BA.4 is here: What does this mean for Alberta's COVID trajectory?
Dr. Deena Hinshaw announced Alberta's first identified case of the Omicron subvariant on Wednesday
The Omicron subvariant BA.4 has officially arrived in Alberta, and while doctors and scientists expect it will likely trigger an uptick in cases, it is unclear just how dramatic that surge will be or whether it will put further strain on hospitals.
Alberta's chief medical officer of health, Dr. Deena Hinshaw, announced on Wednesday that a single case of the subvariant, which was first identified in South Africa and has since been detected in other countries, has been discovered through ongoing surveillance.
The BA.4 case was found in a sample collected in early May.
"This is not really surprising news," said Craig Jenne, an associate professor of microbiology, immunology and infectious diseases at the University of Calgary.
"We've known that this variant has been circulating for a while now and really with open travel now...the concept of keeping these international and even inter-provincial variants out of Alberta really is not possible."
According to Jenne, BA.4 appears to be more infectious, which means it can spread further and faster. But so far, there are no signs it causes more severe disease.
"It does change the landscape a little bit, but very much in a way that was expected to happen."
The big question now, he says, is whether or not BA.4 will lead to a small uptick in cases or a larger wave.
"If this simply leads to more breakthrough infections but no increased risk of hospitalization, we may see a very small effect from these new variants in the province. If however, those breakthrough infections do lead to large numbers of cases and as a result — even if its a small percentage — larger numbers of people going to the hospital, that will unfortunately dramatically affect our response and the concept of future waves here in the province."
With Alberta's limited PCR testing it's difficult to know how much of a foothold BA.4 may already have in the province.
"In addition to it likely being here before this actual detection, we are probably underestimating it. When the vast majority of cases in the province are no longer PCR tested, it does provide the opportunity for variants to enter and circulate through the province," says Jenne.
"So although surveillance can pick it up, we still don't know how far it has spread or when it first arrived in Alberta."
More cases likely out there
Dr. Stephanie Smith, an infectious disease physician at the University of Alberta hospital, expects there are likely more cases in the province that have simply gone undetected.
"We've identified this one case. I suspect there's more and certainly if there's any kind of advantage with BA.4 — which it does seem to have an advantage over our previous BA.2 — then it will become the predominant strain eventually," she said, adding it will take a few months for the new subvariant to displace the old one.
Smith also expects BA.4 will drive an uptick in cases.
However, she said immunity from both natural infections and vaccines will likely offer protection against a large jump in the number of severely ill patients.
"I think we probably won't see a huge increase in hospitalizations related to that...What we tend to see is that these surges keep getting smaller. And I expect that we may see some slight increase in community spread, but we do not anticipate that we will see huge numbers in hospitalizations."
The provincial lab is currently screening all positive PCR tests for variants of concern, including Omicron sublineages.
All potential cases of BA.4 that are flagged through that process are sent on for confirmation through full genome sequencing. That process takes two to three weeks.