Populations at Risk for Severe or Complicated Avian Influenza H5N1: A Systematic Review and Meta-Analysis

Abstract

BackgroundLittle is known about risk factors for severe outcomes in patients infected with H5N1 and no systematic review has been conducted. Understanding risk factors is an important step for prioritizing prophylaxis or treatment in the event of a pandemic.ObjectivesTo systematically evaluate risk factors for severe outcomes in patients with avian influenza H5N1 infection.Data sourcesMEDLINE, EMBASE, CINAHL, GlobalHealth, and CENTRAL through March 2011Eligibility criteria for selecting studiesObservational studies of any design published in English, French, Spanish, German or Korean that reported on risk factor-outcome combinations of interest in participants with confirmed H5N1 infections. Outcomes considered included death, ventilator support, hospital and ICU admission, pneumonia, and composite outcomes.Study appraisalRisk of bias was assessed using the Newcastle-Ottawa scale (NOS).ResultsWe identified 20 studies reporting on 999 patients infected with H5N1. The majority of studies (n = 14, 70%) were at intermediate risk of bias, i.e. 4–6 points on the NOS. Females were at increased risk of death (OR 1.75, 95% CI 1.27–2.44), while young age, in particular <5 years of age (OR 0.44, 95% CI 0.25–0.79 for death), was protective. Data on traditional risk factors was scarce and requires further studies. Another major limitation in the published literature was lack of adjustment for confounders.InterpretationFemales were at increased risk for complications following H5N1 infection while young age protected against severe outcomes. Research on traditional risk factors was limited and is required.

Emerging respiratory tract viral infections

“…Delay in the delivery of appropriate treatment to patients with influenza A(H5N1) infection in Indonesia was mainly related to delay in diagnosis rather than late presentation to healthcare settings [16]. A systematic review has shown that women were at a higher risk of death [odds ratio (OR) 1.75, 95% confidence interval (95% CI) 1.27-2.44] following A(H5N1) infection, whereas young age, in particular less than 5 years old, was protective (OR 0.44, 95% CI 0.25-0.79) [18]. A systematic review has shown that women were at a higher risk of death [odds ratio (OR) 1.75, 95% confidence interval (95% CI) 1.27-2.44] following A(H5N1) infection, whereas young age, in particular less than 5 years old, was protective (OR 0.44, 95% CI 0.25-0.79) [18].…”

Underweight, overweight, and obesity as independent risk factors for hospitalization in adults and children from influenza and other respiratory viruses

“…While there was no increase in the rates of ILI being reported in obese patients, early reports during the pandemic noted an association between severity of illness and obesity . Several studies in adults found an association between obesity and death due to pandemic influenza . Another study, however, found no association between obesity and mortality in intensive care unit (ICU) participants …”

A clinical approach to the threat of emerging influenza viruses in the Asia‐Pacific region

“…25 A systematic review has shown that females were at higher risk of death (OR: 1.75, 95% CI: 1.27-2.44) following A(H5N1) infection, whereas young age in particular <5 years was protective (OR: 0.44, 95% CI: 0.25-0.79). 26…”