Ontario's chief medical officer of health says the coming days are critical in Ontario's battle against COVID-19 as hundreds of thousands of people have been returning home to the province, some bringing the virus with them.
Chief Medical Officer of Health Dr. David Williams said it's critical for people who have travelled to isolate themselves for 14 days, and for everyone in the province to practice social distancing and good hygiene.
"This coming weekend and into next week is a very critical time," he said at a media briefing Friday.
Ontario is expecting 200,000 to 500,000 of people to return home in all — and the influx of people, starting last weekend, means that more and more people will be soon be developing symptoms after the virus has incubated since their return.
Williams has been briefing the Queen's Park media regularly since the first reported case of the novel coronavirus in Ontario and for the first time he said there have been verified cases of "community transmission" of the virus in Ontario.
Ontario has seen clusters of cases in long-term care homes in Durham and Haliburton, he said. And there are other cases that have no clear link to a travel history or a confirmed case of the COVID-19 — which could indicate local spread in some communities, but not others, he said.
He called on people to take their responsibility for social distancing seriously, in order to prevent further spread.
Community spread adds an extra layer of complication to the "containment" approach to dealing with the virus that Ontario has used, which requires all people with COVID-19 to self-isolate until they recover, or require hospitalization, while their local public health unit traces the contacts they have had with others.
The idea is that, through what Williams describes as an "immense" amount of work by public health units, the spread of the virus is contained on a case-by-case basis. When there are gaps in that, or when people disregard instructions to isolate themselves, community spread occurs.
Williams said Thursday the containment approach had worked well for the first two phases of COVID-19 in Ontario. In the first, Ontario had cases that stemmed the outbreak in Wuhan — including, at its peak, 5,000 people travelling back and forth from the affected areas of China per day.
The containment strategy also worked for the second phase, when Ontario began to see cases imported from Iran and Italy, both countries that were seeing widespread community transmission of the virus.
"I think that's kept us intact for the first two, but can we continue?" he asked on Thursday.
The third phase, according to Williams, is the people who've returned with the virus from elsewhere, primarily the United States.
Williams explained that with such a vast number of people coming from affected areas back to Canada, public health just doesn't have the workforce to hold the line any longer.
"And that's our challenge," he said. "And that's why we've said we can't just depend on (containment) alone, we have to have the social distancing. We have to declare the state of emergency, we have to close the schools."
What will happens next, according to Williams, is Ontario will continue to see an increasing number of cases as people return from abroad: and some will become sick, there will be more hospitalizations and "hopefully not many deaths — we'll have to see how we do."
The time to reassess the situation will be when most of those people have returned and their 14-day self-isolation period is over, he said.
Williams has been somewhat dismissive of reports from epidemiologists who have modelled the spread of the virus, including recent work by a group from the University Health Network, Sunnybrook Hospital and the Dalla Lana School of Public Health, that even in a "conservative scenario" in which Ontario manages to contain the spread somewhat, Ontario's seriously ill COVID-19 patients will exceed its intensive care unit bed capacity within 37 days.
"Right, you're going to ask the famous question on modelling," he said to one reporter who asked Williams what Ontario's worst-case scenario might look like.
He said that while models are useful to predict different scenarios, they're built on assumptions and reflect the impact of unchecked community transmission. If that was the case, Ontario would have already seen Ontario's hospitals overwhelmed by COVID-19 patients — when there were 22 hospitalized as of Thursday — and far more deaths, weeks ago.
Ontario is performing some sentinel surveillance — which tests people who've presented to emergency departments with respiratory symptoms and respiratory illness outbreaks in long-term care homes for COVID — and so far found all of those tests are negative. According to Williams, if community transmission was widespread that testing should have picked it up.
More of that testing might be done soon, said Williams. The province is ramping up its testing capacity from about 1,000 tests a day as of this week to 3,000 tests a day now, to 5,000 tests a day next week. So far, the limits on the availability of testing has meant the province has focused on people who have travelled, particularly vulnerable people, and health-care workers.
But, according to Williams, once the travel into Ontario slows, public health might be able to use its testing capacity more broadly and capture more cases that might be going missed today.
"So, worst-case scenario, always, is that it goes, you haven't been able to contain it, your social distancing hasn't been able to limit it and it goes widespread, and those numbers start to ramp up," he said, answering the reporter's question.
What that looks like, he said, is northern Italy, where reports have shown hospitals completely swamped by the number of COVID-19 patients and nearly 3,000 deaths.
"It's just overwhelming," he said. "And so, we don't want that situation. I don't think we will. But, one should not be too overconfident, but I am confident in our system, I am confident in our containment processes. I'm confident in Ontarians' response and I'm confident that people coming back will be responsible and do what they're supposed to do."