Province at risk of doubling daily cases
Analysis suggests as many as 1,700 new infections per day within a month
The number of new daily cases of COVID-19 in Ontario will almost double in the next month if the current reproduction number of the virus continues, according to a new analysis.
The province’s reproduction number currently sits at 1.08, meaning for every infectious person, 1.08 people will become infected. If this number doesn’t go down, we could see as many as 1,700 new cases per day in the next 30 days, according to Ryan Imgrund, a biostatistician with Southlake Regional Health Centre. The rolling seven-day average of new daily cases of COVID-19 in Ontario is 1,019.
But if the province sees 1,700 new daily cases, it’s unclear if Toronto will stay in the new “restrict” category that it is supposed to enter on Nov. 14, according to the province’s new framework, which will determine how each public health unit tightens or eases pandemic restrictions.
The reproduction number, along with infection rates, level of community transmission and hospital capacity are some of the factors that will determine whether restaurants, bars, gyms and theatres reopen, as long as certain protective measures are taken.
Imgrund says the risk of transmission isn’t necessarily about what locations are reopened, but rather, the precautions put in place.
“A gym isn’t necessarily a bad place. If heavy cardio is being done in a masked environment with good ventilation, it may not have an impact on case numbers,” he said. “But if we have people at a gym working out unmasked and gathering, that’s a problem. But the same can be said for any environment. Especially indoor ones.”
If Toronto does enter the “restrict” category, intermediate measures will be put in place that include capping private social gatherings at 10 people indoors and at 25 for outdoor gatherings.
Limits for organized public events and social gatherings will remain at 50 people indoors and 100 people outdoors. Restaurants and bars will be limited to 50 people indoors with a maximum of four people at a table. Gyms and cinemas would also be capped at that number.
Imgrund, who has been calculating the reproduction number of the virus daily, has also been calculating risk based on the size of gatherings in Toronto data and has broken the down into risk for individual neighbourhoods.
Currently, his data shows that in a group of 50, such as a restaurant or a gym with that number of people in it, the risk of encountering someone with COVID remains high this week in Toronto, with a nearly onein-five chance, unchanged from last week.
In groups of a hundred, the risk is one in three.
Imgrund’s analysis shows that the risk varies depending on which Toronto neighbourhood you’re in. In a third of the city’s neighbourhoods, the risk of encountering COVID ranges from 25 per cent to 50 per cent in groups of 50; double the group size and the risk is one in four in 80 neighbourhoods.
In a group of 500, the risk increases to 88 per cent; in a group of 1,000, the risk is 98.6 per cent.
To calculate the risk percentages, Imgrund uses case data by postal code released by the city of Toronto every week. He assumes that the virus is transmissible for a period of 12 days and takes into account the fact that people can transmit COVID-19 before and after the onset of symptoms.
He also accounts for the population of each neighbourhood and uses seroprevalence figures from Public Health Ontario, which is testing for antibodies specific to COVID-19 in blood samples to determine the proportion of the population that has been infected.
The province’s new framework will determine how each public health unit tightens or eases restrictions