What We Know So Far: COVID-19 Transmission
3 June 2021
At Public Health Ontario (PHO), we are continually monitoring, reviewing and assessing important research on COVID 19 – including how SARS-CoV-2 (the virus that causes COVID 19) passes from one person to another (also called transmission). Most recently, we looked at COVID 19 transmission through large respiratory droplets and smaller droplets known as aerosols (droplets that can be produced when you cough, sneeze, sing, shout and talk).
Here is what we know so far…
Our understanding of COVID 19 transmission has evolved, but the key prevention measures have not changed.
No single public health measure on its own is perfect at preventing the spread of COVID 19, but layers of measures will help provide the best protection. These include:
- getting vaccinated
- staying home when sick and when exposed
- physical distancing and avoiding crowded spaces
- wearing a well-fitting mask in public when physical distancing is not possible
- being outdoors or in well-ventilated indoor spaces
- washing your hands, covering coughs and sneezes, and proper disinfection
Transmission of COVID 19 is complex and depends on many factors
COVID 19 can be transmitted at short-range through large respiratory droplets and smaller respiratory droplets known as aerosols (remember – those droplets from coughing, sneezing, singing, shouting and talking). Long-range transmission through aerosols can occur under specific circumstances, particularly when it is crowded and you are in a closed space with poor ventilation.
- singing, shouting, coughing and sneezing with a lot of force (that pushes the droplets out)
- type of contact with a person who has COVID 19 – the longer and closer contact with an infected person, the higher risk you have
- personal protective measures such as physical distancing, wearing a well-fitted mask and being vaccinated
- the environment – being outdoors or in indoor spaces with good ventilation means lower risk
- amount of virus an infected person has – more virus is present early in an individual’s infection
The bottom line: the best way to prevent COVID 19 is to avoid the “3 C’s”: closed spaces, crowded places and close contact.
If you have specific questions about COVID 19 or think you have been exposed, please contact your local public health unit.
PHO Rounds: Novel Disease Surveillance Tools for the Next Pandemic
This seminar will introduce the concept of informal disease event monitoring systems and how this type of data can and has been used to explore communicable disease epidemiological trends among forcibly displaced persons worldwide.