Five years of sentinel surveillance of acute respiratory infections (1985-1990): the benefits of an influenza early warning system

Genomic monitoring of SARS-CoV-2 variants using sentinel SARI hospital surveillance

Background

To support the COVID-19 pandemic response, many countries, including Belgium, implemented baseline genomic surveillance (BGS) programs aiming to early detect and characterize new SARS-CoV-2 variants. In parallel, Belgium maintained a sentinel network of six hospitals that samples patients with severe acute respiratory infections (SARI) and integrated SARS-CoV-2 detection within a broader range of respiratory pathogens. We evaluate the ability of the SARI surveillance to monitor general trends and early signals of viral genetic evolution of SARS-CoV-2 and compare it with the BGS as a reference model.

Methods

Nine-hundred twenty-five SARS-CoV-2 positive samples from patients fulfilling the Belgian SARI definition between January 2020 and December 2022 were sequenced using the ARTIC Network amplicon tiling approach on a MinION platform. Weekly variant of concern (VOC) proportions and types were compared to those that were circulating between 2021 and 2022, using 96,251 sequences of the BGS.

Results

SARI surveillance allowed timely detection of the Omicron (BA.1, BA.2, BA.4, and BA.5) and Delta (B.1.617.2) VOCs, with no to 2 weeks delay according to the start of their epidemic growth in the Belgian population. First detection of VOCs B.1.351 and P.1 took longer, but these remained minor in Belgium. Omicron BA.3 was never detected in SARI surveillance. Timeliness could not be evaluated for B.1.1.7, being already major at the start of the study period.

Conclusions

Genomic surveillance of SARS-CoV-2 using SARI sentinel surveillance has proven to accurately reflect VOCs detected in the population and provides a cost-effective solution for long-term genomic monitoring of circulating respiratory viruses.

Distinct influenza surveillance networks and their agreement in recording regional influenza circulation: Experience from Southeast Michigan

INTRODUCTION

In Southeast Michigan, active surveillance studies monitor influenza activity in hospitals, ambulatory clinics, and community households. Across five respiratory seasons, we assessed the contribution of data from each of the three networks towards improving our overall understanding of regional influenza circulation.

METHODS

All three networks used case definitions for acute respiratory illness (ARI) and molecularly tested for influenza from research-collected respiratory specimens. Age- and network-stratified epidemic curves were created for influenza A and B. We compared stratified epidemic curves visually and by centering at seasonal midpoints.

RESULTS

Across all seasons (from 2014/2015 through 2018/2019), epidemic curves from each of the three networks were comparable in terms of both timing and magnitude. Small discrepancies in epidemics recorded by each network support previous conclusions about broader characteristics of particular influenza seasons.

CONCLUSION

Influenza surveillance systems based in hospital, ambulatory clinic, and community household settings appear to provide largely similar information regarding regional epidemic activity. Together, multiple levels of influenza surveillance provide a detailed view of regional influenza epidemics, but a single surveillance system-regardless of population subgroup monitored-appears to be sufficient in providing vital information regarding community influenza epidemics.

Spotlight influenza: The 2019/20 influenza season and the impact of COVID-19 on influenza surveillance in the WHO European Region

BackgroundAnnual seasonal influenza activity in the northern hemisphere causes a high burden of disease during the winter months, peaking in the first weeks of the year.AimWe describe the 2019/20 influenza season and the impact of the COVID-19 pandemic on sentinel surveillance in the World Health Organization (WHO) European Region.MethodsWe analysed weekly epidemiological and virological influenza data from sentinel primary care and hospital sources reported by countries, territories and areas (hereafter countries) in the European Region.ResultsWe observed co-circulation of influenza B/Victoria-lineage, A(H1)pdm09 and A(H3) viruses during the 2019/20 season, with different dominance patterns observed across the Region. A higher proportion of patients with influenza A virus infection than type B were observed. The influenza activity started in week 47/2019, and influenza positivity rate was ≥ 50% for 2 weeks (05-06/2020) rather than 5-8 weeks in the previous five seasons. In many countries a rapid reduction in sentinel reports and the highest influenza activity was observed in weeks 09-13/2020. Reporting was reduced from week 14/2020 across the Region coincident with the onset of widespread circulation of SARS-CoV-2.ConclusionsOverall, influenza type A viruses dominated; however, there were varying patterns across the Region, with dominance of B/Victoria-lineage viruses in a few countries. The COVID-19 pandemic contributed to an earlier end of the influenza season and reduced influenza virus circulation probably owing to restricted healthcare access and public health measures.

