The B.1.621 Mu variant of COVID-19 was detected in Los Angeles for the first time last week, with 167 known cases being discovered by the Los Angeles County Department of Public Health.
"These specimens were sequenced between June 19 and August 21, with the majority of Mu specimens sequenced in July," public health officials said in a statement.
There have been 2,000 reported cases of the Mu variant in the United States, according to the Washington Post.
"This variant has a constellation of mutations that suggests that it would evade certain antibodies, not only monoclonal antibodies but vaccine and convalescent serum-induced antibodies," said Dr. Anthony Fauci in a video posted by the Washington Post. "But there isn't a lot of clinical data to suggest that. It is mostly laboratory in-vitro data.
"We're keeping a very close eye on it," he added. "It is really seen here, but it is not at all even close to being dominant."
The World Health Organization (WHO) designated the Mu variant, which was discovered in Colombia in January, as a "variant of interest" last week, saying that more study needs to be done to see if it could evade certain antibodies.
So far, the Mu variant has been discovered in some 40 countries including the UK, US, Hong Kong, South America and Europe, while the Delta variant spreads through the world including the US and Israel.