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Influenza Other Respir Viruses. 2018 Nov 14. doi: 10.1111/irv.12620. [Epub ahead of print]
Influenza epidemics observed in primary care from 1984 to 2017 in France: a decrease of epidemic size over time.
Souty C1, Amoros P1, Falchi A2, Capai L1,2, Bonmarin I3, van der Werf S4,5,6,7, Masse S1,2, Turbelin C1, Rossignol L1, Vilcu AM1, L?vy-Bruhl D3, Lina B8,9, Minodier L2, Dorl?ans Y1, Guerrisi C1, Hanslik T1,10,11, Blanchon T1.
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Abstract
BACKGROUND:
Epidemiological analysis of past influenza epidemics remains essential to understand the evolution of the disease and optimize control and prevention strategies. Here, we aimed to use data collected by a primary care surveillance system over the last three decades to study trends in influenza epidemics and describe epidemic profiles according to circulating influenza viruses.
METHODS:
Influenza-like illness (ILI) weekly incidences were estimated using cases reported by general practitioners participating in the French Sentinelles network, between 1984 and 2017. Influenza epidemics were detected by applying a periodic regression to this time series. Epidemic (co-)dominant influenza virus (sub)types were determined using French virology data.
RESULTS:
During the study period, 297607 ILI cases were reported allowing the detection of 33 influenza epidemics. On average, seasonal epidemics lasted 9 weeks and affected 4.1% of the population (95%CI [3.5;4.7]). Mean age of cases was 29 years. Epidemic size decreased over time by -66 cases per 100000 population per season on average (95%CI [-132;-0.2], pval=0.049) and epidemic height decreased by -15 cases per 100000 (95%CI [-28;-2], pval=0.022). Epidemic duration appeared stable over time. Epidemics were mostly dominated by A(H3N2) (n=17, 52%), associated to larger epidemic size, higher epidemic peak and older age of cases.
CONCLUSIONS:
The declining trend in influenza epidemic size and height over the last 33 years might be related to several factors like increased vaccine coverage, hygiene improvements or changing in influenza viruses. However, further researches are needed to assess the impact of potential contributing factors to adapt influenza plans. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
KEYWORDS:
epidemics; influenza; influenza-like illness; primary care; surveillance
PMID: 30428158 DOI: 10.1111/irv.12620
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Influenza epidemics observed in primary care from 1984 to 2017 in France: a decrease of epidemic size over time.
Souty C1, Amoros P1, Falchi A2, Capai L1,2, Bonmarin I3, van der Werf S4,5,6,7, Masse S1,2, Turbelin C1, Rossignol L1, Vilcu AM1, L?vy-Bruhl D3, Lina B8,9, Minodier L2, Dorl?ans Y1, Guerrisi C1, Hanslik T1,10,11, Blanchon T1.
Author information
Abstract
BACKGROUND:
Epidemiological analysis of past influenza epidemics remains essential to understand the evolution of the disease and optimize control and prevention strategies. Here, we aimed to use data collected by a primary care surveillance system over the last three decades to study trends in influenza epidemics and describe epidemic profiles according to circulating influenza viruses.
METHODS:
Influenza-like illness (ILI) weekly incidences were estimated using cases reported by general practitioners participating in the French Sentinelles network, between 1984 and 2017. Influenza epidemics were detected by applying a periodic regression to this time series. Epidemic (co-)dominant influenza virus (sub)types were determined using French virology data.
RESULTS:
During the study period, 297607 ILI cases were reported allowing the detection of 33 influenza epidemics. On average, seasonal epidemics lasted 9 weeks and affected 4.1% of the population (95%CI [3.5;4.7]). Mean age of cases was 29 years. Epidemic size decreased over time by -66 cases per 100000 population per season on average (95%CI [-132;-0.2], pval=0.049) and epidemic height decreased by -15 cases per 100000 (95%CI [-28;-2], pval=0.022). Epidemic duration appeared stable over time. Epidemics were mostly dominated by A(H3N2) (n=17, 52%), associated to larger epidemic size, higher epidemic peak and older age of cases.
CONCLUSIONS:
The declining trend in influenza epidemic size and height over the last 33 years might be related to several factors like increased vaccine coverage, hygiene improvements or changing in influenza viruses. However, further researches are needed to assess the impact of potential contributing factors to adapt influenza plans. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
KEYWORDS:
epidemics; influenza; influenza-like illness; primary care; surveillance
PMID: 30428158 DOI: 10.1111/irv.12620
Free full text