Influenza increases invasive meningococcal disease risk in temperate countries

Area of Science:

• Epidemiology
• Infectious Diseases
• Public Health

Background:

• Invasive meningococcal disease (IMD) exhibits winter seasonality in temperate climates.
• The precise drivers of IMD seasonality, including environmental factors and respiratory virus co-infections, remain unclear.
• Understanding these drivers is crucial for effective public health interventions.

Purpose of the Study:

• To investigate the independent contributions of influenza virus activity and environmental conditions to the risk of IMD.
• To assess the consistency of these associations across multiple international jurisdictions.

Main Methods:

• A case-crossover study design was employed, analyzing 3276 IMD cases from 1999-2011 across Australia, Canada, France, and the United States.
• Standardized methodology was used to evaluate the impact of normalized weekly influenza activity and environmental exposures on IMD risk.
• Meta-analytic techniques were applied to assess the homogeneity of effects and identify sources of heterogeneity between regions.

Main Results:

• Elevated influenza activity, with a 2-week lag, was significantly associated with an increased risk of IMD (aOR 1.29, 95% CI 1.04-1.59), an effect consistent across all studied regions.
• No environmental exposures demonstrated a generalizable association with IMD risk across the evaluated jurisdictions.
• The observed association between influenza and IMD remained significant after adjusting for environmental factors.

Conclusions:

• Surges in influenza activity acutely increase population-level risk for invasive meningococcal disease.
• This influenza-driven increase in IMD risk is observable across diverse geographic regions, including North America, France, and Australia.
• The impact of influenza on subsequent meningococcal disease risk suggests a potential, indirect benefit of influenza immunization programs.