Classification of Spatiotemporal Data for Epidemic Alert Systems: Monitoring Influenza-Like Illness in France

Surveillance data used by epidemic alert systems are typically fully aggregated in space at the national level. However, epidemics may be spatially heterogeneous, undergoing distinct dynamics in distinct regions of the surveillance area. We unveiled this in retrospective analyses by classifying incidence time series. We used Pearson correlation to quantify the similarity between local time series and then classified them using modularity maximization. The surveillance area was thus divided into regions with different incidence patterns. We analyzed 31 years (1985-2016) of data on influenza-like illness from the French Sentinelles system and found spatial heterogeneity in 19 of 31 influenza seasons. However, distinct epidemic regions could be identified only 4-5 weeks after a nationwide alert. The impact of spatial heterogeneity on influenza epidemiology was complex. First, when a nationwide alert was triggered, 32%-41% of the administrative regions of France were experiencing an epidemic, while the others were not. Second, the nationwide alert was timely for the whole surveillance area, but subsequently regions experienced distinct epidemic dynamics. Third, the epidemic dynamics were homogeneous in space. Spatial heterogeneity analyses can provide information on the timing of the peak and end of the epidemic, in various regions, for use in tailoring disease monitoring and control.

Availability of informal caregivers in surviving stroke patients in Belgium

OBJECTIVE

To quantify the availability of informal caregivers in surviving stroke patients residing at home in Belgium.

METHODS

National estimates on the availability of informal caregivers were made using data from a nationwide observational registration of family physicians working in sentinel practices and a nationwide administrative database for reimbursement of hospitals in Belgium.

RESULTS

A total of 189 Belgian family physicians (FPs) from 141 practices participated in the study and recorded 326 patients (144 men and 182 women) with stroke. These FPs reach 1.5% of the Belgian population. After 1 month, 71% of the male and 75% of the female stroke survivors received support from family caregivers (p = 0.547). After 6 months, the percentage of male patients who received support from family caregivers decreased to 60% compared with 75% in female (p = 0.038). Of all patients with stroke admitted to Belgian hospitals during the reference year 2009 (n = 16.437), 8.997 returned home. Based on the findings from the sentinel practices, it is estimated that a mean of 73% (n = 6.568) and 67.5% (n = 6.073) of surviving patients with stroke can rely on informal caregivers in their home setting after one and 6 months, respectively.

CONCLUSIONS

A vast majority of surviving stroke patients in Belgium can rely on informal caregivers in their home setting, but their availability rapidly decreases 6 months after the event. These findings underline the importance of proactive health policy making in stroke care taking into account the potentially decreasing number of available informal caregivers in the decades to come.

Physician privacy concerns when disclosing patient data for public health purposes during a pandemic influenza outbreak

Background

Privacy concerns by providers have been a barrier to disclosing patient information for public health purposes. This is the case even for mandated notifiable disease reporting. In the context of a pandemic it has been argued that the public good should supersede an individual's right to privacy. The precise nature of these provider privacy concerns, and whether they are diluted in the context of a pandemic are not known. Our objective was to understand the privacy barriers which could potentially influence family physicians' reporting of patient-level surveillance data to public health agencies during the Fall 2009 pandemic H1N1 influenza outbreak.

Methods

Thirty seven family doctors participated in a series of five focus groups between October 29-31 2009. They also completed a survey about the data they were willing to disclose to public health units. Descriptive statistics were used to summarize the amount of patient detail the participants were willing to disclose, factors that would facilitate data disclosure, and the consensus on those factors. The analysis of the qualitative data was based on grounded theory.

Results

The family doctors were reluctant to disclose patient data to public health units. This was due to concerns about the extent to which public health agencies are dependable to protect health information (trusting beliefs), and the possibility of loss due to disclosing health information (risk beliefs). We identified six specific actions that public health units can take which would affect these beliefs, and potentially increase the willingness to disclose patient information for public health purposes.

