MONTREAL -- Ontario Premier Doug Ford is facing plenty of backlash in his own province for calling a 28-day lockdown across most regions.

But some in Quebec say the Ontario plan is an improvement on the one they've got lined up., which starts in just three days. 

Essentially, 28 days is going to be more effective at this point than 18 days, said Dr. Leighanne Parkes, a microbiologist based at the Jewish General Hospital.

"We are implementing it when we are at an exponential growth rate," she said Tuesday, after Quebec broke its third all-time daily COVID-19 record in four days.

Shutting down is undoubtedly a good idea, she said -- it's just not clear that 18 days will actually get the virus under control, as it's intended to do.

"This is just because of the nature of the virus," she said. 

We know that "people are contagious three days before onset of symptoms, that there can be a two-week incubation period and that sometimes the person who is the infector doesn't develop symptoms until after the person they infect," she said.

Ontario's 28-day plan is based on the idea that hospitals will still be overwhelmed with any shorter timeline than that.

"As much as I'd love to keep everyone open, health trumps that," Ford said. "I'm not ever going to ignore our docs, I'm just not going to do that."

Quebec Premier François Legault said this week that he was juggling a few factors.

"Of course the longer it is, the more efficient, is but we have to balance that with mental health with the economy," Legault said.

Another doctor said 18 days might just work.

"For the majority of people, the incubation period is between five and 10 days," said Dr. Donald Vinh, an infectious diseases specialist at the MUHC.

"So this means that a lockdown needs to be at least two times five, or 10," he explained.

"But really [it should be] more around two times ten or twenty days," to stop people from infecting others right at the end of their infection cycle.

"So 18 days is a fair compromise."

Legault also reminded people there's another kind of implicit bargain in the lockdown: if people follow the rules strictly, there won't be a need to extend it.