The World Health Organization (WHO) has classified a new Covid-19 coronavirus subvariant, XBB.1.16, as a variant under monitoring (VUM). While not as serious as a variant of interest (VOI) or a variant of concern (VOC), the spread of XBB.1.16 has fueled a surge in Covid-19 cases in India and has prompted the reintroduction of face mask mandates. The subvariant has a growth advantage over other SARS-CoV-2 variants and subvariants, and has gone from accounting for 0.21% of all Covid-19 cases worldwide in late February to an estimated 3.96% a month later. In the US, it accounted for an estimated 7.2% of all Covid-19 samples from April 9 to April 15. While XBB.1.5 remains the dominant variant in the US, the XBB.1.16 has overtaken other subvariants to reach second place.
The WHO has categorized XBB.1.16 as a VUM, which is defined as having genetic changes that affect virus characteristics and early signals of growth advantage relative to other circulating variants, but for which evidence of phenotypic or epidemiological impact remains unclear. The subvariant has already appeared in at least 29 countries, and it is unclear whether it will cause more severe Covid-19 than other existing variants and subvariants. There have been anecdotes of conjunctivitis symptoms associated with XBB.1.16 infections, but it is not yet clear how common these symptoms are or what other symptoms and problems may emerge.
While political leaders may want to downplay the threat of Covid-19, the virus has not gone away and it is important to keep track of emerging variants and subvariants. XBB.1.16 bears close watching, and it remains to be seen what impact it will have.