Toward understanding the risk of secondary airborne infection: Emission of respirable pathogens
Toward understanding the risk of secondary airborne infection: Emission of respirable pathogens
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DOI：
10.1080/15459620590918466
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发表时间：
2005-03-01
影响因子：
2
通讯作者：
Hubbard, A
中科院分区：
文献类型：
--
作者：
Nicas, M;Nazaroff, WW;Hubbard, A
某些呼吸道感染通过空气传播。感染者咳嗽、打喷嚏时，会散发出直径小于10微米的含病原体颗粒，可到达肺泡区。根据我们对稀少的呼吸气溶胶文献的分析，我们估计，由于水分损失，排放的颗粒物直径迅速减小到初始值的一半，一次咳嗽时，初始直径小于20微米的物品的体积为6×10(-8)毫升。病源病例的病原体发射率取决于呼气事件的频率、可吸入颗粒物的体积和呼吸液中的病原体浓度。可通过排气通风、颗粒沉降、消亡和空气消毒等方法去除空气中可存活的病原体：每种去除机制都可以分配一个一级速率常数。混合良好的房间空气中的病原体浓度取决于排放率、携带病原体的可吸入颗粒物的尺寸分布和去除速率常数。颗粒沉降率和肺泡沉积率与颗粒大小有关。考虑到这些输入加上易感人群的呼吸频率和暴露在室内空气中的持续时间，估计出预期的肺泡量P。如果感染剂量是一种生物，就像结核病的情况一样，感染风险通过以下表达式来估计：R=1-exp(-u)。使用已发表的关于咳嗽频率、呼吸液中细菌浓度和死亡率的结核病数据，我们通过一个看似合理的情景来说明该模型，该情景适用于一个肺结核病例的房间。我们建议，被称为“超级传播者”或“危险传播者”的患者是那些罕见的人，他们咳嗽和/或打喷嚏的频率很高，呼吸道、液体中的病原体浓度升高，和/或每个呼气事件的可呼吸气雾剂体积增加，以至于他们的病原体发射率远远高于平均水平。
Certain respiratory tract infections are transmitted through air. Coughing and sneezing by an infected person can emit pathogen-containing particles with diameters less than 10 mu m that can reach the alveolar region. Based on our analysis of the sparse literature on respiratory aerosols, we estimated that emitted particles quickly decrease in diameter due to water loss to one-half the initial values, and that in one cough the volume in articles with initial diameters less than 20 mu m is 6 x 10(-8) mL. The pathogen emission rate from a source case depends on the frequency of expiratory events, the respirable particle volume, and the pathogen concentration in respiratory fluid. Viable airborne pathogens are removed by exhaust ventilation, particle settling, die-off, and air disinfection methods: each removal mechanism can be assigned a first-order rate constant. The pathogen concentration in well-mixed room air depends on the emission rate, the size distribution of respirable particles carrying pathogens, and the removal rate constants. The particle settling rate and the alveolar deposition fraction depend on particle size. Given these inputs plus a susceptible person's breathing rate and exposure duration to room air, an expected alveolar dose P is estimated. If the infectious dose is one organism, as appears to be true for tuberculosis, infection risk is estimated by the expression: R = 1 - exp(-mu). Using published tuberculosis data concerning cough frequency, bacilli concentration in respiratory fluid, and die-off rate, we illustrate the model via a plausible scenario for a person visiting the room of a pulmonary tuberculosis case. We suggest that patients termed "superspreaders" or "dangerous disseminators" are those infrequently encountered persons with high values of cough and/or sneeze frequency, elevated pathogen concentration in respiratory, fluid, and/or increased respirable aerosol volume per expiratory event such that their pathogen emission rate is much higher than average.