Strengthening influenza surveillance systems: The contribution of epidemiological and burden of disease data

Surveillance systems appear to be a crucial tool to monitor the evolution of epidemics. The thesis provides recommendations for strengthening influenza surveillance systems based on findings from five real-world evidence studies: an assessment of the quality of country influenza surveillance systems, a prospective surveillance study in a large hospital, a retrospective analysis of national hospital discharge databases, and a descriptive analysis of influenza in children, included in the placebo arm of a vaccine efficacy randomized controlled trial. In chapter 2, three national influenza surveillance systems in Asia were compared and their adherence to World Health Organization (WHO) guidance. Experts issued recommendations for their improvement. Recommendations encompasses introducing new surveillance tools, broadening the use of specific existing tools, collecting and sharing data on virus characteristics, developing immunization status registries, improving public health communication. In chapter 3, we examined influenza virus circulation in countries in the Asia-Pacific region and compared with the timing of influenza vaccination. Data were obtained from the WHO FluNet database for 2010–2017 from 19 countries. Peak circulation coincided with the winter seasons in most countries, although patterns were less clear in the inter-tropical area. The WHO-recommended timing for influenza vaccination was appropriate in 12 countries, inappropriate in 3 countries and inconclusive for 4 countries due to unclear seasonality of influenza virus circulation. In chapter 4, we analyzed local surveillance data based on a prospective surveillance study at the Hospital Edouard Herriot in Lyon, France over 11 years, and estimated the incidence and trends of hospital-acquired laboratory confirmed influenza infections among adult. An advanced age and an underlying disease were important characteristics of HAI. HAI occurred at a rate of 1 in 13 with influenza-like-illness in hospital. The HAI incidence was the highest in the geriatric ward and increased over time. HAI rates approximated hospital onset Clostridium difficile reported rates. In chapter 5, we examined the occurrence and burden of influenza in healthy children using data from a phase III placebo-controlled influenza vaccine trial. Data from 2,210 participants were analysed. The overall influenza attack rate was 11.5%. The most common influenza virus was A(H3N2) (40.7%), followed by B/Yamagata (23.6%), A(H1N1) (18.6%), and B/Victoria (8.0%). Grade 3 fever was reported in 24.3% of confirmed episodes, acute lower respiratory infection in 8.7%, acute otitis media in 6.1%, and pneumonia in 1.9%. Antibiotics were prescribed for 41.4% of influenza episodes. More than half of the episodes (57.0%) resulted in outpatient visits and for 1.1% of episodes in hospitalization. In chapter 6, we characterized the cumulative risk of comorbidities and age on severe outcomes in Mexico and Brazil. We used national hospital discharge data from Brazil (SIH/SUS) from 2010-2018 and Mexico (SAEH) from 2010-2017 to estimate the number of influenza admissions using ICD-10 discharge codes. In Brazil, the median duration of hospital stay was 3.0 days, ICU admission rate was 3.3%, and in-hospital Case fatality rate was 4.6% (95% CI, 4.5-4.7). In Mexico, the median duration of stay was 5.0 days, ICU admission rate was 1.8%, and in-hospital CFR was 6.9%. We found that age and comorbidities, especially cardiovascular disease, are cumulatively associated with more severe outcomes. In chapter 7 the main findings are discussed. National or regional surveillance data should be used to inform who and when to vaccinate and which vaccines to use in order to consider epidemiological and demographics countries’ variability. Priority target groups for influenza vaccination should be defined based on evidence about burden of disease and characteristics of the circulating virus. While we are still fighting the Covid-19 pandemic, our knowledge of influenza surveillance systems and their capacities should integrate surveillance of the main respiratory viral infections

Important changes in the timing of influenza epidemics in the WHO European Region over the past 20 years: Virological surveillance 1996 to 2016

