Excess cases of Influenza like illnesses in France synchronous with COVID19 invasion

Boëlle, Pierre‐Yves

doi:10.1101/2020.03.14.20035741

Cited by 3 publications

(6 citation statements)

References 6 publications

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“…Recent ILI data for the United States show a markedly lower epidemic peak for the 2019-2020 influenza season compared to what would be expected based on the pre-holiday peak [8]. A similar phenomenon has been observed in other locations including Hong Kong and France [9,10]. Understanding this uncharacteristic ILI behavior is important for understanding influenza epidemiology and optimizing influenza mitigation e↵orts.…”

Section: Introductionmentioning

confidence: 80%

“…To understand the impacts of COVID-19 on influenza, we first look retrospectively. By the time SARS-CoV-2 transmission had become widespread in early 2020, the influenza season in Europe was largely over (Boelle, 2020), but flu transmission in the US was still ongoing and declined rapidly in March and April (CDC, 2020a). Some have proposed that the pandemic and the ensuing nonpharmaceutical interventions led to this unexpected decrease in influenza transmission (Olsen et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Double trouble? When a pandemic and seasonal virus collide

Zipfel

Bansal

2020

Preprint

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The 2019-2020 influenza sentinel surveillance data exhibits unexpected trends. Typical influenza seasons have a small herald wave, followed by a decrease due to school closure during holidays, and then a main post-holiday peak that is significantly larger than the pre-holiday wave. During the 2019-2020 influenza season, influenza-like illness data in the United States appears to have a markedly lower main epidemic peak compared to what would be expected based on the pre-holiday peak. We hypothesize that the 2019-2020 influenza season does have a lower than expected burden and that this deflation is due to a behavioral or ecological interaction with COVID-19. We apply an intervention analysis to assess if this influenza season deviates from expectations, then we compare multiple hypothesized drivers of the decrease in influenza in a spatiotemporal regression model. Lastly, we develop a mechanistic metapopulation model, incorporating transmission reduction that scales with COVID-19 risk perception. We find that the 2019-2020 ILI season is smaller and decreases earlier than expected based on prior influenza seasons, and that the increase in COVID-19 risk perception is associated with this decrease. Additionally, we find that a 5% average reduction in transmission is su cient to reproduce the observed flu dynamics. We propose that precautionary behaviors driven by COVID-19 risk perception or increased isolation driven by undetected COVID-19 spread dampened the influenza season. We suggest that when surveillance for a novel pathogen is limited, surveillance streams of co-circulating infections may provide a signal.

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Section: Introductionmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Double trouble? When a pandemic and seasonal virus collide

Zipfel

Bansal

2020

Preprint

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“…Some have thus speculated that undetected COVID-19 cases may have been categorised as influenza before the first official case was reported in Spain. 13 …”

Section: Introductionmentioning

confidence: 99%

“…Some have thus speculated that undetected COVID-19 cases may have been categorised as influenza before the first official case was reported in Spain. 13 Catalonia is fortunate to have a reliable system for influenza surveillance in place. A network of 60 sentinel general practitioners (GPs) covering 1% of the total population report daily cases of influenza-like illness (ILI) and take samples for differential diagnosis and confirmation of influenza infections in the region.…”

mentioning

confidence: 99%

Excess cases of influenza and the coronavirus epidemic in Catalonia: a time-series analysis of primary-care electronic medical records covering over 6 million people

et al. 2020

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ObjectivesThere is uncertainty about when the first cases of COVID-19 appeared in Spain. We aimed to determine whether influenza diagnoses masked early COVID-19 cases and estimate numbers of undetected COVID-19 cases.DesignTime-series study of influenza and COVID-19 cases, 2010–2020.SettingPrimary care, Catalonia, Spain.ParticipantsPeople registered in primary-care practices, covering >6 million people and >85% of the population.Main outcome measuresWeekly new cases of influenza and COVID-19 clinically diagnosed in primary care.AnalysesDaily counts of both cases were computed using the total cases recorded over the previous 7 days to avoid weekly effects. Epidemic curves were characterised for the 2010–2011 to 2019–2020 influenza seasons. Influenza seasons with a similar epidemic curve and peak case number as the 2019–2020 season were used to model expected case numbers with Auto Regressive Integrated Moving Average models, overall and stratified by age. Daily excess influenza cases were defined as the number of observed minus expected cases.ResultsFour influenza season curves (2011–2012, 2012–2013, 2013–2014 and 2016–2017) were used to estimate the number of expected cases of influenza in 2019–2020. Between 4 February 2020 and 20 March 2020, 8017 (95% CI: 1841 to 14 718) excess influenza cases were identified. This excess was highest in the 15–64 age group.ConclusionsCOVID-19 cases may have been present in the Catalan population when the first imported case was reported on 25 February 2020. COVID-19 carriers may have been misclassified as influenza diagnoses in primary care, boosting community transmission before public health measures were taken. The use of clinical codes could misrepresent the true occurrence of the disease. Serological or PCR testing should be used to confirm these findings. In future, this surveillance of excess influenza could help detect new outbreaks of COVID-19 or other influenza-like pathogens, to initiate early public health responses.

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“…Some have thus speculated that undetected COVID-19 cases may have been categorised as influenza before the first official case was reported in Spain. [9] Catalonia is fortunate to have a reliable system for influenza surveillance in place. A network of 60 sentinel general practitioners covering 1% of the total population report daily cases of influenza-like illness (ILI) and take samples for differential diagnosis and confirmation of influenza infections in the region.…”

Section: Introductionmentioning

confidence: 99%

Excess cases of influenza suggest an earlier start to the coronavirus epidemic in Spain than official figures tell us: an analysis of primary care electronic medical records from over 6 million people from Catalonia

Coma

Mora

Prats‐Uribe

et al. 2020

Preprint

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Objectives:There is uncertainty about when the first cases of COVID-19 appeared in Spain, as asymptomatic patients can transmit the virus. We aimed to determine whether influenza diagnoses masked early COVID-19 cases and, if so, estimate numbers of undetected COVID-19 cases in a large database of primary-care records covering >6 million people in Catalonia. Design: Time-series study of influenza and COVID-19 cases, using all influenza seasons from autumn-winter 2010-2011 to autumn-winter 2019-2020. Setting: Primary care, Catalonia, Spain. Participants: People registered in one of the contributing primary-care practices, covering >6 million people and >85% of the population. Main outcome measures: Weekly new cases of influenza and COVID-19 diagnosed in primary care. Analyses: Daily counts of both cases were computed using the total cases recorded over the previous 7 days to avoid weekly effects on recording practice. Epidemic curves were characterised for the 2010-2011 to 2019-2020 influenza seasons. Influenza seasons with a similar epidemic curve and peak case number as the 2019-2020 season were used to model predictions for 2019-2020. ARIMA models were fitted to the included influenza seasons, overall and stratified by age, to estimate expected case numbers. Daily excess influenza cases were defined as the number of observed minus expected cases. Results: Four influenza season curves (

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Excess cases of Influenza like illnesses in France synchronous with COVID19 invasion

Cited by 3 publications

References 6 publications

Double trouble? When a pandemic and seasonal virus collide

Double trouble? When a pandemic and seasonal virus collide

Excess cases of influenza and the coronavirus epidemic in Catalonia: a time-series analysis of primary-care electronic medical records covering over 6 million people

Excess cases of influenza suggest an earlier start to the coronavirus epidemic in Spain than official figures tell us: an analysis of primary care electronic medical records from over 6 million people from Catalonia

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