Park Sang Woo, Holmdahl Inga, Howerton Emily, Yang Wenchang, Baker Rachel E, Vecchi Gabriel A, Cobey Sarah, Metcalf C Jessica E, Grenfell Bryan T
Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
medRxiv. 2025 Mar 3:2025.03.02.25323095. doi: 10.1101/2025.03.02.25323095.
Titrating the relative importance of endogenous and exogenous drivers for dynamical transitions in host-pathogen systems remains an important research frontier towards predicting future outbreaks and making public health decisions. In Japan, respiratory syncytial virus (RSV), a major childhood respiratory pathogen, displayed a sudden, dramatic shift in outbreak seasonality (from winter to fall) in 2016. This shift was not observed in any other countries. We use mathematical models to identify processes that could lead to this outcome. In line with previous analyses, we identify a robust quadratic relationship between mean specific humidity and transmission, with minimum transmission occurring at intermediate humidity. This drives semiannual patterns of seasonal transmission rates that peak in summer and winter. Under this transmission regime, a subtle increase in population-level susceptibility can cause a sudden shift in seasonality, where the degree of shift is primarily determined by the interval between the two peaks of seasonal transmission rate. We hypothesize that an increase in children attending childcare facilities may have contributed to the increase in susceptibility through increased contact rates with susceptible hosts. Our analysis underscores the power of studying infectious disease dynamics to titrate the roles of underlying drivers of dynamical transitions in ecology.
确定内源性和外源性驱动因素对宿主-病原体系统动态转变的相对重要性，仍然是预测未来疫情爆发和做出公共卫生决策的一个重要研究前沿。在日本，一种主要的儿童呼吸道病原体——呼吸道合胞病毒（RSV）在2016年爆发季节性出现了突然而显著的转变（从冬季转变为秋季）。这种转变在其他任何国家都未观察到。我们使用数学模型来确定可能导致这一结果的过程。与之前的分析一致，我们发现平均比湿度与传播之间存在稳健的二次关系，在中等湿度下传播率最低。这驱动了季节性传播率的半年模式，在夏季和冬季达到峰值。在这种传播模式下，人群易感性的细微增加可能导致季节性的突然转变，转变程度主要由季节性传播率的两个峰值之间的间隔决定。我们推测，进入托育机构儿童数量的增加，可能通过与易感宿主接触率的增加，导致了易感性的增加。我们的分析强调了研究传染病动态以确定生态中动态转变潜在驱动因素作用的重要性。
