way for standardised and refined measure of the public health effect of seasonal influenza and other respiratory infections in the UK and elsewhere. However, the study has limitations: it was a non-random, self-selecting sample, in which children were under-represented, and the self-reported symptoms were not validated by a medical practitioner. FundingThe Flusurvey is funded by Epiwork as part of the EU Seventh Framework Programme. AC and SF are both funded by a Medical Research Council Career Development Award in Biostatistics. KE is funded by a Career Development Fellowship supported by the National Institute for Health Research. The views expressed in this publication are those of the authors and not necessarily those of the funders.

Evaluating the Feasibility and Participants’ Representativeness of an Online Nationwide Surveillance System for Influenza in France

The increasing Internet coverage and the widespread use of digital devices offer the possibility to develop new digital surveillance systems potentially capable to provide important aid to epidemiological and public health monitoring and research. In France, a new nationwide surveillance system for influenza-like illness, GrippeNet.fr, was introduced since the 2011/2012 season based on an online participatory mechanism and open to the general population. We evaluate the recruitment and participation of users to the first pilot season with respect to similar efforts in Europe to assess the feasibility of establishing a participative network of surveillance in France. We further investigate the representativeness of the GrippeNet.fr population along a set of indicators on geographical, demographic, socio-economic and health aspects. Participation was widespread in the country and with rates comparable to other European countries with partnered projects running since a longer time. It was not representative of the general population in terms of age and gender, however all age classes were represented, including the older classes (65+ years old), generally less familiar with the digital world, but considered at high risk for influenza complications. Once adjusted on demographic indicators, the GrippeNet.fr population is found to be more frequently employed, with a higher education level and vaccination rate with respect to the general population. A similar propensity to commute for work to different regions was observed, and no significant difference was found for asthma and diabetes. Results show the feasibility of the system, provide indications to inform adjusted epidemic analyses, and highlight the presence of specific population groups that need to be addressed by targeted communication strategies to achieve a higher representativeness in the following seasons.

Detection of mild to moderate influenza A/H7N9 infection by China’s national sentinel surveillance system for influenza-like illness: case series

Objective To characterise the complete case series of influenza A/H7N9 infections as of 27 May 2013, detected by China’s national sentinel surveillance system for influenza-like illness.Design Case series.Setting Outpatient clinics...

Electronic School Absenteeism Monitoring and Influenza Surveillance, Hong Kong

Electronic School Absenteeism Monitoring and Influenza Surveillance, Hong Kong

Short message service sentinel surveillance of influenza-like illness in Madagascar, 2008-2012

The revision of the International Health Regulations (IHR) and the threat of influenza pandemics and other disease outbreaks with a major impact on developing countries have prompted bolstered surveillance capacity, particularly in low-resource settings. Surveillance tools with well-timed, validated data are necessary to strengthen disease surveillance. In 2007 Madagascar implemented a sentinel surveillance system for influenza-like illness (ILI) based on data collected from sentinel general practitioners. Before 2007, Madagascar's disease surveillance was based on the passive collection and reporting of data aggregated weekly or monthly. The system did not allow for the early identification of outbreaks or unexpected increases in disease incidence. An innovative case reporting system based on the use of cell phones was launched in March 2007. Encrypted short message service, which costs less than 2 United States dollars per month per health centre, is now being used by sentinel general practitioners for the daily reporting of cases of fever and ILI seen in their practices. To validate the daily data, practitioners also report epidemiological and clinical data (e.g. new febrile patient's sex, age, visit date, symptoms) weekly to the epidemiologists on the research team using special patient forms. Madagascar's sentinel ILI surveillance system represents the country's first nationwide "real-time" surveillance system. It has proved the feasibility of improving disease surveillance capacity through innovative systems despite resource constraints. This type of syndromic surveillance can detect unexpected increases in the incidence of ILI and other syndromic illnesses.

