THE INFLUENCE OF INCREASING LIFE EXPECTANCY ON THE DYNAMICS OF SIRS SYSTEMS WITH IMMUNE BOOSTING
THE INFLUENCE OF INCREASING LIFE EXPECTANCY ON THE DYNAMICS OF SIRS SYSTEMS WITH IMMUNE BOOSTING
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DOI：
10.1017/s1446181113000023
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发表时间：
2012-10-01
期刊：
影响因子：
0.9
通讯作者：
Mccaw, J. M.
中科院分区：
文献类型：
--
作者：
Dafilis, M. P.;Frascoli, F.;Mccaw, J. M.
地方性传染病不断在人群中传播，流行率在一个（理论上和未观察到的）不依赖于时间的平衡点上下波动。对于获得性免疫不是终身的疾病，经典的易感-感染-恢复-易感（SIRS）模型提供了一个框架，在此框架内考虑观察到的流行病学的时间趋势。然而，在某些情况下（特别是百日咳），观察到持续多年的波动，而SIRS模型的特点是阻尼振荡动力学模型参数的所有生物意义的选择。我们表明，一个模型，允许“提升”的免疫力可能会自然地产生无阻尼振荡行为的生物现实的参数选择。人口的预期寿命是决定系统动态特征的关键。对于预期寿命高达约50年，我们发现，即使与升压，阻尼振荡动态持续。为了增加寿命，系统可能维持振荡动力学，甚至表现出稳定点吸引子和极限环动力学共存的振荡行为。我们的研究结果表明，预期寿命的增加可能会引起免疫力不是终身的感染的特征动力学的变化，对疾病控制策略具有潜在的影响。
Endemic infectious diseases constantly circulate in human populations, with prevalence fluctuating about a (theoretical and unobserved) time-independent equilibrium. For diseases for which acquired immunity is not lifelong, the classic susceptible-infectious-recovered-susceptible (SIRS) model provides a framework within which to consider temporal trends in the observed epidemiology. However, in some cases (notably pertussis), sustained multiannual fluctuations are observed, whereas the SIRS model is characterized by damped oscillatory dynamics for all biologically meaningful choices of model parameters. We show that a model that allows for "boosting" of immunity may naturally give rise to undamped oscillatory behaviour for biologically realistic parameter choices. The life expectancy of the population is critical in determining the characteristic dynamics of the system. For life expectancies up to approximately 50 years, we find that, even with boosting, damped oscillatory dynamics persist. For increasing life expectancy, the system may sustain oscillatory dynamics, or even exhibit bistable behaviour, in which both stable point attractor and limit cycle dynamics may coexist. Our results suggest that rising life expectancy may induce changes in the characteristic dynamics of infections for which immunity is not lifelong, with potential implications for disease control strategies.