As coronavirus spread across China, researchers there moved quickly to follow it.

The result was a study of thousands of cases that reveals how the outbreak may affect Canadians across age and gender, and who is most at risk — those aged 80 and older and a higher proportion of men compared to women.

The study also shows that the disease is “highly contagious,” according to its authors, and continued to be transmitted across China even as officials in that country took extreme measures to shut it down.

How it will spread in Canada remains to be seen.

“China implemented some pretty significant measures to combat this,” said Toronto epidemiologist Jeff Kwong. “They locked down tens of millions of people and they did a lot of what we call contact tracing.”

Yet, according to the study, the virus “spread extremely rapidly from a single city to the entire country within only about 30 days.”

“Moreover, it has achieved such far-reaching effects even in the face of extreme response measures,” says the study, “including the complete shutdown and isolation of whole cities, cancellation of Chinese New Year celebrations, prohibition of attendance at school and work, massive mobilization of health and public health personnel as well as military medical units, and rapid construction of entire hospitals.”

The research, which was reviewed and fast-tracked by the China Centre for Disease Control and Prevention Institutional Review Board, looked at more than 70,000 incidents and calculated age, gender and severity, among other factors, for 44,672 confirmed cases. It was published in China CDC Weekly.

We asked Kwong, who is associate director of the University of Toronto’s Centre for Vaccine Preventable Diseases and a family doctor at Toronto Western Hospital, what could happen here.

This interview has been edited for clarity and length.

Is the data from China representative of what could happen elsewhere?

It’s not like it’s a study of the first 50 cases, the report is based on nearly 50,000 lab-confirmed cases. I would expect that we’re going to see that same pattern elsewhere.

What about the breakdown by age? Is that fairly representative of what could happen in Canada?

It depends on the population. That’s the thing.

Let’s say that this disease affects older people the most, which is what we’re seeing from the study. We happen to have more older people in Canada relative to the overall population than China.

Italy is quite a bit older still than Canada, so you can see why their hospitals are at capacity, from what I’ve read.

Would you expect to see the same severity of cases here as in China?

I think, if anything — because we have a slightly older population — we may end up seeing more severe cases here.

But, on the other hand, because there’s less pollution here and lower rates of smoking, maybe we won’t see as many severe cases as China. It’s hard to say.

Looking at the data, at what age do people become more susceptible?

I’d say the risk really starts increasing at age 60.

When a case is considered critical, what does that mean?

Critical would refer to a case where people have so much fluid in their lungs that they can’t breathe anymore, what we call consolidation.

It’s like a really bad pneumonia, or their lungs are failing. Then we have to put them on ventilators.

The case fatality rate in the study was 2.8 per cent for men and 1.7 per cent for women. Would you expect it to be similar here?

I think the case fatality rates are likely to be similar here. An 80-year-old in China is not that different than an 80-year-old in Canada.

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The only difference is how many 80-year-olds there are in China as a proportion of the entire population.

And then the question is, how many hospital beds do you have?

If you were younger, wouldn’t you want to get the virus so that you could be immune to it?

There are definitely people who are thinking that — but our goal is to protect those most vulnerable.

We used to do things like chickenpox parties, but the risky thing here is — let’s say you do get it, and you’re young. You could have a really mild infection and not realize you’re spreading it to someone who is vulnerable. So you go visit your parents, or your grandparents and you give it to them, and they get really sick.

How much more deadly than the flu is COVID-19?

With seasonal influenza, there is about 0.1 per cent chance of dying. If you look at reported cases of the novel coronavirus, it’s around 2 per cent.

But if you factor in all the unreported cases, then the percentage that are fatal would go down. So maybe the true per cent of fatalities is lower — but still a lot more significant than influenza. And the other thing with influenza is that only 10 or 15 per cent of the population will get it in a season.

What did you think of the figure federal health minister Patty Hajdu used — that 30 to 70 per cent of the population could be infected?

It’s a big number. There’s no getting around that — you have a population of 37 million.

The thing to keep in mind, when they say 30 to 70 per cent it’s not like tomorrow, 30 to 70 per cent of Canadians are going to have it. It’s not like we may even reach that proportion in a year. That may be the number over the next three or five years.

Will it be like the flu and come back every year?

That’s what we don’t know. We don’t know if it’s going to continue on through the spring or summer. Or if it will be like the other respiratory diseases that tend to go away in the summer and come back in the next fall/winter.

Why do viruses like the flu come and go?

Nobody knows why. We know that influenza viruses like cold and dry weather, or they like hot and humid.

So in temperate countries like Canada, where you have four seasons, you get a flu season in the winter. But in certain tropical countries closer to the equator, they’ll have influenza circulating year around. But why they go away we don’t know

What would you expect this virus to do?

It’s anyone’s guess at this point.

If anyone says they know what’s going to happen, they’re just guessing.