By Allison Martell and Moira Warburton

TORONTO/VANCOUVER (Reuters) – Canada’s three biggest provinces are seeing a pick-up in new COVID-19 cases, as officials do little to slow the virus beyond urging people to be more careful, and doctors warn school reopenings will boost demand for testing.

The country reported no deaths for one day on Friday, an echo of earlier success in controlling the virus that may already be slipping away, even before the impact of school reopenings is clear.

Demand for tests is already up in some Ontario hot spots, and will rise further as more children return to school. Students with symptoms will generally have to isolate at home until they are well and have a negative test, so any backlogs will trap families at home.

McMaster University infectious disease expert Dr Zain Chagla said assessment centers need to stop testing asymptomatic people who have no known exposure to the virus, before labs become overwhelmed.

Canada’s 5 million school children average about eight upper respiratory tract infections a year, said Chagla. Even if that falls to two this year, some 27,000 will need to be tested on any given day.

Last week, Canada averaged 47,807 tests per day.

“It’s not minor, the actual demands that are going to be put on the system as part of children going back to school,” he said. “It’s going to be paramount that the turnaround time be relatively quick.”

Ontario Premier Doug Ford said he discussed testing with Canada’s Deputy Prime Minister Chrystia Freeland on Monday morning.

“All provinces, not just Ontario, are going to start ramping up for more testing,” he said.

Federal officials have said they are aiming for a “slow burn” of infection.

Dr. Irfan Dhalla, vice president of physician quality at Unity Health, which operates two hospitals in Toronto, has argued that the country should instead try to come as close as possible to eliminating the virus, following New Zealand and Canada’s own Atlantic provinces, with testing, tracing, isolation and support.

“It’s only a matter of time before we start seeing hospitalizations increase, and before we start seeing more people dying again,” said Dhalla.

Infections in Ontario, the most populous province, charged through the 300 mark on Monday, after dropping to below 100 a day in early August with the government blaming the spread on private social gatherings like weddings.

British Columbia, which imposed fresh curbs on nightclubs last week, reported its highest-ever case count of 139 on Sept. 10. Cases are also rising in Quebec, where classes resumed first.

Quebec teachers’ union Fédération autonome de l’enseignement (FAE) filed a lawsuit on Monday, seeking more information about a promised plan to ensure teachers and students have access to accelerated testing, and on the number of COVID-19 cases in schools.

“The government is currently giving the impression that it is improvising, while the virus doesn’t give second chances,” FAE president Sylvain Mallette said in a statement.

Prime Minister Justin Trudeau reiterated his message on Monday, asking people to remain vigilant: “The last thing anyone wants is to go into this fall and lock down, similar to this spring,” he said.

(Additional reporting by Mahad Arale in Toronto, Allison Lampert in Montreal and Steve Scherer in Ottawa; Editing by Andrea Ricci)