Vigilancia sindrómica de la gripe en atención primaria, un instrumento complementario a las redes centinelas para períodos de elevada incidencia de gripe

ObjectiveEpidemiological data on influenza is essential for resource management when the incidence of the disease in the population is very high, but not easily available in real-time. The objective of this study was to evaluate the use of a syndromic surveillance system for influenza-like illness in Primary Care (ILIsPC) and assess its level of agreement with the epidemiological data from the Influenza Sentinel Network. LocalizationHealth centres and deputising medical services in the Balearic Islands. ParticipantsData from 122 epidemiological weeks for each system were included. Main measuresData from January 1, 2007 to January 31, 2010 were compared. ILIsPC rates were obtained from the diagnoses registered in electronic health records of Primary Care clinics and deputising medical services. Data from Sentinel Network were obtained from weekly epidemiological reports. Intraclass correlation coefficient was calculated and Bland – Altman plot constructed. ResultsThere was good agreement between both measures, with an intraclass correlation coefficient of 0.88 (95% CI: 0.83-0.91). After constructing a Bland-Altman plot, the precision between both rates was greater during the periods of the highest influenza incidence. ConclusionsWe believe that the syndromic surveillance system ILIsPC, provides access to very useful data in real-time, especially during periods of high influenza incidence, such as during epidemics or the recent pandemic.

Influenza virus circulation in Cambodia

Background The Cambodian National Influenza Center (NIC) was established in August 2006 for the purpose of documenting the dynamics of influenza disease and to virologically characterize the circulating strains. To continuously monitor influenza activity, a hospital-based sentinel surveillance system for ILI (influenza-like illness) with a weekly reporting and sampling scheme was initially established in five sites in 2006. In addition, hospitalbased surveillance of acute lower respiratory infection (ALRI) cases was established in 2 sites.

Automated detection of influenza-like illness using clinical surveillance markers at a Department of Veterans Affairs Medical Center

Background:Using demographic and clinical measures from emergency department evaluations, we developed an automated surveillance system for influenza-like illness (ILI).Methods:We selected a random sample of patients who were seen at the Durham, NC Veterans Affairs Medical Center between May 2002 and October 2009 with fever or a respiratory ICD-9 diagnosis code and divided this into subsets for system development and validation. Comprehensive chart reviews identified patients who met a standard case definition for ILI. Logistic regression models predicting ILI were fit in the development sample. We applied the parameter estimates from these models to the validation sample and evaluated their utility using receiver-operator characteristic analysis.Results:The models discriminated ILI very well in the validation sample; the C-statistics were >0.89.Conclusions:Risk estimates based on statistical models can be incorporated into electronic medical records systems to assist clinicians and could be used in real-time surveillance for disease outbreaks.

Surveillance of influenza in Iceland during the 2009 pandemic

In a pandemic setting, surveillance is essential to monitor the spread of the disease and assess its impact. Appropriate mitigation and healthcare preparedness strategies depend on fast and accurate epidemic surveillance data. During the 2009 influenza A(H1N1) pandemic, rapid improvements in influenza surveillance were made in Iceland. Here, we describe the improvements made in influenza surveillance during the pandemic , which could also be of great value in outbreaks caused by other pathogens. Following the raised level of pandemic influenza alert in April 2009, influenza surveillance was intensified. A comprehensive automatic surveillance system for influenza-like illness was developed, surveillance of influenza-related deaths was established and laboratory surveillance for influenza was strengthened. School absenteeism reports were also collected and compared with results from the automatic surveillance system. The first case of 2009 pandemic influenza A(H1N1) was diagnosed in Iceland in May 2009, but sustained community transmission was not confirmed until mid-August. The pandemic virus circulated during the summer and early autumn before an abrupt increase in the number of cases was observed in October. There were large outbreaks in elementary schools for children aged 6–15 years throughout the country that peaked in late October. School absenteeism reports from all elementary schools in Iceland gave a similar epidemiological curve as that from data from the healthcare system. Estimates of the proportion of the population infected with the pandemic virus ranged from 10% to 22%. This study shows how the sudden need for improved surveillance in the pandemic led to rapid improvements in data collection in Iceland. This reporting system will be improved upon and expanded to include other notifiable diseases, to ensure accurate and timely collection of epidemiological data.

