Global Perspective Article
Airborne spread of infectious agents in the indoor environment

https://doi.org/10.1016/j.ajic.2016.06.003Get rights and content

Highlights

  • Different stages of the spread of infectious agents were analyzed.

  • Short-range airborne route is potentially very important.

  • Short-range airborne route may be controlled by masks and personalized ventilation.

  • Displacement ventilation may not be applicable to control respiratory diseases.

Background

Since the 2003 severe acute respiratory syndrome epidemic, scientific exploration of infection control is no longer restricted to microbiologists or medical scientists. Many studies have reported on the release, transport, and exposure of expiratory droplets because of respiratory activities. This review focuses on the airborne spread of infectious agents from mucus to mucus in the indoor environment and their spread as governed by airflows in the respiratory system, around people, and in buildings at different transport stages.

Methods

We critically review the literature on the release of respiratory droplets, their transport and dispersion in the indoor environment, and the ultimate exposure of a susceptible host, as influenced by airflows.

Results

These droplets or droplet nuclei are transported by expired airflows, which are sometimes affected by the human body plume and use of a face mask, as well as room airflow. Room airflow is affected by human activities such as walking and door opening, and some droplets are eventually captured by a susceptible individual because of his or her inspired flows; such exposure can eventually lead to long-range spread of airborne pathogens. Direct exposure to the expired fine droplets or droplet nuclei results in short-range airborne transmission. Deposition of droplets and direct personal exposure to expired large droplets can lead to the fomite route and the droplet-borne route, respectively.

Conclusions

We have shown the opportunities for infection control at different stages of the spread. We propose that the short-range airborne route may be important in close contact, and its control may be achieved by face masks for the source patients and use of personalized ventilation. Our discussion of the effect of thermal stratification and expiratory delivery of droplets leads to the suggestion that displacement ventilation may not be applicable to hospital rooms where respiratory infection is a concern.

Key Words

Respiratory droplet
indoor air
coughing
droplet dispersion
infection control
environmental ventilation

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Funding/Support: This research was funded by the Research Grants Council General Research Fund (HKU7142/12) and the Natural Science Foundation of China (51278440). Publication of this supplement is primarily supported by RB, Montvale, New Jersey, with additional support from MicroBioTest, a division of Microbac Laboratories, Inc., Sterling, Virginia. The City University of New York (CUNY) and the University of Ottawa, Ottawa, Canada, are academic sponsors. Editorial support was provided by Ashley O'Dunne, PhD; Shannon O'Sullivan, ELS; and Alanna Franchetti, ELS of Medergy (Yardley, PA), and funded by RB.

Conflicts of Interest: None to report.

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