Worried that new variants of the novel coronavirus may be spreading more easily between household members, Alberta will now require some close contacts of COVID-19 patients to spend 24 days or more in quarantine.

The new rule, which will leave some Albertans with the longest mandatory quarantine period in Canada, was announced Tuesday by Dr. Deena Hinshaw, the province's chief medical officer of health.

Federally, the Public Health Agency of Canada requires that individuals quarantine for 14 days if they have had close contact with a COVID-19 patient, are returning from outside the country or have been told to do so by public health authorities, even if they have not tested positive for the virus and do not have any symptoms of it.

In Alberta, as in most of the country, the 14-day period has until now started immediately after a close contact's first exposure. In other words, if somebody tested positive for the virus today, everyone else in their household would have to stay home for the next two weeks.

The problem with that, Hinshaw said, is the mounting evidence that at least some of the new variants can help the virus spread more easily between people.

The new requirement addresses this by moving the start of the 14-day quarantine to the end of the patient's isolation period, which lasts for 10 days – or longer, if symptoms persist -- for household members of variant patients only.

"If cases choose to stay at home during their isolation period, their household contacts will now need to stay at home as well in quarantine until 14 days have passed from the case's isolation period, for a total of 24 days," Hinshaw said at a press briefing.

"We will no longer assess the ability to stay in a different part of the house as adequate for isolation."

WHAT'S BEHIND THIS?

The 24-day quarantine applies only to household members of patients who test positive for what Hinshaw described as "variants of concern." As of Tuesday, 50 cases of the B.1.1.7 variant first identified in the United Kingdom had been detected in Alberta, as well as seven cases of the B.1.351 variant first identified in South Africa.

"Given how easily this variant is spreading in homes, this enhancement is necessary to prevent spread in the community," Hinshaw said.

Dr. Sumon Chakrabarti, an infectious diseases specialist at Trillium Health Partners in Mississauga, Ont., said Wednesday that he hopes other provinces will be "very, very careful" about adopting similar measures.

He questioned whether everyone will follow the new rule, given that it means more than three weeks of not leaving the house even for those who never show COVID-19 symptoms or test positive for it themselves.

"You can make a recommendation, but if people don't follow it, then that's worse than no recommendation at all," he said.

Alberta also offers free hotel rooms for COVID-19 patients, allowing them to spend their isolation periods away from their home, which in turn removes the requirement for those they live with to self-isolate.

Chakrabarti said the longer quarantine period might be a deterrent measure, designed to discourage at-home isolation in favour of hotel stays.

"Household transmission, as we know, is one of the biggest [methods] of transmission, because that's who you spend the most time with," he said.

"Even though people say 'OK, look, I'm isolating, my dad is going to be staying in the basement' … I think what they're assuming is that people are not going to do it properly."

VARIANT SPREAD STATUS REPORT

More than 80 per cent of those who have tested positive for COVID-19 variants in Alberta have either travelled outside Canada or have had close exposure with someone else who travelled, Hinshaw said.  That travel has involved "many different countries," she said, not just the nations most identified with the variants.

Eight cases across five households have no known contact with travellers; four of the eight are linked to one daycare facility.

Dr. Zain Chagla, an infectious disease specialist affiliated with McMaster University in Hamilton, told CTV News Channel on Tuesday that, while the world is mostly focused right now on B.1.1.7, B.1.351 and the P.1 lineage variant first identified in Brazil, further mutations are likely.

"As many of these mutations emerge, they seem to have the same patterns, and we may see more in the days to come," he said.

Other SARS-CoV-2 variants may already be circulating, he said, undetected because of a lack of ability to recognize them and test for them in some parts of the world.

Chakrabarti said the key is to recognize that once new strains of the virus reach the community spread stage, they will hit hardest in the same places that see the most spread of the virus in general, including long-term care homes and essential workplaces.

"This is an impetus for us to go all there and really … bolster and fortify our public health protocols in those high-risk areas as much as we can," he said.