HealthDay News — Population density and structure may impact the length of the influenza season regardless of climatic conditions, according to a study published in the Oct. 5 issue of Science.

Benjamin D. Dalziel, PhD, from Oregon State University in Corvallis, and colleagues examined the impact of population size and structure on influenza incidence among cities. Weekly incidence data were examined from 603 US regions of varying size and with varying structures, including transportation patterns.

The researchers found that epidemics in smaller cities were focused on a shorter period of the influenza season, while the incidence was more diffuse in larger cities. Using city-level incidence data, base transmission potential was positively correlated with population size and with spatiotemporal organization in population density in the presence of climate forcing. In urban centers, increased base transmission potential enhanced influenza spread outside of peak season, elevating herd immunity to currently circulating strains and thereby reducing the explosive spread when climatic conditions were most favorable for transmission; consequently, larger cities with higher base transmission potentials have more diffuse influenza epidemics.

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“As the growth and form of cities affect their function as climate-driven incubators of infectious disease, it may be possible to design smarter cities that better control epidemics in the face of accelerating global change,” the authors write.

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