The transmission risk of COVID-19 is not fully elucidated as of now. An initial association is predicted to be with animals at a live animal market in Wuhan.
In the case of rapid spread among the population, however, person to person spread is considered the main mode of transmission. The spread may occur in the following ways:
- Droplet transmission
- It occurs when a person is in close contact (within 2 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.
- Droplets typically do not travel more than six feet (about two meters) and do not linger in the air.
- Contact transmission
- Transmission may also occur through fomites in the immediate environment around the infected person. Therefore, the 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
- 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, the 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.
- Feco-oral transmission:
- Though the live virus has been cultured from stool in some cases, the fecal-oral transmission did not appear to be a significant factor in the spread of infection.
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.
Preventive Steps according to Mode of Transmission:
- Universal Standard Precautions:
- Hand hygiene, proper washing of hands before and after patient contact
- Use of appropriate protective equipment (i.e., gloves) before patient contact
- Respiratory hygiene (i.e., covering your cough and sneeze)
- Injection and sharp object safety and proper disposal
- Cleaning of supplies and disposal of waste
- Contact precautions
- PPE defined by the CDC required before entering a contact precaution designated room is always gloves and a gown.
- Mask and eye protection are additionally required if contact with bodily secretions is possible.
- Droplet precautions:
- Patients should be placed in individualized rooms, if possible.
- In addition to standard precautions, personnel should wear protective surgical masks should always before interacting between an infected patient or his/her environment.
- Airborne precautions:
- In addition to standard precautions of wearing gloves and a gown, the CDC requires additional PPE of an approved N95 respirator mask properly fitted for each person working in the health-care environment.
- The CDC also strongly recommends placing patients diagnosed with or receiving testing for, with high suspicion of an infectious airborne organism in a single room known as an airborne infection isolation room (AIIR). These are negative pressure rooms that provide air filtration and 6 to 12 air exchanges per hour to reduce the risk of transmission.
- Whenever interacting with any patient in a health-care facility, health-care team members and visitors need to adhere to and comply with PPE and infection control signs. It is also essential to wash hands thoroughly with soap and water before and when leaving a patient’s room to ensure the safety of the patient and oneself.