Magali Lemaitre

Time lines of infection and disease in human influenza: a review of volunteer challenge studies.

The dynamics of viral shedding and symptoms following influenza virus infection are key factors when considering epidemic control measures. The authors reviewed published studies describing the course of influenza virus infection in placebo-treated and untreated volunteers challenged with wild-type influenza virus. A total of 56 different studies with 1,280 healthy participants were considered. Viral shedding increased sharply between 0.5 and 1 day after challenge and consistently peaked on day 2. The duration of viral shedding averaged over 375 participants was 4.80 days (95% confidence interval: 4.31, 5.29). The frequency of symptomatic infection was 66.9% (95% confidence interval: 58.3, 74.5). Fever was observed in 37.0% of A/H1N1, 40.6% of A/H3N2 (p = 0.86), and 7.5% of B infections (p = 0.001). The total symptoms scores increased on day 1 and peaked on day 3. Systemic symptoms peaked on day 2. No such data exist for children or elderly subjects, but epidemiologic studies suggest that the natural history might differ. The present analysis confirms prior expert opinion on the duration of viral shedding or the frequency of asymptomatic influenza infection, extends prior knowledge on the dynamics of viral shedding and symptoms, and provides original results on the frequency of respiratory symptoms or fever.

Effect of influenza vaccination of nursing home staff on mortality of residents: a cluster-randomized trial.

OBJECTIVES: To evaluate the effect of staff influenza vaccination on all‐cause mortality in nursing home residents.

Comparative age distribution of influenza morbidity and mortality during seasonal influenza epidemics and the 2009 H1N1 pandemic

BackgroundSeveral studies have shown a relatively high mortality rate among young people infected by the 2009 pandemic influenza A (H1N1) virus. Here we compared the age distributions of morbidity and mortality during two seasonal influenza epidemics (H1N1 and H3N2) in France and the United States with those of the 2009 H1N1 pandemic waves in the same countries.MethodsAge-standardized ratios were used to compare the age distribution of morbidity and mortality due to influenza between the two countries and across the different years. Non parametric analysis of variance was used to compare these ratios between epidemic and pandemic influenza.ResultsAge distribution of morbidity was similar between the 2009 pandemic and seasonal epidemics due to H1N1 (p = 0.72) and H3N2 viruses (p = 0.68). In contrast, the proportion of under-60s among influenza deaths was markedly higher during the 2009 pandemic (peak <20 years) than during the seasonal epidemics (respectively p = 0.007 and p = 0.0008).ConclusionsYoung age was a principal mortality risk factor due to the 2009 H1N1 pandemic.

Mortality burden of the 2009 A/H1N1 influenza pandemic in France: comparison to seasonal influenza and the A/H3N2 pandemic.

Background The mortality burden of the 2009 A/H1N1 pandemic remains unclear in many countries due to delays in reporting of death statistics. We estimate the age- and cause-specific excess mortality impact of the pandemic in France, relative to that of other countries and past epidemic and pandemic seasons. Methods We applied Serfling and Poisson excess mortality approaches to model weekly age- and cause-specific mortality rates from June 1969 through May 2010 in France. Indicators of influenza activity, time trends, and seasonal terms were included in the models. We also reviewed the literature for country-specific estimates of 2009 pandemic excess mortality rates to characterize geographical differences in the burden of this pandemic. Results The 2009 A/H1N1 pandemic was associated with 1.0 (95% Confidence Intervals (CI) 0.2–1.9) excess respiratory deaths per 100,000 population in France, compared to rates per 100,000 of 44 (95% CI 43–45) for the A/H3N2 pandemic and 2.9 (95% CI 2.3–3.7) for average inter-pandemic seasons. The 2009 A/H1N1 pandemic had a 10.6-fold higher impact than inter-pandemic seasons in people aged 5–24 years and 3.8-fold lower impact among people over 65 years. Conclusions The 2009 pandemic in France had low mortality impact in most age groups, relative to past influenza seasons, except in school-age children and young adults. The historical A/H3N2 pandemic was associated with much larger mortality impact than the 2009 pandemic, across all age groups and outcomes. Our 2009 pandemic excess mortality estimates for France fall within the range of previous estimates for high-income regions. Based on the analysis of several mortality outcomes and comparison with laboratory-confirmed 2009/H1N1 deaths, we conclude that cardio-respiratory and all-cause mortality lack precision to accurately measure the impact of this pandemic in high-income settings and that use of more specific mortality outcomes is important to obtain reliable age-specific estimates.

