Seasonal patterns of invasive pneumococcal disease.

Scott F Dowell,Charles E Rose,Carolyn Wright,Cynthia G Whitney,Anne Schuchat

doi:10.3201/eid0905.020556

Scott F Dowell, Charles E Rose + Show 3 more

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https://doi.org/10.3201/eid0905.020556

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Abstract

Pneumococcal infections increase each winter, a phenomenon that has not been well explained. We conducted population-based active surveillance for all cases of invasive pneumococcal disease in seven states; plotted annualized weekly rates by geographic location, age, and latitude; and assessed correlations by time-series analysis. In all geographic areas, invasive pneumococcal disease exhibited a distinct winter seasonality, including an increase among children in the fall preceding that for adults and a sharp spike in incidence among adults each year between December 24 and January 7. Pneumococcal disease correlated inversely with temperature (r –0.82 with a 1-week lag; p<0.0001), but paradoxically the coldest states had the lowest rates, and no threshold temperature could be identified. The pattern of disease correlated directly with the sinusoidal variations in photoperiod (r +0.85 with a 5-week lag; p<0.0001). Seemingly unrelated seasonal phenomena were also somewhat correlated. The reproducible seasonal patterns in varied geographic locations are consistent with the hypothesis that nationwide seasonal changes such as photoperiod-dependent variation in host susceptibility may underlie pneumococcal seasonality, but caution is indicated in assigning causality as a result of such correlations.

Highlights

Pneumococcal infections increase each winter, a phenomenon that has not been well explained
The seasonal variation has been more apparent in adult invasive pneumococcal disease than in pediatric cases [1], some seasonal variation in acquisition of nasopharyngeal colonization has been documented in children [6]
No seasonal variation was seen in the incidence of group B streptococcal infection, and a mild spring peak was seen in group A streptococcal infection

Summary

Introduction

Pneumococcal infections increase each winter, a phenomenon that has not been well explained. We conducted population-based active surveillance for all cases of invasive pneumococcal disease in seven states; plotted annualized weekly rates by geographic location, age, and latitude; and assessed correlations by time-series analysis. Invasive pneumococcal disease exhibited a distinct winter seasonality, including an increase among children in the fall preceding that for adults and a sharp spike in incidence among adults each year between December 24 and January 7. We evaluated data from a population-based surveillance system in seven geographic areas in the United States (Active Bacterial Core Surveillance) to describe the seasonal variation in invasive pneumococcal disease and explore these hypotheses. As with many infectious diseases, the incidence of invasive pneumococcal infection rises and falls in an annual seasonal pattern that has been repeatedly documented but never well explained.

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