Impact of Birth Seasonality on Dynamics of Acute Immunizing Infections in Sub-Saharan Africa

Audrey Dorelien, University of Michigan

We analyze the impact of birth seasonality on the dynamics of childhood infectious diseases. We find that birth seasonality can induce either annual or biennial epidemics. Changes in the magnitude of the birth fluctuations (birth amplitude) can induce significant changes in the size of the epidemic peaks. Changes in the magnitude of birth amplitude have little impact on timing of disease epidemic within the year. In contrast, changes to the birth seasonality phase (location of the peak in birth amplitude within the year) significantly influence the timing of the epidemics. In the presence of seasonality in contact rates, at relatively low birth rates (20 per 1000), birth amplitude has little impact on the dynamics but does have an impact on the magnitude and timing of the epidemics. However, as the mean birth rate increases, both birth amplitude and phase play an important role in driving the dynamics of the epidemic.