WHO issued an updated scientific brief on COVID-19 transmission, which provides information on how, when and in which settings the virus spreads between people.
COVID-19 transmission occurs primarily through direct, indirect or close contact with infected people through their saliva and respiratory secretions, or through their respiratory droplets, which are expelled when they cough, sneeze, talk or sing.
Airborne COVID-19 transmission can occur in health care settings where specific medical procedures generate very small droplets – aerosols.
Some COVID-19 outbreak reports related to crowded indoor spaces have suggested the possibility of aerosol transmission combined with droplet transmission e.g. during choir practice, in restaurants or gyms. We need more studies to understand such outbreaks: https://bit.ly/2W251Ma
Respiratory droplets from infected individuals can also land on objects or other surfaces. It is likely that people can also be infected with COVID-19by touching these surfaces & touching their Eyes, Nose or Mouth before cleaning their Open hands.
Based on what we currently know, COVID-19 transmission primarily occurs when people are showing symptoms, but can also happen just before they develop symptoms – when they are in close proximity to others for prolonged periods of time.
While people who never develop COVID-19 symptoms can also pass the virus to others, it is still not clear to what extent this occurs. More research is needed in this area.
Urgent research is needed on:
-airborne transmission in the absence of aerosol generating procedures
-dose of virus that will result in infection
-settings and risk factors for superspreading events
-extent of asymptomatic and pre-symptomatic transmission
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