Canadian public health guidance related to COVID-19 has been changing as the evidence base and understanding of the illness is rapidly evolving, states a press release from the Council of Chief Medical Officers.
"We are continually looking at the evidence as it is being produced and working with our partners across the country and around the world to learn more," the release states.
The council explains that now more countries have had large numbers of cases and have analysed transmission patterns, recent studies provide evidence that transmission of the virus can happen from infected people, before they develop symptoms. This is refereed to as pre-symptomatic transmission.
According to the council, there is also evidence that some infected people who never develop symptoms are also able to transmit the virus. This is called asymptomatic transmission.
The council admits in the release that researchers do not know how much of a role pre-symptomatic and asymptomatic transmission play in driving the epidemic at this time, but say they know it is occurring among those with close contact or in close physical settings.
While the primary driver of the global pandemic of COVID-19 has been individuals with visible symptoms (coughing and respiratory droplets are key ways the virus is spread), evidence of asymptomatic or pre-symptomatic transmission points to the importance of everyone, even those who feel fine, following the proven methods of preventing transmission, the release states.
The council advises these measures to prevent transmission of COVID-19:
• Staying home as much as possible;
• Physical distancing;
• Washing your hands;
• Protecting the most vulnerable from infection and exposure to others;
• Covering your cough with tissues or your sleeve;
The council also advocates for health-care workers using medical masks, including surgical, medical procedure masks and respirators such as N95 masks.
"It is extremely important that we keep the supply of medical masks for healthcare workers where it is urgently needed for medical procedures and to care for individuals who have COVID-19," the release states.
The group adds that wearing a non-medical mask (homemade cloth mask) in the community has not been proven to protect the person wearing it. However, the use of a non-medical mask or facial covering can be an additional measure to protect others.
Wearing a non-medical mask is another way of covering the mouth and nose to prevent respiratory droplets from contaminating others or landing on surfaces.
For short periods of time, when physical distancing is not possible in public settings (grocery shopping, in close settings such as public transit), wearing a non-medical mask is one way to protect those around you, the council states.
Wearing a non-medical mask when in public or other settings is not a replacement for following proven measures such as hand washing and physical distancing, the council warns.
"Canadians need to understand exactly what wearing a mask will achieve, and that if they choose to wear non-medical masks they need to be used safely. The website Canada.ca/coronavirus is updated with information on the measures to take, such as hand washing, when putting a mask on or taking it off. There is also information on how to wash cloth masks or safely dispose of other non-medical masks (such as dust masks)," the press release states.
Those who choose to use a non-medical mask, should ensure well-fitted (non-gaping). People should also be aware that masks can become contaminated on the outside or when touched by hands. Avoid moving the mask around or adjusting it often. Also, masks should not be shared with others.
This is advice from the Council of Chief Medical Officers.
