Highly contagious 'Kraken' subvariant becoming dominant in Ottawa, spreading exponentially throughout Ontario

Ottawa is at the start of a new COVID-19 wave fuelled by the so-called Kraken subvariant, according to one of the city’s leading wastewater researchers.

Tyson Graber, associate scientist at the CHEO Research Institute and co-lead investigator on Ottawa’s coronavirus wastewater monitoring program, says the highly contagious XBB.1.5 subvariant, nicknamed Kraken, is spreading “exponentially” across Ontario.

In Ottawa, it already represents between 30 and 50 per cent of the wastewater signal, which measures the amount of virus in the community through wastewater. Graber said the subvariant should make up the majority of COVID-19 infections within the city in the next week or so.

When an emerging variant reaches more than 50 per cent of the wastewater signal, cases typically begin to increase in the community, he said. “I think it is a foregone conclusion that we will see an increase in cases in the next few weeks.”

The start of the wave is already showing up in wastewater, he said. “We are in the XBB wave.”

Graber said he could not predict how big the wave would get.

The growth of XBB.1.5 in Ottawa comes at a time when cases have stabilized and decreased, but have not dropped significantly and people are continuing to die from COVID-19. In the past week, Ottawa Public Health has reported the deaths of seven people and has said levels of COVID-19 remain high, with 33 people in hospital with active infections and four people in intensive care units as of earlier this week. A total of 1,015 Ottawa residents have died since the pandemic began in March 2020.

The subvariant XBB.1.5 drew global attention late last year, when the World Health Organization deemed it the most contagious version of the Omicron variant to date and experts worried about its ability to evade immunity from past infections and some vaccines. Its rapid rise in the northeastern United States put the world on edge.

Graber conceded that initial concerns about XBB.1.5 were “probably a little overhyped.” It is the most contagious Omicron subvariant to date, gaining dominance over previous highly transmissible subvariants, but its growth has been slower than some predicted, he said.

And, while it appears to be more immune evasive than previous subvariants, there is no evidence it causes more severe disease in those infected compared to previous mutations of the SARS-CoV2 virus.

Still, high transmissibility results in more cases, which can mean more deaths.

Graber says there are reasons to be concerned about the growth of the contagious subvariant.

Ottawa, which was among the most highly vaccinated parts of Canada early in the pandemic, is seeing vaccination rates decline dramatically over time, something that is happening across Ontario.

Currently, just 31 per cent of Ottawa residents have received COVID-19 booster vaccines within the past six months. Nationally, about 25 per cent of people have either completed their primary series of vaccines or received booster doses within the past six months, the Public Health Agency of Canada says.

“More and more people are more than six months out from their last vaccine,” Graber said.

That waning immunity, combined with evasiveness, could make more people vulnerable as XBB.1.5 spreads.

Graber says anyone who has never been infected and is not vaccinated or has waning vaccine immunity is at risk of severe disease because it is so contagious.

Last month, Ontario’s Chief Medical Officer of Health, Dr. Kieran Moore, urged residents to remain vigilant as the Kraken subvariant began to increase around the province.

In a revised risk assessment for the sub-lineage XBB, which includes XBB.1 and XBB.1.5, Public Health Ontario said XBB was among the most immune-evasive SARS-CoV-2 variants, based on studies, as well as one of the most transmissible variants.

Public Health Ontario says it remains uncertain whether it causes more severe disease than previous variants, but COVID-19 bivalent mRNA vaccines provide additional protection against XBB.1.5-related infections.

Using layers of protection in addition to the vaccination, including staying home when sick, wearing well-fitted high-quality masks in indoor settings “where feasible,” optimizing indoor air quality and using outdoor spaces are all important to reduce risk, PHO wrote.

T Ryan Gregory, the University of Guelph evolutionary biologist and genome biologist who named the Kraken variant, says he doesn’t expect XBB.1.5 or any other single Omicron variant to cause a massive wave on its own, although he is wary that people might dismiss it.

Gregory says the issue is that cases never get very low after waves.

“It’s not tsunamis anymore,” Gregory said. “It’s rising sea level with high and low tide. XBB.1.5 is likely to cause another high tide, but not a tidal wave like BA.1 and BA.2 did.”