Health care officials are watching closely a new rapidly spreading Omicron subvariant.

The World Health Organization says the XBB.1.5 subvariant is the most transmissible version of COVID so far, but it’s still not known whether it makes people sicker.

Dalhousie University infectious disease specialist, physician and researcher Dr. Lisa Barrett says the subvariant emerged in the last few months.

Barrett says there are still lots of unknowns about the mutation, including whether or not previous infections or vaccines will help protect you.

She says it doesn’t appear to be more virulent than other strains and subvariants, but they still don’t know what its impact might be on long COVID and overall immunity over time.