BARRIE, ONT. -- With new information circling about how COVID-19 can spread from person to person, just what is the best defence?

CTV's Aileen Doyle finds out from Collingwood General and Marine Hospital's Chief of Staff, Dr. Michael Lisi.

CTV News: We’ve heard a lot about the virus spreading through droplets, but now we hear about aerosols. What’s the best line of defence?

Dr. Lisi: The best line of defence remains the three ‘W’s. Wear a mask, Watch your distance and Wash your hands. Some other useful steps include using outdoor settings when possible when meeting people and avoiding crowds.

CTV News: Fresh air versus. HVAC, which is better ventilation for schools?

Dr. Lisi: So schools or any indoor space benefit from multiple strategies.

First, classes should be held outdoors as much as possible, since studies show that being outdoors is 20 times safer than being indoors. This is a strategy that worked very well for schools in Denmark, for example.

When students have to be indoors, windows should be kept open as much as possible. School furnaces should be adjusted to pull in the maximum amount of fresh air that’s possible.

Buildings should have certain types of filters that can be upgraded, and lastly, there’s portable air purifiers like with HEPA filters, for example. These can be placed in areas identified as having poor ventilation.

CTV News: We’re seeing more cases in parts of Europe and New Zealand. Is this the beginning of their second wave? What can we learn from it ahead of ours, which is anticipated later in autumn?

Dr. Lisi: I think the take-home message is that even in places like New Zealand and Germany that really have been leaders in the response to COVID-19 are still having outbreaks.

And we will almost certainly have to deal with these outbreaks in Ontario in the fall. How many and how severe the outbreaks are going to be is really dependent on us.

If people follow, again - those three ‘W’s: wear a mask, watch your distancing and wash your hands, these outbreaks will be less frequent and smaller.

CTV News: There’s preliminary research, and we’ve seen a few cases where people have gotten COVID-19 twice. What are your thoughts on that?

Dr. Lisi: There is that more well-known case in Hong Kong where that patient had no symptoms. This is medically interesting, yes, but would I worry about this at this point? No.