Internet-based surveillance of Influenza-like-illness in the UK during the 2009 H1N1 influenza pandemic

BackgroundInternet-based surveillance systems to monitor influenza-like illness (ILI) have advantages over traditional (physician-based) reporting systems, as they can potentially monitor a wider range of cases (i.e. including those that do not seek care). However, the requirement for participants to have internet access and to actively participate calls into question the representativeness of the data. Such systems have been in place in a number of European countries over the last few years, and in July 2009 this was extended to the UK. Here we present results of this survey with the aim of assessing the reliability of the data, and to evaluate methods to correct for possible biases.MethodsInternet-based monitoring of ILI was launched near the peak of the first wave of the UK H1N1v influenza pandemic. We compared the recorded ILI incidence with physician-recorded incidence and an estimate of the true number of cases over the course of the epidemic. We also compared overall attack rates. The effect of using different ILI definitions and alternative denominator assumptions on incidence estimates was explored.ResultsThe crude incidence measured by the internet-based system appears to be influenced by individuals who participated only once in the survey and who appeared more likely to be ill. This distorted the overall incidence trend. Concentrating on individuals who reported more than once results in a time series of ILI incidence that matches the trend of case estimates reasonably closely, with a correlation of 0.713 (P-value: 0.0001, 95% CI: 0.435, 0.867). Indeed, the internet-based system appears to give a better estimate of the relative height of the two waves of the UK pandemic than the physician-recorded incidence. The overall attack rate is, however, higher than other estimates, at about 16% when compared with a model-based estimate of 6%.ConclusionInternet-based monitoring of ILI can capture the trends in case numbers if appropriate weighting is used to correct for differential response. The overall level of incidence is, however, difficult to measure. Internet-based systems may be a useful adjunct to existing ILI surveillance systems as they capture cases that do not necessarily contact health care. However, further research is required before they can be used to accurately assess the absolute level of incidence in the community.

Influenza activity in Cambodia during 2006-2008

BackgroundThere is little information about influenza disease among the Cambodian population. To better understand the dynamics of influenza in Cambodia, the Cambodian National Influenza Center (NIC) was established in August 2006. To continuously monitor influenza activity, a hospital based sentinel surveillance system for ILI (influenza like illness) with a weekly reporting and sampling scheme was established in five sites in 2006. In addition, hospital based surveillance of acute lower respiratory infection (ALRI) cases was established in 2 sites.MethodsThe sentinel sites collect weekly epidemiological data on ILI patients fulfilling the case definition, and take naso-pharyngeal specimens from a defined number of cases per week. The samples are tested in the Virology Unit at the Institut Pasteur in Phnom Penh. From each sample viral RNA was extracted and amplified by a multiplex RT-PCR detecting simultaneously influenza A and influenza B virus. Influenza A viruses were then subtyped and analyzed by hemagglutination inhibition assay. Samples collected by the ALRI system were tested with the same approach.ResultsFrom 2006 to 2008, influenza circulation was observed mainly from June to December, with a clear seasonal peak in October shown in the data from 2008.ConclusionInfluenza activity in Cambodia occurred during the rainy season, from June to December, and ended before the cool season (extending usually from December to February). Although Cambodia is a tropical country geographically located in the northern hemisphere, influenza activity has a southern hemisphere transmission pattern. Together with the antigenic analysis of the circulating strains, it is now possible to give better influenza vaccination recommendation for Cambodia.

Review of an Influenza Surveillance System, Beijing, People’s Republic of China

In 2007, a surveillance system for influenza-like illness (ILI) and virologic data was established in Beijing, China. The system tracked ILI and laboratory-confirmed influenza in 153 general hospitals from September 1, 2007, through April 30, 2008. To analyze the ILI surveillance data (weekly ILI rates and counts) and the effectiveness of the system, we used the US Centers for Disease Control and Prevention Early Aberration Reporting System. The data indicated that the highest rate of influenza isolation and the highest ILI count occurred in the first week of 2008. The system enabled us to detect the onset and peak of an epidemic.

Community transmission of influenza A (H1N1)v virus at a rock festival in Belgium, 2-5 July 2009

On 6 July 2009 the Belgian enhanced surveillance system for influenza-like illness among travellers returning from influenza A(H1N1)v affected areas detected a case linked to a rock festival which took place on 2-5 July. The health authorities implemented communication and control measures leading to the detection of additional cases. This paper describes the outbreak and its impact on the management of the influenza pandemic in Belgium.

Influenza A(H1N1)v virus infections in Belgium, May-June 2009

In response to the ongoing influenza A(H1N1)v pandemic, first detected in North America in April 2009, Belgium has set up an active surveillance system for influenza-like illness among travellers returning from affected areas. This communication describes the clinical and epidemiological features of the first 43 laboratory-confirmed cases in Belgium.