Data from: Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics

More than a century of ecological studies have demonstrated the importance
of demography in shaping spatial and temporal variation in population
dynamics. Surprisingly, the impact of seasonal recruitment on infectious
disease systems has received much less attention. Here, we present data
encompassing 78 years of monthly natality in the USA, and reveal
pronounced seasonality in birth rates, with geographical and temporal
variation in both the peak birth timing and amplitude. The timing of
annual birth pulses followed a latitudinal gradient, with northern states
exhibiting spring/summer peaks and southern states exhibiting autumn
peaks, a pattern we also observed throughout the Northern Hemisphere.
Additionally, the amplitude of United States birth seasonality was more
than twofold greater in southern states versus those in the north. Next,
we examined the dynamical impact of birth seasonality on childhood disease
incidence, using a mechanistic model of measles. Birth seasonality was
found to have the potential to alter the magnitude and periodicity of
epidemics, with the effect dependent on both birth peak timing and
amplitude. In a simulation study, we fitted an
susceptible-exposed-infected-recovered model to simulated data, and
demonstrated that ignoring birth seasonality can bias the estimation of
critical epidemiological parameters. Finally, we carried out statistical
inference using historical measles incidence data from New York City. Our
analyses did not identify the predicted systematic biases in parameter
estimates. This may be owing to the well-known frequency-locking between
measles epidemics and seasonal transmission rates, or may arise from
substantial uncertainty in multiple model parameters and estimation
stochasticity.