Conclusions

The uncertainty surrounding a pandemic of a new strain of influenza has not changed the privacy concerns of physicians about disclosing patient data. It is important to address these concerns to ensure reliable reporting during future outbreaks.

Epidemics of influenza and pediatric diseases observed in infectious disease surveillance in Japan, 1999-2005

BACKGROUND

A method for determining epidemics in small areas from the sentinel surveillance data has been proposed and applied in the National Epidemiological Surveillance of Infectious Diseases (NESID) in Japan. We observed epidemics of influenza and 11 pediatric diseases by the method in the NESID in Japan during 1999-2005.

METHODS

We assumed that an epidemic in a public health center area began in a week when the number of cases reported to the NESID per sentinel clinic and hospital in the area in the week exceeded a given value, and that the epidemic ended when the number was lower than another given value. The proportion of public health center areas with epidemics (epidemic area proportion) by week in fiscal 1999-2005 was calculated. Total public health center area-weeks observed were about 30,000 each year.

RESULTS

The mean epidemic area proportion in the 7 years was 6.0% for influenza and 0.2-7.4% for pediatric diseases. The proportion increased in pharyngoconjunctival fever and group A streptococcal pharyngitis, decreased in measles and was less than 1.0% in pertussis and rubella. In influenza, the height of the peak in the weekly epidemic area proportion varied between 6 and 90% in the 7 years and the week of the peak varied widely. In some pediatric diseases, the height of the peak varied, while the week of the peak was relatively constant.

CONCLUSION

The frequency and temporal change were described in the epidemics of influenza and pediatric diseases in public health center areas from the NESID data in Japan, 1999-2005.

Wide-area epidemics of influenza and pediatric diseases from infectious disease surveillance in Japan, 1999-2005

BACKGROUND

Epidemics of infectious diseases usually start in small areas and subsequently become widespread widely. Although a method for detecting epidemics in public health center (PHC) areas has been proposed and used in the National Epidemiological Surveillance of Infectious Diseases in Japan, wide-area epidemics have not been fully investigated.

METHODS

Using the abovementioned method, we defined an epidemic as that occurring for a week in at least one PHC area in a prefecture and a wide-area epidemic as that when the number of people living in epidemic PHC areas exceeds 30% of the prefectural population. The number of weeks of an epidemic or wide-area epidemic for influenza and 11 pediatric diseases was observed in 47 prefectures in Japan from 1999 through 2005.

RESULTS

Epidemics and wide-area epidemics of influenza occurred for an average of 7.0 and 4.3 weeks in a year in a prefecture, respectively. The proportion of wide-area epidemics in epidemic weeks was 62%. The average number of wide-area epidemic weeks for pediatric diseases varied among diseases; it was more than 4 weeks for infectious gastroenteritis and herpangina and less than 1 week for pertussis, rubella, and measles. The proportion of wide-area epidemics in epidemic weeks was 28-41% for infectious gastroenteritis, hand-foot-mouth disease, and herpangina and less than 20% for other diseases.

CONCLUSIONS

The frequency of wide-area epidemics of influenza and pediatric diseases in various prefectures was observed. Epidemics of infectious diseases such as influenza and herpangina occurring in small areas were likely to spread to wide areas.

[General practice and surveillance: the example of influenza in France]

Data registration by the GROG national network (Regional Group for the Surveillance of Influenza) since 1984 has helped to identify methodological problems. The choice of sentinels and the selection of indicators depend on the analysis of actual influenza consequences. Various sentinels may be concerned: health insurance companies, private companies, schools, physicians, pharmacists. Health care organization modifies the validity of indicators. In France, for instance, home visits were an excellent indicator for early warning before 1995 but this indicator is no longer as efficient as before. The virological detection of Influenza depends on the organization of transportation (samples, results). The predictive value of cases definitions depends on the incidence of infection. The level of choice between specificity and sensibility modifies the perception of outbreaks. Sentinel participation rate influences the sample representativity. The farther this rate is from 100%, the more result validity decreases (in the same way that patients lost to follow-up compromise the validity of results in clinical trials). The publication of results can modify health expenses and behaviors.