Association Between Use of Thiopurines or Tumor Necrosis Factor Antagonists Alone or in Combination and Risk of Lymphoma in Patients With Inflammatory Bowel Disease

Importance An increased risk of lymphoma has been reported among patients receiving thiopurines for inflammatory bowel disease (IBD). The risk of lymphoma associated with anti–tumor necrosis factor (TNF) agents either alone or in combination with thiopurines is uncertain. Objective To assess the risk of lymphoma associated with thiopurines and anti-TNF agents, used alone or in combination, for the management of IBD. Design, Setting, and Participants Nationwide cohort study based on French National Health Insurance databases. Patients aged 18 years or older identified with IBD were included from January 1, 2009, through December 31, 2013, and followed up until December 31, 2015. Exposures At each time of the follow-up, patients were categorized as being exposed to thiopurine monotherapy, anti-TNF monotherapy, or combination therapy, or being unexposed. Main Outcomes and Measures The primary outcome was incident lymphoma. Results Among the 189 289 patients included (54% women; median age, 43 years [interquartile range, 32-56 years]) and followed up for a median of 6.7 years, 123 069 were never exposed during follow-up, 50 405 were exposed to thiopurine monotherapy, 30 294 to anti-TNF monotherapy, and 14 229 to combination therapy. Overall, 336 lymphoma cases occurred: 220 in unexposed patients (incidence rate [IR] per 1000 person-years, 0.26; 95% CI, 0.23-0.29), 70 in patients exposed to thiopurine monotherapy (IR, 0.54; 95% CI, 0.41-0.67), 32 in patients exposed to anti-TNF monotherapy (IR, 0.41; 95% CI, 0.27-0.55), and 14 in patients exposed to combination therapy (IR, 0.95; 95% CI, 0.45-1.45). In a multivariable Cox model, compared with unexposed patients, the risk of lymphoma was higher among those exposed to thiopurine monotherapy (adjusted hazard ratio [aHR], 2.60; 95% CI, 1.96-3.44; P < .001), anti-TNF monotherapy (aHR, 2.41; 95% CI, 1.60-3.64; P < .001), or combination therapy (aHR, 6.11; 95% CI, 3.46-10.8; P < .001). The risk was higher in patients exposed to combination therapy vs those exposed to thiopurine monotherapy (aHR, 2.35; 95% CI, 1.31-4.22; P < .001) or anti-TNF monotherapy (aHR, 2.53; 95% CI, 1.35-4.77; P < .001). Conclusions and Relevance Among adults with IBD, the use of thiopurine monotherapy or anti-TNF monotherapy was associated with a small but statistically significant increased risk of lymphoma compared with exposure to neither medication, and this risk was higher with combination therapy than with each of these treatments used alone. These findings may inform decisions regarding the benefits and risks of treatment.

Surgical Mask to Prevent Influenza Transmission in Households: A Cluster Randomized Trial

Background Facemasks and respirators have been stockpiled during pandemic preparedness. However, data on their effectiveness for limiting transmission are scarce. We evaluated the effectiveness of facemask use by index cases for limiting influenza transmission by large droplets produced during coughing in households. Methodology and Principal Findings A cluster randomized intervention trial was conducted in France during the 2008–2009 influenza season. Households were recruited during a medical visit of a household member with a positive rapid influenza A test and symptoms lasting less than 48 hours. Households were randomized either to the mask or control group for 7 days. In the intervention arm, the index case had to wear a surgical mask from the medical visit and for a period of 5 days. The trial was initially intended to include 372 households but was prematurely interrupted after the inclusion of 105 households (306 contacts) following the advice of an independent steering committee. We used generalized estimating equations to test the association between the intervention and the proportion of household contacts who developed an influenza-like illness during the 7 days following the inclusion. Influenza-like illness was reported in 24/148 (16.2%) of the contacts in the intervention arm and in 25/158 (15.8%) of the contacts in the control arm and the difference between arms was 0.40% (95%CI: −10% to 11%, P = 1.00). We observed a good adherence to the intervention. In various sensitivity analyses, we did not identify any trend in the results suggesting effectiveness of facemasks. Conclusion This study should be interpreted with caution since the lack of statistical power prevents us to draw formal conclusion regarding effectiveness of facemasks in the context of a seasonal epidemic. Trial Registration clinicaltrials.gov NCT00774774

Seasonal H1N1 2007 influenza virus infection is associated with elevated pre-exposure antibody titers to the 2009 pandemic influenza A (H1N1) virus.

