Abstract
BackgroundData from prospectively planned cohort studies on risk of major clinical outcomes and prognostic factors for patients with influenza A(H1N1)pdm09 virus are limited. In 2009, in order to assess outcomes and evaluate risk factors for progression of illness, two cohort studies were initiated: FLU 002 in outpatients and FLU 003 in hospitalized patients.Methods and FindingsBetween October 2009 and December 2012, adults with influenza-like illness (ILI) were enrolled; outpatients were followed for 14 days and inpatients for 60 days. Disease progression was defined as hospitalization and/or death for outpatients, and hospitalization for >28 days, transfer to intensive care unit (ICU) if enrolled from general ward, and/or death for inpatients. Infection was confirmed by RT-PCR. 590 FLU 002 and 392 FLU 003 patients with influenza A (H1N1)pdm09 were enrolled from 81 sites in 17 countries at 2 days (IQR 1–3) and 6 days (IQR 4–10) following ILI onset, respectively. Disease progression was experienced by 29 (1 death) outpatients (5.1%; 95% CI: 3.4–7.2%) and 80 inpatients [death (32), hospitalization >28 days (43) or ICU transfer (20)] (21.6%; 95% CI: 17.5–26.2%). Disease progression (death) for hospitalized patients was 53.1% (26.6%) and 12.8% (3.8%), respectively, for those enrolled in the ICU and general ward. In pooled analyses for both studies, predictors of disease progression were age, longer duration of symptoms at enrollment and immunosuppression. Patients hospitalized during the pandemic period had a poorer prognosis than in subsequent seasons.ConclusionsPatients with influenza A(H1N1)pdm09, particularly when requiring hospital admission, are at high risk for disease progression, especially if they are older, immunodeficient, or admitted late in infection. These data reinforce the need for international trials of novel treatment strategies for influenza infection and serve as a reminder of the need to monitor the severity of seasonal and pandemic influenza epidemics globally.Trial RegistrationClinicalTrials.gov Identifiers: FLU 002- NCT01056354, FLU 003- NCT01056185.
Highlights
The emergence of influenza A(H1N1)pdm09 virus in 2009 highlighted the importance of having infrastructures in place to conduct research that would inform patient management on emerging viruses [1]
Patients with influenza A(H1N1)pdm09, when requiring hospital admission, are at high risk for disease progression, especially if they are older, immunodeficient, or admitted late in infection. These data reinforce the need for international trials of novel treatment strategies for influenza infection and serve as a reminder of the need to monitor the severity of seasonal and pandemic influenza epidemics globally
Between October 2009 and December 2012, 2,602 patients were enrolled as outpatients in FLU 002, among whom 590 (23%) had laboratory-confirmed A(H1N1)pdm09 virus infection (Figure 1)
Summary
The emergence of influenza A(H1N1)pdm virus in 2009 highlighted the importance of having infrastructures in place to conduct research that would inform patient management on emerging viruses [1]. Clinical data close to the time of diagnosis are needed to study risk factors for progression. Such data would be available from geographically diverse settings over several influenza seasons with different influenza viruses in order to understand changing patterns of disease and risk factors of progression. These data could inform clinical management strategies as well as the design of intervention studies. Data from prospectively planned cohort studies on risk of major clinical outcomes and prognostic factors for patients with influenza A(H1N1)pdm virus are limited. In 2009, in order to assess outcomes and evaluate risk factors for progression of illness, two cohort studies were initiated: FLU in outpatients and FLU in hospitalized patients
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