Whooping cough dynamics in Chile (1932-2010): disease temporal fluctuations across a north-south gradient.

The spatial-temporal dynamics of Bordetella pertussis remains as a highly interesting case in infectious disease epidemiology. Despite large-scale vaccination programs in place for over 50 years around the world, frequent outbreaks are still reported in many countries.
METHODS:
Here, we use annual time series of pertussis incidence from the thirteen different regions of Chile (1952-2010) to study the spatial-temporal dynamics of Pertussis. The period 1975-1995 was characterized by a strong 4 year cycle, while the last two decades of the study period (1990-2010) were characterized by disease resurgence without significant periodic patterns.
RESULTS:
During the first decades, differences in periodic patterns across regions can be explained by the differences in susceptible recruitment. The observed shift in periodicity from the period 1952-1974 to the period 1975-1995 across regions was relatively well predicted by the susceptible recruitment and population size. However, data on vaccination rates was not taken into account in this study.
CONCLUSIONS:
Our findings highlight how demography and population size have interacted with the immunization program in shaping periodicity along a unique latitudinal gradient. Widespread B. pertussis vaccination appears to lead to longer periodic dynamics, which is line with a reduction in B. pertussis transmission, but our findings indicate that regions characterized by both low birth rate and population size decreased in periodicity following immunization efforts

Authors:Lima M1,2, Estay SA3,4, Fuentes R5, Rubilar P6, Broutin H7, Chowell-Puente G8.
Journal:BMC Infect Dis. 2015
Link:http://www.ncbi.nlm.nih.gov/pubmed/26714644