School of Computing and Information Systems, The University of Melbourne, Australia.
School of Computing and Information Systems, The University of Melbourne, Australia; Department of Infectious Diseases, The University of Melbourne, Australia.
J Theor Biol. 2022 Sep 7;548:111185. doi: 10.1016/j.jtbi.2022.111185. Epub 2022 Jun 11.
Multi-strain pathogens such as Group A Streptococcus, Streptococcus pneumoniae, and Staphylococcus aureus cause millions of infections each year with a substantial health burden. Control of multi-strain pathogens can be complicated by the high strain diversity often observed in endemic settings. It is not well understood how high strain diversity is maintained in populations, given that they compete with each other both directly (within an individual host) and indirectly (via host immunity). Previous modelling studies have investigated how indirect competition affects the prevalence and diversity of strains. However, these studies often make simplifying assumptions about the direct competition that occurs within hosts. Currently, little data is available to validate these assumptions, hence there is a need to clarify how sensitive model outputs are to these assumptions. In this study, we compare the dynamics of multi-strain pathogens under different assumptions about direct competition between strains using an agent-based model. We find that the assumptions made about direct competition can affect the epidemiological dynamics, particularly when there is no long-term immunity following infections and a low rate of importation of non-circulating strains. Our results suggest that while direct and indirect competition can each decrease strain diversity when they act in isolation, they may increase strain diversity when they act together. This finding highlights the importance of examining sensitivity to assumptions about strain competition. In particular, omitting consideration of direct competition can lead to inaccurate estimates of the likely effectiveness of control strategies as changes in strain diversity shift the level of direct strain competition.
多菌株病原体，如 A 组链球菌、肺炎链球菌和金黄色葡萄球菌，每年导致数百万人感染，造成巨大的健康负担。在地方性流行环境中，通常观察到菌株多样性较高，因此控制多菌株病原体可能变得复杂。尽管它们在个体宿主内直接（直接竞争）和间接（通过宿主免疫）相互竞争，但人们尚不清楚如何在人群中维持高菌株多样性。以前的建模研究已经调查了间接竞争如何影响菌株的流行和多样性。然而，这些研究经常对宿主内发生的直接竞争做出简化假设。目前，可用的数据很少，可以验证这些假设，因此需要澄清模型输出对这些假设的敏感性。在这项研究中，我们使用基于主体的模型，比较了在菌株之间直接竞争的不同假设下多菌株病原体的动态。我们发现，关于直接竞争的假设可以影响流行病学动态，特别是在感染后没有长期免疫和非循环菌株的低输入率的情况下。我们的结果表明，虽然直接和间接竞争在孤立作用时都可以降低菌株多样性，但它们在共同作用时可能会增加菌株多样性。这一发现强调了检查对菌株竞争假设的敏感性的重要性。特别是，忽略对直接竞争的考虑可能会导致对控制策略的有效性的估计不准确，因为菌株多样性的变化会改变直接菌株竞争的水平。
