Pertussis (whooping cough) manifests most severely in children less than one year old, especially in prevaccine-age infants (<6 months old). Because of the low social connectivity in this age group, other more mobile/social age groups act as important vectors for disease transmission. Applying spatial analytical methods to a 19-year Massachusetts pertussis data set with zip code level spatial information, we seek to 1) identify the age group(s) involved in disease transmission to prevaccine-age infants, 2) identify partially separate chains-of- transmission in different age groups by analyzing synchrony and phase coherence among different groups, 3) reassess factors affecting local dynamics for each population and 4) investigate the presented local spatial hotspots.
Results/Conclusions
We find that prevaccine-age infants are in phase with adults, but not teenagers during the year. The bulk of prevaccine-age infant cases occur during the warmer months and teenage cases during the colder months, whereas adult cases overlaps with both time periods. The epidemic peaks of the total population appear to be driven by teenage cases. We further examined patterns and epidemic drivers in time and space, and the asynchrony in dynamics testifies to a surprising degree of age structure in the local chains of transmission.
