New SARS-CoV-2 variant strains continue to emerge as the virus spreads globally. Here is a breakdown of omicron sublineages and recombinant strains that have made headlines in recent weeks and months.
BA.2
BA.2 is currently the dominant variant circulating globally, according to the World Health Organization. The subvariant accounted for 74.4 percent of all cases in the U.S. for the week ending April 16, according to the latest CDC estimates.
First identified: November 2021 in South Africa
Disease severity: There is no evidence to suggest it causes more severe illness than BA.1, the original omicron variant.
Transmissibility: Studies have shown the strain has a growth advantage over BA.1, according to the WHO. In March, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told ABC News the subvariant was about 50 percent to 60 percent more transmissible than omicron. Initial data from population-level reinfection studies have suggested infection with BA.1 provides strong protection against reinfection from this strain.
Ability to evade vaccines: BA.2 does not seem to evade immune responses from vaccination or prior infection, Dr. Fauci said. Studies have shown vaccination offered strong protection against hospitalization caused by BA.2.
BA.2.12 and BA.2.12.1
These two sublineages of BA.2 have recently made headlines for their rising prevalence in the U.S. Notably, health officials in New York estimated the sublineages collectively accounted for more than 90 percent of cases as of April 13.
Disease severity: There hasn't been evidence to suggest the sublineages cause more severe illness.
Transmissibility: The strains are estimated to have a 23 percent to 27 percent growth advantage over BA.2, respectively.
Countries with confirmed cases, as of April 14: U.S., Canada, United Kingdom, Australia, Israel and Luxembourg, according to NPR.
Ability to evade vaccines: Not enough evidence to draw conclusions
BA.4 and BA.5
The WHO on April 11 said it is monitoring two new "sister variants" of the original omicron strain dubbed BA.4 and BA.5.
First identified: South Africa (Jan. 10 for BA.4 and Feb. 25 for BA.5)
Countries with confirmed cases:
- BA.4: South Africa (41 cases as of April 8), Denmark (3), Botswana (2), England (1) and Scotland (1)
- BA.5: South Africa (27 cases as of March 25)
Disease severity: Not enough evidence to draw conclusions
Transmissibility: Not enough evidence to draw conclusions
Ability to evade vaccines: Not enough evidence to draw conclusions
Deltacron
Deltacron is a recombinant virus, meaning it comprises genetic materials from two distinct virus strains: delta (AY.4) and omicron (BA.1).
First identified: France in January
Countries with confirmed cases, as of April 26: France (75), Denmark (8), Germany (1), Netherlands (1) and Belgium (1), according to GISAID, a global data-sharing platform for viruses.
Disease severity: Not enough evidence to draw conclusions
Transmissibility: Not enough evidence to draw conclusions
Ability to evade vaccines: Not enough evidence to draw conclusions
Omicron XE
Omicron XE is a recombinant variant that's a hybrid of BA.1, the original omicron strain, and BA.2.
First identified: Jan. 19 in the U.K.
Countries with confirmed cases, as of April 12: Britain, Japan, Thailand, India and Israel, according to CNBC.
Disease severity: Not enough evidence to draw conclusions
Transmissibility: Initial estimates suggest XE is 10 percent more transmissible than BA.2, though more research is needed to confirm this finding, according to the WHO.
Ability to evade vaccines: Not enough evidence to draw conclusions