The so-called FLiRT variants of SARS-CoV-2 coronavirus that cause COVID-19 have been the dominant forms of the virus circulating this year globally, according to the World Health Organization (WHO).

FLiRT is an acronym for the locations of the mutations the variants share on the virus' spike protein. One of them, called KP.3, has become the most commonly circulating variant in the United States over the past month, according to the U.S. Centers for Disease Control and Prevention (CDC).

Here is what you need to know about FLiRT.

The FLiRT variants, which also include KP.3's "parental" lineage JN.1, have three key mutations on their spike protein that could help them evade antibodies, according to Johns Hopkins University.

Are FLiRT variants more contagious or likely to cause more severe illness?

Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital in Oceanside, New York and a spokesperson for the Infectious Diseases Society of America said that he had not seen evidence of an uptick in disease or hospitalizations, based on the data he tracks and experience with his own patients.

"There have been some significant changes in the variants, but I think in recent times it's not been as important, probably because of the immunity many, many people already have" from prior illness and vaccination.

CDC data suggests that COVID-related hospitalizations have risen slightly since April and the number of patients in emergency departments who have tested positive for COVID has increased since May, in line with trends a year ago.

Do current vaccines work against the FLiRT variants?

The current vaccines should still have some benefit against the new variants, Glatt said.

Since 2022, health regulators have asked vaccine makers to design new versions of the COVID-19 vaccines to better target circulating variants.

Europe's regulator has said vaccine makers should target the JN.1 variant. U.S. regulators asked for the vaccines to target variants within the JN.1 lineage, but said the preferred strain to target would be the KP.2 strain, which was dominant in June.