The new influenza strain detected in humans in April 2009 has caused the first influenza pandemic of the 21st century. A cross-reactive antibody response, in which antibodies against seasonal H1N1 viruses neutralized the 2009 pandemic influenza A (H1N1) virus (2009 pH1N1), was detected among individuals aged >60 years. However, factors other than age associated with such a cross-reactive antibody response are poorly documented. Our objective was to examine factors potentially associated with elevated pre-exposure viro-neutralization and hemagglutination-inhibition antibody titers against the 2009 pH1N1. We also studied factors associated with antibody titers against the 2007 seasonal H1N1 virus. One hundred subjects participating in an influenza cohort were selected. Sera collected in 2008 were analysed using hemagglutination inhibition and viro-neutralization assays for the 2009 pH1N1 virus and the 2007 seasonal H1N1 virus. Viro-neutralization results were explored using a linear mixed-effect model and hemagglutination-inhibition results using linear-regression models for interval-censored data. Elevated antibody titers against 2009 pH1N1 were associated with seasonal 2007 H1N1 infection (viro-neutralization, p 0.006; hemagglutination-inhibition, p 0.018). Elevated antibody titers were also associated with age in the viro-neutralization assay (p <0.0001). Seasonal 2007 H1N1 infection is an independent predictor of elevated pre-exposure antibody titers against 2009 pH1N1 and may have contributed to lowering the burden of the 2009 pH1N1 pandemic.

Association Between Oral Fluoroquinolone Use and Retinal Detachment.

IMPORTANCE Several studies have focused on the current use of oral fluoroquinolones and the risk for retinal detachment (RD), but the existence of this association is under debate. Given the widespread fluoroquinolone use, investigation of this association is essential. OBJECTIVE To assess the association between oral fluoroquinolone use and the risk for RD, including the rhegmatogenous and exudative types. DESIGN, SETTING, AND PARTICIPANTS This case-crossover study included 27,540 adults with RD from French health care databases from July 1, 2010, through December 31, 2013. Patients with a history of RD or retinal break, endophthalmitis, intravitreal injection, choroidal retinal vitreal biopsy, and human immunodeficiency virus infection or those hospitalized within 6 months of RD were excluded. The risk period of primary interest was current use, defined as exposure to fluoroquinolones within 10 days immediately before RD surgery, according to previous findings. Oral fluoroquinolone use was assumed to start on the day the prescription was dispensed. MAIN OUTCOMES AND MEASURES Exposure to fluoroquinolones during the risk period (1-10 days) compared with the control period (61-180 days). The association was also assessed regarding use in the recent (11-30 days) and past (31-60 days) intermediate risk period, type of fluoroquinolone, and type of RD. RESULTS Of the 27,540 eligible patients (57% men; mean [SD] age, 61.5 [13.6] years), 663 patients with RD were exposed to fluoroquinolones during the observation period, corresponding to 80 cases exposed during the 10-day risk period (≤10 days before RD) and 583 cases exposed during the control period (61-180 days). We found a significant increased risk for RD during the 10-day period after the dispensing of oral fluoroquinolones, with an adjusted odds ratio of 1.46 (95% CI, 1.15-1.87). The risk was significantly increased for rhegmatogenous and exudative RD, with adjusted odds ratios of 1.41 (95% CI, 1.04-1.92) and 2.57 (95% CI, 1.46-4.53), respectively. Recent and past use of fluoroquinolones were not associated with a higher risk for RD, with adjusted odds ratios of 0.94 (95% CI, 0.78-1.14) and 1.06 (95% CI, 0.91-1.24), respectively. CONCLUSIONS AND RELEVANCE Current oral fluoroquinolone use was associated with an increased risk for RD, including the rhegmatogenous and exudative types. These findings, along with the available literature, suggest an association between fluoroquinolone use and the risk for RD. The nature of this association should be further investigated in future studies.

Impact of bucco-dental healthcare on the prevention of pneumonia in geriatrics: a cluster-randomised trial

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Applications of Extreme Value Theory in Public Health.

Objectives We present how Extreme Value Theory (EVT) can be used in public health to predict future extreme events. Methods We applied EVT to weekly rates of Pneumonia and Influenza (P&I) deaths over 1979–2011. We further explored the daily number of emergency department visits in a network of 37 hospitals over 2004–2014. Maxima of grouped consecutive observations were fitted to a generalized extreme value distribution. The distribution was used to estimate the probability of extreme values in specified time periods. Results An annual P&I death rate of 12 per 100,000 (the highest maximum observed) should be exceeded once over the next 30 years and each year, there should be a 3% risk that the P&I death rate will exceed this value. Over the past 10 years, the observed maximum increase in the daily number of visits from the same weekday between two consecutive weeks was 1133. We estimated at 0.37% the probability of exceeding a daily increase of 1000 on each month. Conclusion The EVT method can be applied to various topics in epidemiology thus contributing to public health planning for extreme events.