CONCLUSION

The GROG network stresses the important role that general practitioners play in health surveillance; it also raises questions in the field of mathematics, statistics, professional organization, training, education, and politics.

Evaluation of a method for issuing warnings pre-epidemics and epidemics in Japan by infectious diseases surveillance

BACKGROUND: Simple methods have been developed to warn of pre-epidemics and epidemics in small areas using data of infectious diseases surveillance. Epidemic warnings are made if the index of cases per week per sentinel medical institution is greater than a defined value. A pre-epidemic warning means that an epidemic warning will be given in the following four weeks. While the methods are used routinely for surveillance in Japan, they remain to be validated.

METHODS: Infectious diseases surveillance data of influenza-like illness and 12 pediatric diseases in the fiscal year between 1999 and 2001 were used in the analysis. We examined the frequency of warnings, temporal changes in the index before and after the onset of a warning, and the sensitivity, specificity, and positive predictive value of pre-epidemic warnings.

RESULTS: For the majority of the diseases investigated, the proportion of weeks in which a warning was issued ranged between 0% and 10%. In several diseases including influenza-like illness, we observed a rapid increase and gradual decrease in the index before and after a warning. The sensitivity, specificity, and positive predictive value of a pre-epidemic warning were 90.4%, 93.7% and 23.9% for influenza-like illness, and ranged between 25.1-54.2%, 86.1-99.2%, and 2.5-20.8% for the pediatric diseases (chickenpox, rubella, measles, and mumps), respectively.

CONCLUSIONS: The study showed that the methods used for determining whether or not to issue an epidemic warning were satisfactory in some diseases, including influenza-like illness, and may need to be improved in several other diseases.

Detection of epidemics in their early stage through infectious disease surveillance

BACKGROUND

Surveillance of infectious diseases is done in many countries. The aims of such surveillance include the detection of epidemics. In the present study, the possibility of detecting an epidemic in its early stage using a simple method was evaluated for 16 infectious diseases.

METHODS

We used as an index the number of cases per week per sentinel medical institution in the area covered by a health centre in infectious disease surveillance in Japan in 1993-1997. Periods of epidemics in health centre areas were determined according to the reported indices. The simple method used for detecting the early stage of an epidemic is that if the index exceeds a critical value, then an epidemic will begin in the following 4 weeks. The sensitivity, specificity and positive predictive value for this epidemic warning were evaluated for given critical values.

RESULTS

When the specificity of the epidemic warning was more than 95%, the sensitivity was more than 60% in ten diseases, and more than 80% in four diseases (influenza-like illness, rubella, hand-foot-and-mouth disease, and herpangina). The positive predictive value was between 15.6% and 31.4% in these ten diseases.

CONCLUSION

The early stage of epidemics of some infectious diseases might be detectable using this simple method.

Survey on influenza laboratory diagnostic and surveillance methods in Europe. European Scientific Working Group on Influenza

The survey was undertaken by ESWI in order to investigate the comparability of the laboratory diagnostic methods and the influenza surveillance systems used in 24 European countries. The results indicate considerable consensus in the general approaches to collection and use of clinical specimens, rapid diagnostic techniques, virus isolation techniques in eggs or/and MDCK cell lines, virus identification and use of inhibition of hemagglutination (IHA) and complement fixation (CF) tests for serological diagnostics. However, the details of the techniques used are somewhat heterogeneous: antigen detection methods (immunofluorescence versus immuno adsorbent assay), isolation methods (eggs versus tissue culture), reagents (locally produced, WHO, commercial) are not always equivalent and results are therefore not really comparable. Some of these discrepancies are due to a lack of resources or a lack of priority for influenza in the country. The greatest differences between individual countries exist in the epidemiological part of surveillance programmes. The mode of collection of influenza related mortality and absentism from work varies considerably in different countries. These findings indicate the need to harmonize viral procedures and surveillance systems in European countries in order to improve validity and comparability of results and as a prerequisite for early information on influenza etiology and spread.

