Abstract
Rotavirus is a major cause of mortality in developing countries, and yet the dynamics of rotavirus in such settings are poorly understood. Rotavirus is typically less seasonal in the tropics, although recent observational studies have challenged the universality of this pattern. While numerous studies have examined the association between environmental factors and rotavirus incidence, here we explore the role of intrinsic factors. By fitting a mathematical model of rotavirus transmission dynamics to published age distributions of cases from 15 countries, we obtain estimates of local transmission rates. Model-predicted patterns of seasonal incidence based solely on differences in birth rates and transmission rates are significantly correlated with those observed (Spearman's ρ = 0.65, p < 0.05). We then examine seasonal patterns of rotavirus predicted across a range of different birth rates and transmission rates and explore how vaccination may impact these patterns. Our results suggest that the relative lack of rotavirus seasonality observed in many tropical countries may be due to the high birth rates and transmission rates typical of developing countries rather than being driven primarily by environmental conditions. While vaccination is expected to decrease the overall burden of disease, it may increase the degree of seasonal variation in the incidence of rotavirus in some settings.
Highlights
Rotavirus is one of the leading causes of severe diarrhoea in children in both developed and developing countries, and is estimated to cause over half a million deaths worldwide with much of this mortality burden concentrated in developing countries [1,2]
Determining how the potential impact of vaccination may vary between developed versus developing countries requires an understanding of how the transmission dynamics of rotavirus differ in these settings
Birth rates have been shown to be an important determinant of the spatio-temporal pattern of rotavirus epidemics in the USA [13], and may help explain why rotavirus tends to be less seasonal in developing countries, which often exhibit high birth rates and high transmission rates
Summary
Rotavirus is one of the leading causes of severe diarrhoea in children in both developed and developing countries, and is estimated to cause over half a million deaths worldwide with much of this mortality burden concentrated in developing countries [1,2]. Observations of vaccine impact in the USA, Australia and several countries in Latin America and Europe have highlighted the enormous promise such vaccines hold for preventing rotavirus-associated diarrhoea [3]. Clinical trials have estimated that vaccine recipients benefit from a 49– 98% reduction in the risk of severe rotavirus diarrhoea depending on the setting, with lower efficacy being observed in low-income regions of Africa and Asia [4 –10]. This can be achieved through mathematical modelling studies rooted in biological and epidemiological data [11,12,13,14,15,16]
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