A new  coronavirus  subvariant, XBB. 1.16, has been designated as a “variant under monitoring” by the World Health Organization. The latest omicron offshoot is particularly prevalent in India, where it has sparked a rise in infections, and a return to mask mandates in parts of the country.

Here’s what you need to know about the subvariant called Arcturus, which has been documented in 29 countries so far.

Arcturus  was first detected  in a sample from January and has now been documented in 29 countries, according to  the World Health Organization . It is a subvariant of the omicron variant, which  emerged in late 2021  and replaced delta as the dominant variant around the world.

By late February, the Arcturus strain accounted for 0.21 percent of cases around the world. A month later, this had risen to 3.96 percent, according to WHO figures. In the United States,  it is estimated to account for 7.2 percent of coronavirus infections  for the week ending April 15, according to the Centers for Disease Control and Prevention.

The WHO  designated  XBB. 1.16 a “variant under monitoring” on March 22. This means the variant has “genetic changes” that could affect its characteristics as a virus, including a possible “growth advantage” over other variants, but the epidemiological impact is not clear. The WHO is monitoring seven variants, including the BA.2 version of omicron seen in many parts of the United States.

A “variant under monitoring” is considered to be of lesser concern than a “variant of interest,” which is predicted or known to be more transmissible or virulent, or able to evade antibodies, according to the WHO. The XBB. 1.5 strain, currently the most prevalent subvariant globally, is described as a variant of interest.