Effect of the 2009 influenza A(H1N1) pandemic on invasive pneumococcal pneumonia

J Infect Dis. 2013 Apr;207(7):1135-43. doi: 10.1093/infdis/jit008. Epub 2013 Jan 9.

Abstract

Background: Because pneumococcal pneumonia was prevalent during previous influenza pandemics, we evaluated invasive pneumococcal pneumonia (IPP) rates during the 2009 influenza A(H1N1) pandemic.

Methods: We identified laboratory-confirmed, influenza-associated hospitalizations and IPP cases (pneumococcus isolated from normally sterile sites with discharge diagnoses of pneumonia) using active, population-based surveillance in the United States. We compared IPP rates during peak pandemic months (April 2009-March 2010) to mean IPP rates in nonpandemic years (April 2004-March 2009) and, using Poisson models, to 2006-2008 influenza seasons.

Results: Higher IPP rates occurred during the peak pandemic month compared to nonpandemic periods in 5-24 (IPP rate per 10 million: 48 vs 9 (95% confidence interval [CI], 5-13), 25-49 (74 vs 53 [CI, 41-65]), 50-64 (188 vs 114 [CI, 85-143]), and ≥65-year-olds (229 vs 187 [CI, 159-216]). In the models with seasonal influenza rates included, observed IPP rates during the pandemic peak were within the predicted 95% CIs, suggesting this increase was not greater than observed with seasonal influenza.

Conclusions: The recent influenza pandemic likely resulted in an out-of-season IPP peak among persons ≥5 years. The IPP peak's magnitude was similar to that seen during seasonal influenza epidemics.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Child, Preschool
  • Confidence Intervals
  • Databases, Factual
  • Female
  • Hospitalization
  • Humans
  • Influenza A Virus, H1N1 Subtype / pathogenicity*
  • Influenza, Human / epidemiology*
  • Influenza, Human / microbiology
  • Male
  • Middle Aged
  • Odds Ratio
  • Pandemics*
  • Pneumonia, Pneumococcal / epidemiology*
  • Pneumonia, Pneumococcal / virology
  • Poisson Distribution
  • Population Surveillance
  • Risk Factors
  • Seasons
  • Severity of Illness Index
  • Streptococcus pneumoniae / isolation & purification
  • Streptococcus pneumoniae / pathogenicity
  • United States / epidemiology
  • Young Adult