Transmission of COVID-19 can occur through direct, indirect, or close contact with an infected person via the respiratory droplets and aerosols that they generate by coughing, sneezing, singing, shouting, or talking. The droplets can vary in size; larger droplets fall to the ground relatively quickly and smaller droplets – commonly referred to as aerosols – linger in the air for longer periods of time.
A person becomes infected when virus-containing aerosols or droplets come into direct contact with the mucous membranes of their nose, eyes, or mouth. They can also be inhaled through the nose, mouth, airways, and lungs. It can also spread through “self-inoculation”, which is when a person touches an infected surface and then goes on to touch their face, increasing the likelihood of the pathogen to encounter their mucous membranes.
Modes of transmission of COVID-19 include:
- Contact: COVID-19 could be transmitted from an infected to a healthy individual due to close (direct or indirect) physical interactions between them
- Droplet: can occur when a person is in close contact with an infected person who has respiratory symptoms. Talking, singing or yelling can allow for these respiratory droplets to reach the mouth, nose, or eyes of a susceptible person, causing infection
- Airborne: occurs when virus-containing droplets in the air are inhaled by an individual. It was debated whether SARS-Cov-2 was transmitted through this route, as it was initially thought to be too bulky and heavy to be able to be taken up into aerosols; thus, it could only reside in droplets that would fall onto surfaces. It has now been determined that SARS-CoV-2 is an airborne disease as well, and infection can be caused through inhalation as well as mucous membrane contact
- Fomite: refers to the creation of contaminated surfaces (fomites) through droplets or secretions expelled by infected individuals. Active virus can be detected on these surfaces for periods ranging from hours to days, which is why disinfecting surfaces is a vital technique for combatting SARS-CoV-2
- Fecal-oral: a route of transmission in which fecal particles from an infected person are passed on to the mouth of a susceptible individual. Routes of fecal-oral transmission remain uncertain, but it is suspected that it can occur if the infected person does not wash their hands properly after using the bathroom and contaminates surfaces