MONTREAL -- Quebec health authorities trying to trace back the current COVID-19 outbreak on the South Shore are going to find social media a useful tool.

One girl acknowledged on Facebook that she threw a house party in Saint-Chrysostome, about 45 minutes from the South Shore, and that one guest had already tested positive for COVID-19 before coming to the party.

“Yes it was stupid, I know,” she wrote, about the decision to have the party.

Public health authorities now say some people infected with the virus who visited the Mile Public House in Brossard this weekend had been at two private parties in the area, which attracted 60 people between the two of them.

Twenty of those partygoers have now tested positive.

More posts and pictures showed what played out at the Mile Public House as those COVID-infected people mingled with others.

A photo taken overnight Saturday shows a lot of young people waiting in line close together and crowding inside, flouting laws about staying distanced.

It all led to stern warnings today from public health authorities, who said they won’t hesitate to close down bars again if patrons and owners don’t respect the rules.

However, it’s not as easy as it sounds to keep bars open while enforcing new habits inside, said infectious diseases specialist Dr. Matthew Oughton.

“Bars are meant for people to interact closely, have a good time, talk, drink, dance, sing, smoke, et cetera,” he said. 

“A lot of these activities are things that, unfortunately, do not go well with reducing risk of transmission.”

Yesterday, one day after pubs in the UK reopened, police there concluded that “drunk people can’t [or] won’t socially distance.”

Oughton said bar visits need to be done with masks on and frequent handwashing.

Starting in three weeks, wearing masks indoors will be mandatory in Montreal, Mayor Valerie Plante announced Monday, partly in response to the South Shore outbreak.