The recent study of US Centres for Disease Control and Prevention (CDC) said that the exposure to the respiratory fluids and the fine respiratory droplets and aerosol particles, which are present in air and carry the viruses are the main reason for contracting Covid-19 infection.
People release the respiratory fluids while they exhale like quiet breathing, speaking, singing, exercise, coughing, sneezing in the form of droplets. However, the large droplets flump out of the air within seconds to minutes. The very fine droplets can remain suspended in the air for minutes to hours. The latest science brief of the agency clarify as part of its public guidelines on Covid-19 by stating that the droplets carry viruses and transmit infections.
The revelation to these droplets occurs in three principal way. Firstly, the very fine respiratory droplets and aerosol particles are inhaled. Further, the deposition of respiratory droplets on exposed mucous membranes in the mouth, nose, or eye by direct splashes and sprays. The last one is touching the mucous membranes with hands that have been soiled. This can happen either directly by virus-containing respiratory fluids or indirectly by touching surfaces with virus on them.
The CDC, USA said, “the risk of SARS-CoV-2 infection varies according to the amount of virus to which a person is exposed.” Further, they stated , “it can be sufficient to transmit infections to people more than 6 feet away, and in some cases to people who have passed through that space soon after the infectious person left. The risk in this case is more in enclosed spaces with inadequate ventilation.”
Infections through inhalation at distances greater than six feet from an infectious source are less likely than at closer distances. But, when an infectious person exhales virus indoors for an extended time. Thus, more than 15 minutes and in some cases hours, it can lead to virus concentrations in the air space.