Introduction: The global epidemiology of many infectious diseases is changing, but little attention has been paid to whether the timing of seasonal influenza epidemics changed in recent years. This study investigated whether the timing of the peak of influenza epidemics has changed in countries of the World Health Organization (WHO) European Region between 1996 and 2016. Methods: Surveillance data were obtained from the WHO FluNet database. For each country and season (July to June of the next year), the peak was defined as the week with the highest 3-week moving average for reported cases. Linear regression models were used to test for temporal trends in the timing of the epidemic peak in each country and to determine whether this differed geographically. Results: More than 600,000 influenza cases were included from 38 countries of the WHO European Region. The timing of the epidemic peak changed according to a longitudinal gradient, occurring progressively later in Western Europe (e.g. by 2.8 days/season in Spain) and progressively earlier in Eastern Europe (e.g. by 3.5 days/season in the Russian Federation). Discussion: These results were confirmed in several sensitivity analyses. Our findings have implications for influenza control and prevention measures in the WHO European Region, for instance for the implementation of influenza vaccination campaigns

Incidence of hospital-acquired influenza in adults: A prospective surveillance study from 2004 to 2017 in a French tertiary care hospital

Background: Hospital-acquired influenza potentially leads to significant morbidity and mortality in already vulnerable patients, but its overall burden is not fully understood. We undertook this study to estimate the incidence and trends of hospital-acquired laboratory-confirmed influenza among adults, and to compare clinical characteristics between hospital-acquired and community-acquired influenza cases. Methods: This was a prospective surveillance study over 11 years of adults with influenza-like-illness (ILI) hospitalized in surgery, medicine and geriatric wards in a tertiary acute-care hospital in Lyon, France. Nasal swabs were systematically collected from those with ILI and tested for influenza by reverse transcriptase-polymerase chain reaction at the national influenza reference laboratory (Lyon, France). Results: Influenza was laboratory confirmed at a rate of 1 in 13 patients who developed ILI during their hospitalization. Having an underlying disease was an important characteristic of hospital-acquired ILI cases. Cardiovascular disease was the most frequent underlying condition in both influenza-positive and influenza-negative patients. Complications were more frequent for influenza-positive than influenza-negative patients. The influenza incidence rate was highest in the geriatric ward and increased over the study period. Conclusions: Hospital-acquired influenza poses a significant risk to already vulnerable patients. Longitudinal surveillance data are essential to support better recognition and monitoring of viral infections in hospitals

Epidemiology and burden of influenza in healthy children aged 6 to 35 months: analysis of data from the placebo arm of a phase III efficacy trial

Abstract Background Despite World Health Organization recommendations, in many countries young children are not targeted for influenza vaccination. To help inform influenza vaccination policy, we examined the occurrence and burden of influenza in healthy children aged 6 to 35 months using data from a recent phase III placebo-controlled influenza vaccine trial conducted in countries in the Northern and Southern Hemispheres. Methods This was an analysis of data from participants included in the placebo arm of a phase III clinical trial in healthy children aged 6 to 35 months (EudraCT no. 2013–001231-51). Included children had never been vaccinated for influenza and were observed for one influenza season. Outcome measures included the occurrence of influenza-like illness (ILI), laboratory-confirmed influenza, virus types/subtypes, severe symptoms and complications of confirmed influenza, and healthcare use associated with confirmed influenza. Results Data from 2210 participants were analysed. ILI was reported for 811 participants (36.7%). Of these, 255 participants (31.4%) had 263 virologically confirmed episodes of influenza. The overall influenza attack rate was 11.5%. The most common influenza virus detected was A(H3N2) (40.7%), followed by B/Yamagata (23.6%), A(H1N1) (18.6%), and B/Victoria (8.0%). Grade 3 fever was reported in 24.3% of confirmed episodes, acute lower respiratory infection in 8.7%, acute otitis media in 6.1%, and pneumonia in 1.9%. In most influenza episodes (93.2%), antipyretics, analgesics, or non-steroidal anti-inflammatory drugs were taken. Antibiotics were prescribed for 41.4% of influenza episodes. More than half of the influenza episodes (57.0%) resulted in outpatient visits. Influenza resulted in overnight hospitalisation in 1.1% of episodes. Conclusions Influenza is associated with a significant burden of disease in healthy children. This analysis also revealed that antibiotics continue to be frequently used for young children with influenza. Trial registration EudraCT no. 2013–001231-51

