Issarow Chacha M, Mulder Nicola, Wood Robin
Computational Biology Division, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, South Africa.
The Desmond Tutu HIV Centre, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, South Africa.
R Soc Open Sci. 2018 Jan 17;5(1):170726. doi: 10.1098/rsos.170726. eCollection 2018 Jan.
Tuberculosis (TB) transmission results from the interaction between infective sources and susceptible individuals within enabling socio-environmental conditions. As TB is an airborne pathogen, the transmission probability is determined by the volume of air inhaled from an infected source and the concentration of containing respirable particles (doses) per volume of air. In this study, we model the contributions of infectious dose production, prevalence of infectious cases and daily rebreathed air volume (RAV) for defining the boundary conditions necessary to sustain endemic TB transmission at the population level. Results suggest that in areas with high RAV (range 300-1000 l d), such as prisons, TB transmission is contributed by both super-spreaders (exhaling ≥10 infectious doses hr) and lower infectivity individuals (exhaling less than 10 infectious doses hr). In settings with a low quantity of RAV (less than 100 l d), TB transmission occurs only from super-spreaders. Point-source epidemics occur in low rebreathed environments when super-spreaders infect a number of susceptibles but subsequent transmission is limited by the mean infectivity of secondary cases. By contrast, endemic TB occurs in poor socio-environmental conditions where mean infectivity cases are able to maintain a sufficiently high effective contact number.
结核病（TB）传播是由传染源与易感个体在有利的社会环境条件下相互作用导致的。由于结核病是一种空气传播病原体，传播概率取决于从感染源吸入的空气量以及每单位体积空气中含可吸入颗粒（剂量）的浓度。在本研究中，我们对感染剂量产生、感染病例患病率和每日再呼吸空气量（RAV）的作用进行建模，以确定在人群水平维持结核病地方流行传播所需的边界条件。结果表明，在RAV较高的地区（范围为300 - 1000升/天），如监狱，结核病传播由超级传播者（每小时呼出≥10个感染剂量）和传染性较低的个体（每小时呼出少于10个感染剂量）共同导致。在RAV量较低的环境（少于100升/天）中，结核病传播仅由超级传播者引起。当超级传播者感染一定数量的易感者但后续传播受二代病例平均传染性限制时，在低再呼吸环境中会发生点源流行。相比之下，结核病地方流行发生在社会环境较差的条件下，此时平均传染性病例能够维持足够高的有效接触数。
