Modelling pertussis seasonality

PAULA BERGERO; PABLO SEBASTIÁN PESCO

Trieste

Workshop; Workshop on Mathematical Models of Climate Variability, Environmental Change, and Infectious Diseases; 2013

ICTP, International Center for Theoretical Physics

Seasonal change in the incidence of infectious diseases is a common phenomenon, but the mechanisms responsible for seasonal behaviour, and the epidemiological consequences of seasonality, are poorly understood. In particular, Pertussis seasonal pattern, has been reported in different seasons (summer and fall in USA, August in Neherlands, except for 13-18 years age group where the peak occurred in November, Winter in Argentina) Explanations can be grouped in 3 types: changes in the behaviour of the host (globall changes in contact patterns), changes in atmospheric conditionsor changes in prevalence or virulence of pathogens(appareance/disappareance)?. No single theory has provide satisfactory explanations about the causes. In this work, we focus in 2 first possibilities, this is: Could contact patterns changes explain it? Is any climatic variable playing a role? As conclusions of this preliminar work, we show that changes in contact patterns included in a SEIR-gamma model as school-term only does not seem to be significant for seasonal behavior. By the other side,including a forcing term in the SEIR-gamma model through Latent Heat Flux (LHF) variation, the annual observed peak can be reproduced (the 4 years intrinsic period is also sustained) and agree with epidemiological data form Córdoba, Argentina. The LHF could be then the climate variable that modulates the wintertime pertussis through an increase in the transmission of the disease. Our work suggest that experimental work is suggested to test this possibility.