Coughs and Sneezes: Their Role in Transmission of Respiratory Viral Infections, Including SARS-CoV-2

Abstract

Coughs and sneezes disperse a large number of droplets of varying size into the environment, and they transmit respiratory viral infections by direct or indirect physical contact, by droplets or inhalation of fine particulate droplet nuclei. Larger droplets in the cloud produced by coughing and sneezing settle quickly, and the force with which they are expelled determines how far they are dispersed. The respiratory droplets evaporate to form smaller droplet nuclei that carry infectious agents, remain suspended in air, and susceptible individuals farther away from the source could inhale them. The particle size distribution within the multi-phase cloud produced by coughs/sneezes changes with time and distance from the source depending on several environmental factors. After inhalation, larger respiratory droplets are filtered by the nose or deposit in the oropharynx, whereas smaller droplet nuclei are carried by the airstream into the lungs where their site of deposition depends on their mass, size and shape and is governed by various mechanisms. Airborne particles could also be produced by various aerosol generating procedures, such as suctioning or tracheal intubation, and by aerosol generators, especially jet nebulizers. Prevention of respiratory viral infections depends upon whether they are carried in respiratory droplets or as fine droplet nuclei (airborne or aerosol transmission). The SARS-CoV-2 virus that causes COVID-19 is mainly transmitted by respiratory droplets or by contact. Airborne transmission of this virus has not been established, but is possible under special circumstances. Appropriate protective measures are necessary to prevent transmission of SARS-CoV-2 virus in various settings. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).