Burden of influenza, healthcare seeking behaviour and hygiene measures during the A(H1N1)2009 pandemic in France: a population based study

Abstract

BackgroundInfluenza surveillance systems do not allow the identification of the true burden of illness caused by influenza in the community because they are restricted to consulting cases. A study was conducted to estimate the incidence and the burden of self-defined influenza, and to describe healthcare seeking behavior for self-defined influenza during the A(H1N1)2009 pandemic in the French population.MethodsWe conducted a random-based retrospective cross-sectional telephone survey between May 2009 and April 2010 among a random sample of the French population.ResultsFor the 10 076 people included, 107 episodes of self-defined influenza were reported. The annual incidence of self-defined influenza was estimated at 13 942 cases per 100 000 inhabitants (CI95% 10 947 – 16 961), 62.1% (CI95% 50.5 – 72.5) of cases consulted a physician and 11.3% (CI95% 5.5 - 21.7) used a face mask. Following recommendations, 37.5% (CI95% 35.5 – 39.5) of people in the survey reported washing their hands more often during the pandemic season, and there was a positive association with being vaccinated against A(H1N1)2009 influenza, being a women, being a child (< 15 years) or living in a big city (≥ 100 000 inhabitants).ConclusionsSelf-defined influenza causes a significant burden of illness in the French population and is a frequent cause for consultation. These results allow a more accurate interpretation of influenza surveillance data and an opportunity to adapt future health education messages.

A prospective study on ambulatory care provided by primary care pediatricians during influenza season

“…It is to note that in our study, the number of ILI cases was based on practitioner’s medical visit, providing a more reliable information compared to previous studies [15,17]. …”

Detecting Signals of Seasonal Influenza Severity through Age Dynamics

“…Medical claims and ILINet data are both subject to physician biases regarding the demographics and seasonality of influenza and doctor’s office closures. They also have healthcare-seeking behavior biases; school-aged children have higher rates of healthcare-seeking behavior for ILI than adults (approximately 1.1 to 1.4 times higher) [51, 52, 53], which is why we adjust for these biases in both datasets (See Supplementary Methods). Nevertheless, differences in surveillance data biases and study period may explain scaling issues with retrospective classification and poor performance in early warning severity for ILInet data (Supplement Figure 10 c&d) Additional studies on age-specific disparities in health care insurance and access to care, especially in consideration of ongoing changes to the U.S. health care system, are needed to better quantify biases in medical claims data and our index.…”

Influenza epidemics observed in primary care from 1984 to 2017 in France: A decrease in epidemic size over time

“…Secondly, observed decrease in influenza incidence rates may also be related to behaviour changes in the population like changing lifestyles (reduced household size, less smoking, cleaner air) and hygiene improvements; which might have contributed to reduce the transmissibility of influenza viruses . Recently, the 2009 pandemic could have impacted hygiene habits as frequency of hand washing and use of alcohol‐based hand sanitizers which were strongly promoted during the epidemic period and probably remained more frequent since that time . Thirdly, changes in the biological properties of circulating influenza viruses may have occurred, particularly for A(H3N2) subtype —the most dominant virus during the seasons studied.…”

“…Moreover, we did not include cases observed in nursing homes, where elderly could have worse health than those consulting in primary care. Conversely, influenza burden in children could be overestimated relatively to adults’ estimates as children may be more likely to consult a GP than adults . However, consistency of data collection since 1984, using the same ILI definition and epidemic detection method, allowed comparisons over time, as potential bias, if occurred, would be constant in time.…”

“…27 Recently, the 2009 pandemic could have impacted hygiene habits as frequency of hand washing and use of alcohol-based hand sanitizers which were strongly promoted during the epidemic period and probably remained more frequent since that time. 36 Thirdly, changes in the biological properties of circulating influenza viruses may have occurred, particularly for A(H3N2) subtype 37 -the most dominant virus during the seasons studied. The process of antigenic drifts might decrease affinity for human receptors and could affect the efficiency of infection and transmission.…”