Instituto Gulbenkian de Ciência, Apartado 14, 2781-901 Oeiras, Portugal.
Proc Biol Sci. 2012 Jun 22;279(1737):2473-8. doi: 10.1098/rspb.2011.2712. Epub 2012 Feb 22.
Recurrent episodes of tuberculosis (TB) can be due to relapse of latent infection or exogenous reinfection, and discrimination is crucial for control planning. Molecular genotyping of Mycobacterium tuberculosis isolates offers concrete opportunities to measure the relative contribution of reinfection in recurrent disease. Here, a mathematical model of TB transmission is fitted to data from 14 molecular epidemiology studies, enabling the estimation of relevant epidemiological parameters. Meta-analysis reveals that rates of reinfection after successful treatment are higher than rates of new TB, raising an important question about the underlying mechanism. We formulate two alternative mechanisms within our model framework: (i) infection increases susceptibility to reinfection or (ii) infection affects individuals differentially, thereby recruiting high-risk individuals to the group at risk for reinfection. The second mechanism is better supported by the fittings to the data, suggesting that reinfection rates are inflated through a population phenomenon that occurs in the presence of heterogeneity in individual risk of infection. As a result, rates of reinfection are higher when measured at the population level even though they might be lower at the individual level. Finally, differential host recruitment is modulated by transmission intensity, being less pronounced when incidence is high.
结核病（TB）的复发可能是由于潜伏感染的复发或外源性再感染引起的，因此区分这两者对于控制规划至关重要。结核分枝杆菌分离株的分子基因分型为衡量再感染在复发性疾病中的相对贡献提供了具体机会。在这里，我们拟合了结核病传播的数学模型，以适应来自 14 项分子流行病学研究的数据，从而能够估计相关的流行病学参数。荟萃分析表明，成功治疗后的再感染率高于新结核病的发病率，这就提出了一个关于潜在机制的重要问题。我们在模型框架内提出了两种替代机制：（i）感染增加了再感染的易感性，或（ii）感染对个体产生不同的影响，从而将高危个体招募到再感染风险群体中。数据拟合更支持第二种机制，这表明再感染率是通过个体感染风险异质性存在时发生的群体现象而膨胀的。因此，即使在个体水平上再感染率可能较低，但在人群水平上测量时，再感染率更高。最后，宿主的差异招募受到传播强度的调节，当发病率较高时，其影响程度较小。
