COVID19 Modes of Transmission
How a person gets infected with COVID19 virus
There's still a lot we don't know for sure about the way the virus that causes COVID-19 spreads.
Although there are at the moment 3 most commonly theorized ways of transmission, namely, 1) droplet transmission; 2) surface transmission; and 3) airborne transmission, in most individual persons, we do not know exactly how the person got infected.
Droplet Transmission
An infected person is talking, coughing or sneezing within close contact of others. Large respiratory droplets (greater than 5μm to 10μm) makes direct contact to infect.
Surface Transmission
A person touches a contaminated surface and then inadvertently touches their face, introducing the virus.
Airborne (Aerosol) Transmission
An infected person is talking, coughing or sneezing. The small respiratory droplets (less than 5μm to 10μm) remain suspended in air for a period of time and over greater distance.
WHO
According to current evidence, COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes.
Droplet transmission occurs when a person is in in close contact (within 1 m) with someone who has respiratory symptoms (e.g., coughing or sneezing) and is therefore at risk of having his/her mucosae (mouth and nose) or conjunctiva (eyes) exposed to potentially infective respiratory droplets. Transmission may also occur through fomites in the immediate environment around the infected person.8 Therefore, transmission of the COVID-19 virus can occur by direct contact with infected people and indirect contact with surfaces in the immediate environment or with objects used on the infected person (e.g., stethoscope or thermometer).
Airborne transmission is different from droplet transmission as it refers to the presence of microbes within droplet nuclei, which are generally considered to be particles <5μm in diameter, can remain in the air for long periods of time and be transmitted to others over distances greater than 1 m.
In the context of COVID-19, airborne transmission may be possible in specific circumstances and settings in which procedures or support treatments that generate aerosols are performed; i.e., endotracheal intubation, bronchoscopy, open suctioning, administration of nebulized treatment, manual ventilation before intubation, turning the patient to the prone position, disconnecting the patient from the ventilator, non-invasive positive-pressure ventilation, tracheostomy, and cardiopulmonary resuscitation.
Based on the available evidence, including the recent publications mentioned above,
WHO continues to recommend droplet and contact precautions for those people caring for COVID-19 patients.
WHO continues to recommend airborne precautions for circumstances and settings in which aerosol generating procedures and support treatment are performed, according to risk assessment.13
Current WHO recommendations emphasize the importance of rational and appropriate use of all PPE, not only masks, which requires correct and rigorous behavior from health care workers, particularly in doffing procedures and hand hygiene practices.
WHO also recommends staff training on these recommendations, as well as the adequate procurement and availability of the necessary PPE and other supplies and facilities.
Finally, WHO continues to emphasize the utmost importance of frequent hand hygiene, respiratory etiquette, and environmental cleaning and disinfection, as well as the importance of maintaining physical distances and avoidance of close, unprotected contact with people with fever or respiratory symptoms.
Does COVID-19 Spread through Droplets Alone?
To answer this question, we provide epidemiological observational data in conjunction with known molecular characteristics of SARS-CoV-2. We discuss the ability of this novel coronavirus to remain viable on environmental surfaces from hours to days and describe its increased virulence characteristics compared to the previous SARS-CoV-1. These biochemical and molecular properties likely allow this novel coronavirus to employ indirect methods of transmission, including fomites and aerosols, in addition to respiratory droplet transmission (Figure 1).
The current consensus regarding the transmission of SARS-CoV-2 is that it spreads person to person through respiratory droplets (5, 6). Precautions to prevent the spread by droplets as recommended by both the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) are to (1) wash hands with soap, (2) avoid touching viral entry points, such as eyes, nose, and mouth, (3) cover the mouth when coughing or sneezing, (4) wear a facemask if sick and (5) practice social distancing by putting 6 feet of distance between individuals. In addition to these precautions, government-mandated social distancing measures such as (6) state lockdowns and (7) “stay at home” orders are effective ways to minimize the spread of SARS-CoV-2 through droplet transmission.
https://www.frontiersin.org/articles/10.3389/fpubh.2020.00163/full
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