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

Abstract

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-infectedrecovered 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.

Quantifying seasonal population fluxes driving rubella transmission dynamics using mobile phone data

“…As has been found in high-income settings, but in contrast to other African countries, rubella transmission was strongly positively related to school term times (t test, t = −3.6681, df = 80.505, P < 1e-3 for provinces excluding the Northeastern province where power for analysis was weak); transmission was not significantly correlated with rainfall (mean correlation coefficient, −0.13; 95% quantile interval, −0.34, 0.07, P > 0.2, excluding the Northeastern province; Fig. S3 and Table S1) (1,13,27,28). There was also a strong positive relationship with province-level population flux in the previous month normalized for each province (mean correlation coefficient, 0.38; 95% quantile interval, 0.18, 0.55, P < 1e-3, excluding the Northeastern province).…”

Host and pathogen ecology drive the seasonal dynamics of a fungal disease, white-nose syndrome

“…Mating frequently increases infectious contacts, whereas territoriality can decrease contact rates among hosts [2,5,13]. Second, seasonal birth pulses can increase transmission by creating an influx of susceptible individuals into an otherwise mostly immune population [14][15][16]. Third, seasonal changes in host habitat use can influence the transmission and persistence of pathogens by altering contact with infective stages in the environment [17,18].…”

Seasonality in Smoking Behaviour: Re-Evaluating the Effects of the 2005 Public Smoking Ban in Italy

“…More generally, similar issues could arise in all studies where the outcome of interest exhibits seasonal variation, as for alcohol consumption (Uitenbroek 1996;Cho et al 2001), mental health issues (Huibers et al 2010;Ayers et al 2013) or fertility (Buckles and Hungerman 2013;Martinez-Bakker et al 2014). …”