Forecasting disease risk for increased epidemic preparedness in public health

Emerging infectious diseases pose a growing threat to human populations. Many of the world's epidemic diseases (particularly those transmitted by intermediate hosts) are known to be highly sensitive to long-term changes in climate and short-term fluctuations in the weather. The application of environmental data to the study of disease offers the capability to demonstrate vector-environment relationships and potentially forecast the risk of disease outbreaks or epidemics. Accurate disease forecasting models would markedly improve epidemic prevention and control capabilities. This chapter examines the potential for epidemic forecasting and discusses the issues associated with the development of global networks for surveillance and prediction. Existing global systems for epidemic preparedness focus on disease surveillance using either expert knowledge or statistical modelling of disease activity and thresholds to identify times and areas of risk. Predictive health information systems would use monitored environmental variables, linked to a disease system, to be observed and provide prior information of outbreaks. The components and varieties of forecasting systems are discussed with selected examples, along with issues relating to further development.

The plea against annual influenza vaccination? 'The Hoskins' Paradox' revisited

Three papers by Hoskins and collaborators published in The Lancet in the 70s, have been challenging the common policy to annually vaccinate people at risk with inactivated influenza virus vaccine. From an analysis of a vaccination campaign in adolescent pupils of a boarding school and four influenza outbreaks in the period 1970-76, Hoskins et al. concluded that annually repeated vaccinations would not confer protection against epidemic influenza in the long-term ('Hoskins' Paradox'). A review of the papers revealed, however, that most of the study subjects were not consequently vaccinated every year and that most of the presented data were, therefore, not relevant for the problem of annually repeated influenza vaccination. When applying strict definitions of single vaccination (immunised immediately prior to the epidemic, but not in the years before) and multiple vaccination (immunised immediately prior to the epidemic, and also in the year(s) before), only two of four epidemics (A/England/42/72 (H3N2) in 1972/73 and A/Port Chalmers/1/73 (H3N2) in 1973/74) could be evaluated: in one case, no negative effect of repeated vaccination could be detected, in the second case, the attack rate difference between groups with single and multiple vaccination was of borderline significance. Data on two other epidemics (B/Hong Kong/8/73 in 1973/74 and A/Victoria/3/75 (H3N2) in 1975/76) could not be interpreted because of incomplete vaccination strategies. In conclusion, Hoskins' Paradox cannot be substantiated by Hoskins' own data. Considering other published data on the subject, it is suggested that no negative effect of annually repeated vaccination on protection against epidemic influenza exists.

Multiplex reverse transcription-PCR for surveillance of influenza A and B viruses in England and Wales in 1995 and 1996

Multiple-target (multiplex) reverse transcription-PCR (RT-PCR) for detection, typing, and subtyping of the hemagglutinin gene of influenza type A (H3N2 and H1N1) and type B viruses was developed and applied prospectively to virological surveillance of influenza in England in the 1995-1996 winter season. During this season both influenza A H3N2 and H1N1 viruses were circulating, although at different times. Six hundred nineteen combined nose and throat swabs taken by general practitioners in sentinel practices from individuals presenting with "influenzalike illness" were analyzed by culture, multiplex RT-PCR, and immunofluorescence. Of the 619 samples, 246 (39.7%) were positive by multiplex RT-PCR compared with 200 (32.3%) which yielded influenza viruses on culture. There was 100% correlation between multiplex RT-PCR typing and subtyping and the influenza types and subtypes obtained from culture. There was also excellent correlation between the temporal detection of influenza A H3N2 and H1N1 viruses by multiplex RT-PCR and by culture. During the peak weeks of influenza virus activity, a total of 259 specimens were received, of which 101 (38.9%) yielded influenza viruses on culture while 149 (57.5%) were positive in multiplex RT-PCR, providing an increase in detection of influenza viruses of approximately 20%. The increased detection of influenza virus occurred in all the age groups sampled. Samples which were positive by multiplex RT-PCR but negative by culture were not detected significantly earlier or later in the winter of 1995-1996 but were detected during the peak weeks of clinical influenza virus activity. Multiplex RT-PCR was successfully used in surveillance of influenza to provide accurate, sensitive diagnosis directly on clinical specimens sent through the post.

