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We described bronchiolitis epidemics during the 2020-2021 and 2021-2022 seasons in France and their interaction with the COVID outbreak.Data on family physician (FP) visits, emergency department (ED) visits, hospitalizations for bronchiolitis for children˂2 years, and hospital virological data were analyzed and compared with previous seasons (2015-2020).The 2020-2021 epidemic arrived very late, and its impact was lower than in previous seasons (2015-2020) (FP visits: -23%, ED visits: -38%, and hospitalizations: -30%). The 2021-2022 epidemic started early (week 40) and lasted for a relatively long time (13 weeks). The impact was higher than in 2015-2020 (FP visits: +13%, ED visits: +34%, hospitalizations: +28%).Findings from the 2020-2021 epidemic may be linked to the implementation of non-pharmaceutical COVID-19 prevention measures. For 2021-2022, findings may be linked to an "immunity debt" resulting from the lower impact of the previous season.

Background Interventions to mitigate the COVID-19 pandemic may impact other respiratory diseases. Aims We aimed to study the course of pertussis in France over an 8-year period including the beginning of the COVID-19 pandemic and its association with COVID-19 mitigation strategies, using multiple nationwide data sources and regression models. Methods We analysed the number of French pertussis cases between 2013 and 2020, using PCR test results from nationwide outpatient laboratories (Source 1) and a network of the paediatric wards from 41 hospitals (Source 2). We also used reports of a national primary care paediatric network (Source 3). We conducted a quasi-experimental interrupted time series analysis, relying on negative binomial regression models. The models accounted for seasonality, long-term cycles and secular trend, and included a binary variable for the first national lockdown (start 16 March 2020). Results We identified 19,039 pertussis cases from these data sources. Pertussis cases decreased significantly following the implementation of mitigation measures, with adjusted incidence rate ratios of 0.10 (95% CI: 0.04–0.26) and 0.22 (95% CI: 0.07–0.66) for Source 1 and Source 2, respectively. The association was confirmed in Source 3 with a median of, respectively, one (IQR: 0–2) and 0 cases (IQR: 0–0) per month before and after lockdown (p = 0.0048). Conclusions The strong reduction in outpatient and hospitalised pertussis cases suggests an impact of COVID-19 mitigation measures on pertussis epidemiology. Pertussis vaccination recommendations should be followed carefully, and disease monitoring should be continued to detect any resurgence after relaxation of mitigation measures.

BackgroundInterventions to mitigate coronavirus disease 19 (COVID-19) pandemic may impact other respiratory diseases such as pertussis. We aimed to study the course of pertussis in France over an 8-year period and its association with COVID-19 mitigation strategies, using multiple nationwide data sources.MethodsWe analyzed the number of French pertussis cases between 2013 and 2020, using the PCR test results from nationwide outpatient laboratories (Source 1) and the pediatric network of 41 hospitals (Source 2), and using the reports of an office-based pediatric national network (Source 3). We conducted a quasi-experimental interrupted time-series analysis, relying on negative binomial regression models. The models accounted for seasonality, long-term cycles, and secular trend, and included a binary variable for the first national lockdown (ordered on March 16, 2021).ResultsWe identified 19,039 cases of pertussis from the three data sources during the study period. There was a significant decrease of pertussis cases following the implementation of mitigation measures, with adjusted incidence rate ratios of 0.102 (95% CI 0.040-0.256) and 0.216 (95% CI 0.071-0.656) for Source 1 and Source 2, respectively. The association was confirmed in Source 3 (median of 1 [IQR 0-2] vs. 0 [IQR 0-0] pertussis cases per month before and after lockdown, respectively, p=0.0048).ConclusionThe drastic reduction of outpatient and hospitalized cases of pertussis strongly suggests an impact of COVID-19 mitigation measures and their consequences on pertussis epidemiology. Pertussis vaccination recommendations should be carefully followed, and disease monitoring should be continued to detect any resurgence after relaxation of mitigation measures.FundingThere was no specific funding for the study.

International audience; BACKGROUND:Neisseria meningitidis group W (NmW) belonging to the clonal complex ST-11 (NmW/cc11) spread in Europe and in France in 2000 and declined thereafter. In France, invasive meningococcal disease (IMD) due to NmW increased again in 2012 and thereafter since 2015. Several sub-lineages of NmW/cc11 are circulating worldwide with successive epidemic waves. We aimed to describe recent epidemiological trends of NmW in France and to explore the microbiological and epidemiological characteristics associated with different NmW/cc11 sub-lineages.METHODS:The epidemiology of NmW was described based on data collected through mandatory notification of IMD and strain typing data for culture-confirmed and PCR-confirmed cases for the period 2000-2016. All culture-confirmed cases due to NmW from the period 2010-2016 were characterised by whole genome sequencing (WGS). A detailed epidemiological analysis was performed for culture-confirmed cases on the basis of WGS data.FINDINGS:During the period 2010-2016, genotyping was obtained for 148 cases including all the 132 culture-confirmed cases, among which 127 were matched with epidemiological data, and 16 PCR-confirmed cases (out of a total of 47 PCR-confirmed cases). An increase in IMD was observed in 2012 and was linked to isolates belonging to the "Anglo-French-Hajj" sub-lineage. These isolates have decreased significantly since 2013 and have been replaced by NmW/cc11 isolates related to the "South American - UK" sub-lineage which caused a marked increase in the number of cases of NmW in 2016. In this sub-lineage, the "original UK strain" was first detected in 2012 and increased thereafter, followed by the recently described "UK 2013-strain". Isolates related to the "South American-UK" sub-lineage represented 45% of all NmW cultured isolates from the whole period 2010-2016 but were the most frequent isolates in 2016, representing 76% of the total NmW typed isolates and 94% of the typed NmW/cc11 isolates. A changing pattern in the epidemiology of NmW has been observed in 2015-2016 in relation to the spread of the "UK 2013-strain" with a sharp increase in the number of cases among persons aged 15 years and over and a high case fatality rate (CFR). Among cases due to the "UK 2013-strain", 94% of cases were aged 15 years and over and the CFR was 28%.INTERPRETATION:Our data suggest a recent clonal replacement among NmW/cc11 isolates with the expansion of the "South American-UK" sub-lineage in France and particularly the "UK 2013-strain" which was predominant in 2015 and 2016. A shift in the age-distribution of IMD due to NmW to older ages and the high CFR are consistent with the expansion of a new virulent clone in a naive population. These data may have an impact on tailoring vaccination strategies against NmW.