The impact of the SARS-CoV-2 pandemic on global influenza surveillance: Insights from 18 National Influenza Centers based on a survey conducted between November 2021 and March 2022

Background: National Influenza Centers (NICs) have played a crucial role in the surveillance of SARS-CoV-2. The FluCov project, covering 22 countries, was initiated to monitor the impact of the SARS-CoV-2 pandemic on influenza activity. Methods: This project consisted of an epidemiological bulletin and NIC survey. The survey, designed to assess the impact of the pandemic on the influenza surveillance system, was shared with 36 NICs located across 22 countries. NICs were invited to reply between November 2021 and March 2022. Results: We received 18 responses from NICs in 14 countries. Most NICs (76%) indicated that the number of samples tested for influenza decreased. Yet, many NICs (60%) were able to increase their laboratory testing capacity and the "robustness" (e.g., number of sentinel sites) (59%) of their surveillance systems. In addition, sample sources (e.g., hospital or outpatient setting) shifted. All NICs reported a higher burden of work following the onset of the pandemic, with some NICs hiring additional staff or partial outsourcing to other institutes or departments. Many NICs anticipate the future integration of SARS-CoV-2 surveillance into the existing respiratory surveillance system. Discussion: The survey shows the profound impact of SARS-CoV-2 on national influenza surveillance in the first 27 months of the pandemic. Surveillance activities were temporarily disrupted, whilst priority was given to SARS-CoV-2. However, most NICs have shown rapid adaptive capacity underlining the importance of strong national influenza surveillance systems. These developments have the potential to benefit global respiratory surveillance in the years to come; however, questions about sustainability remain

Comparison of influenza surveillance systems in Australia, China, Malaysia and expert recommendations for influenza control

Background: The Western Pacific Region (WPR) is exposed each year to seasonal influenza and is often the source of new influenza virus variants and novel pathogen emergence. National influenza surveillance systems play a critical role in detecting emerging viruses, monitoring influenza epidemics, improving public disease awareness and promoting pandemic preparedness, but vary widely across WPR countries. The aim of this study is to improve existing influenza surveillance systems by systematically comparing selected WPR influenza surveillance systems. Methods: Three national influenza surveillance systems with different levels of development (Australia, China and Malaysia) were compared and their adherence to World Health Organization (WHO) guidance was evaluated using a structured framework previously tested in several European countries consisting of seven surveillance sub-systems, 19 comparable outcomes and five evaluation criteria. Based on the results, experts from the Asia-Pacific Alliance for the Control of Influenza (APACI) issued recommendations for the improvement of existing surveillance systems. Results: Australia demonstrated the broadest scope of influenza surveillance followed by China and Malaysia. In Australia, surveillance tools covered all sub-systems. In China, surveillance did not cover non-medically attended respiratory events, primary care consultations, and excess mortality modelling. In Malaysia, surveillance consisted of primary care and hospital sentinel schemes. There were disparities between the countries across the 5 evaluation criteria, particularly regarding data granularity from health authorities, information on data representativeness, and data communication, especially the absence of publicly available influenza epidemiological reports in Malaysia. This dual approach describing the scope of surveillance and evaluating the adherence to WHO guidance enabled APACI experts to make a number of recommendations for each country that included but were not limited to introducing new surveillance tools, broadening the use of specific existing surveillance tools, collecting and sharing data on virus characteristics, developing immunization status registries, and improving public health communication. Conclusions: Influenza monitoring in Australia, China, and Malaysia could benefit from the expansion of existing surveillance sentinel schemes, the broadened use of laboratory confirmation and the introduction of excess-mortality modelling. The results from the evaluation can be used as a basis to support expert recommendations and to enhance influenza surveillance capabilities

Impact of COVID-19 on routine immunisation in South-East Asia and Western Pacific: Disruptions and solutions.

10.1016/j.lanwpc.2021.100140Lancet Reg Health West Pac10100140

Indicators of severity, complications, and major diagnoses at discharge.

<p>Indicators of severity, complications, and major diagnoses at discharge.</p