Monitoring mortality as an indicator of influenza in Catalonia, Spain

STUDY OBJECTIVE

This study aimed to investigate the behaviour of two indicators of influenza activity in the area of Barcelona and to evaluate the usefulness of modelling them to improve the detection of influenza epidemics.

DESIGN

Descriptive time series study using the number of deaths due to all causes registered by funeral services and reported cases of influenza-like illness. The study concentrated on five influenza seasons, from week 45 of 1988 to week 44 of 1993. The weekly number of deaths and cases of influenza-like illness registered were processed using identification of a time series ARIMA model.

SETTING

Six large towns in the Barcelona province which have more than 60,000 inhabitants and funeral services in all of them.

MAIN RESULTS

For mortality, the proposed model was an autoregressive one of order 2 (ARIMA (2,0,0)) and for morbidity it was one of order 3 (ARIMA (3,0,0)). Finally, the two time series were analysed together to facilitate the detection of possible implications between them. The joint study of the two series shows that the mortality series can be modelled separately from the reported morbidity series, but the morbidity series is influenced as much by the number of previous cases of influenza reported as by the previous mortality registered.

CONCLUSIONS

The model based on general mortality is useful for detecting epidemic activity of influenza. However, because there is not an absolute gold standard that allows definition of the beginning of the epidemic, the final decision of when it is considered an epidemic and control measures recommended should be taken after evaluating all the indicators included in the influenza surveillance programme.

Influenza surveillance: experiences from establishing a sentinel surveillance system in Germany

OBJECTIVES

Before and during peak influenza periods there is increased morbidity from other respiratory tract disorders. Sentinel networks of primary care physicians can be very effective in the early detection of influenza epidemics and the German network, the Arbeitsgemeinschaft Influenza (AGI), began its work in this area in 1992.

METHODS

Data are transmitted weekly from the doctor's computer via Btx to a central computer. The numerator is the weekly number of acute respiratory infections (ARI) in five age groups and the denominator is the weekly number of patient consultations. Data on hospitalisation, mortality, and days of sick leave from work or school are also collected. Swabs for influenza specimens are collected in 30 physicians' offices each Monday and sent to three reference centres.

FINDINGS

During the last recording period, from week 46 1993 to week 15 1994, 411 physicians' offices participated in the network. For 16 to 22 weeks, more than 60% of the participants transmitted data. During both the 1992-93 and 1993-94 influenza seasons, peaks were observed in the rate of ARI. There was a corresponding increase in sick leave from work and school. Rates for hospitalisation and deaths due to influenza showed no peaks during either season.

CONCLUSIONS

Although the German sentinel network for influenza experienced some technical problems in the first year, it was possible to solve these. Reporting rates were very satisfactory in the second year. The network will now be expanded to include 750 physicians in order to receive 600 weekly reports and obtain a solid baseline for an early warning system.

Respiratory illness and mortality in England and Wales. A study of the relationships between weekly data for the incidence of respiratory disease presenting to general practitioners, and registered deaths

The possible relationship between the incidence of respiratory diseases as reported to general practitioners and numbers of registered deaths in England and Wales has been examined. Morbidity data from sentinel practices for the period 1986-1990 (population covered increased from 220,000 to 470,000) were used to calculate weekly rates of aggregated respiratory disease for persons of all ages and for elderly persons (aged 65 years and over). The elderly respiratory disease rates and numbers of deaths were aggregated into 4-week periods; secular and seasonal trends were removed from each series and the two sets of residuals were examined graphically and cross correlation coefficients calculated. There was a very strong positive association between the respiratory disease rate and number of deaths in the same 4-week period and there was also a significant but less pronounced association between respiratory disease in one 4-week period and deaths in the next. After prior separation of weeks according to temperature into four bands, weekly rates for respiratory disease were also strongly associated with the number of weekly deaths for each temperature band. The synchronisation of peaks and troughs in the two series throughout the year supports the hypothesis that a cause and effect relationship exists between respiratory disease in the elderly and number of deaths. Other climatic and meteorological variables besides temperature may play a part in determining the spread of a respiratory disease. There is a for further research to identify the micro-organisms responsible for acute respiratory infections in the elderly.