MONTREAL — Three Quebec cabinet ministers and Montreal Mayor Valerie Plante are self-isolating after a suburban mayor contracted COVID-19.

Justice Minister Simon Jolin-Barrette, Transport Minister Francois Bonnardel and Chantal Rouleau, the minister responsible for the Montreal region, have been placed in isolation after learning Longueuil Mayor Sylvie Parent tested positive for the novel coronavirus.

All three ministers and members of their staff met with Parent last week and were to be tested Tuesday for COVID-19.

Plante says she had not met with Parent but did meet with Rouleau in the last few days.

"I will put myself, as a precaution, in preventive isolation until Ms. Rouleau's test results are known," Plante tweeted.

National assembly members Ian Lafreniere and Catherine Fournier and Laval Mayor Marc Demers also said they will self-isolate and get tested after attending events last week where Parent was present.

The news came as the province introduced a regional alert system in the hopes of stifling a potential second wave of the novel coronavirus.

Provincial Health Minister Christian Dube unveiled the four-level, colour-coded system Tuesday. The levels are green for vigilance, yellow for an early warning, orange for moderate alert and red for maximum alert.

"We are observing an increase in public (outbreaks)," Dube told a news conference in Montreal. "I repeat, health instructions need to be followed. Each and every one can make a big, big difference in containing the virus."

The levels carry different measures to be enacted depending on the status of an outbreak, including reducing the number of people in private gatherings, restricting travel between regions and curtailing commercial activities.

Dube stressed that approaches will be different for each region and that "temporary measures" could be enacted in specific areas, depending on transmission.

Health officials been evaluating different Quebec regions since the week of Aug. 15. Four regions — Quebec City, Laval, Outaouais and Estrie — are at the early warning, or yellow, level, Dube said.

Montreal is currently at green after entering the yellow level last month.

"The virus is present. It's a traitor, it will stab us in the back," public health director Horacio Arruda warned. "So we need these levels."

Meanwhile, the Quebec government says up to 120 schools may have already been affected by COVID-19 since classes began last week.

The government released a list of schools that have either confirmed or potential cases of the novel coronavirus among students and staff.

Seventy schools had recorded at least one case as of the end of day Friday, ranging from elementary through high school.

Another 50 schools, including 19 in the Montreal area, are listed as having potential cases. The government says these schools will need to be verified because the information was not transmitted through the established process.

Education Minister Jean-Francois Roberge told a news conference in Quebec City that there have been 118 confirmed COVID-19 cases among teachers and students since classes resumed.

Roberge said the numbers need to be put in perspective. "When we talk about 120 schools possibly affected, that's out of a total of 3,100, and when we talk about 118 people, that's out of 1.4 million," he said.

Quebec health authorities reported 163 new cases of COVID-19 across the province Tuesday and no additional deaths. Previously, the province had seen two straight days with more than 200 new cases of the novel coronavirus.

The number of hospitalizations related to the virus remains at 105, while the number of patients in intensive care has dropped to 15.

Quebec has now seen 63,876 cases of COVID-19 and 5,770 deaths since the pandemic began.

This article by The Canadian Press was first published Sept. 8, 2020.

— With files from Caroline Plante in Quebec City

Julian McKenzie, The Canadian Press