First detected in India, Omicron subvariant XBB.1.16 - also known as "Arcturus" - has already been reported in over 30 countries. This is what we know about it so far.
XBB has been on the CDC’s radar since earlier this month, when it first began doubling its case counts every 12 days. It is a combination of two Omicron subvariants (BA.2.10.1 and BA.2.75) first seen in September and is among a growing group that could render some antibody treatments ineffective.