家庭中的甲流感染一半以上是由长时间悬浮在空气中的呼吸飞沫(来自呼吸的小液滴)传播的。本期Nature Communications上发表的这一发现可帮助制定减少传播的可能措施。在过去,这些措施注重减少接触传播或大液滴传播。
甲流病毒通过接触由感染者在咳嗽或打喷嚏过程中排出的呼吸飞沫传播。流行病学家将呼吸液滴(飞沫)分成较大液滴和较小的传染性液滴:前者在距传播源1-2米内会落到地面;后者直径小于5微米,能较长时间悬浮在空气中,被称为气溶胶。Benjamin Cowling及其同事以这样一个假设为基础:流感的临床表现因传播模式的不同而不同——气溶胶化的甲流病毒引起更像典型流感的症状,表现为发烧和咳嗽;基于大分子的甲流病毒只表现出发烧症状。
据此,他们建立了一个数学模型,来推断每种传播模式对甲流病毒在家庭中传播的贡献。他们利用来自在香港和曼谷的家庭中所进行的两个随机化试验(一个是手部卫生;另一个是戴口罩)的数据来确认该模型,发现用来防止传播的、与手和脸相关的措施并未实质性地改变家庭接触的总体传染风险。这表明,气溶胶传播可能是甲流病毒在住在一起的人员之间传播的主导性模式。(生物谷Bioon.com)
doi:10.1038/ncomms2922
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Aerosol transmission is an important mode of influenza A virus spread
Benjamin J. Cowling, Dennis K. M. Ip, Vicky J. Fang, Piyarat Suntarattiwong, Sonja J. Olsen, Jens Levy, Timothy M. Uyeki, Gabriel M. Leung, J. S. Malik Peiris, Tawee Chotpitayasunondh, Hiroshi Nishiura & James Mark Simmerman
Influenza A viruses are believed to spread between humans through contact, large respiratory droplets and small particle droplet nuclei (aerosols), but the relative importance of each of these modes of transmission is unclear. Volunteer studies suggest that infections via aerosol transmission may have a higher risk of febrile illness. Here we apply a mathematical model to data from randomized controlled trials of hand hygiene and surgical face masks in Hong Kong and Bangkok households. In these particular environments, inferences on the relative importance of modes of transmission are facilitated by information on the timing of secondary infections and apparent differences in clinical presentation of secondary infections resulting from aerosol transmission. We find that aerosol transmission accounts for approximately half of all transmission events. This implies that measures to reduce transmission by contact or large droplets may not be sufficient to control influenza A virus transmission in households.