The Quebec Institute of Public Health (INSPQ) is recommending the COVID-19 Mu variant and its sublineage be included on the SARS-CoV-2 variants of interest list.

"Due to the international health situation, the recent increase in the number of cases of the lineage B.1.621 (Mu) in Quebec and its classification as a variant of interest (VoI) by several agencies... the INSPQ recommends that variant B.1.621 (Mu) and its sublineage be included in the list of SARS-CoV-2 in Quebec," a report from the INSPQ reads.

The Public Health Agency of Canada already lists Mu as a variant of interest, but not as a variant of concern (VoC).

The VoC list currently includes the Alpha, Beta, Gamma and Delta variants.

Dr. Donald Vinh said Detla remains the dominant variant and the one health agencies are most concerned about.

"Nobody should panic," said Vinh. "The reason it's of interest is that it is the appropriate location for this... For the moment, we just need to keep an eye on it, and we difinitely don't or should not be pannicking."

Mu cases have been detected in B.C. and Ontario and the first case in Quebec Mu was identified on May 18. The INSPQ confirmed 156 cases as of Sept. 16.

"It should be noted that the delays intrinsic to whole genome sequencing analyses certainly cause an underestimation of the number of cases of this lineage and its sublineage," the INSPQ said.

The INSPQ said in its report that due to the established criteria defining a variant of interest, Quebec should add Mu to the list.

When a variant is classified as such, it can be reported to the regional public health authorities and can be included in the regularly released statistics.

The Mu Variant Report from the data aggregating site Outbreak.info says that worldwide there were Mu 9,773 mu variant cases (7,279: B.1.621 and 2,494: B.1.621.1) as of Sept. 24.

A World Health Organization statement on booster doses said variants could be a reason to introduce booster doses of COVID-19 vaccine, though it adds, "To date, the evidence remains limited and still inconclusive on any widespread need for booster doses following a primary vaccination series."

The INSPQ cites a study saying the Mu variant was 7.6 times more resistant to the Pfizer-BioNtech vaccine than the original strain of the virus and more resistant to the vaccine than the other variants, including Delta.

"It's not clear right now what's going to happen with the Mu variant," said Vinh. "Is it going to fizzle out and go into extinction? Is it going to lead to itself or its descendants, becoming a predominant variant, it's not entirely clear."