The US Centers for Disease Control and Prevention has classified the Delta, a highly transmissible Covid-19 variant first identified in India, as a "variant of concern."
The CDC said the Delta variant shows increased transmissibility, potential reduction in neutralisation by some monoclonal antibody treatments. It also shows potential reduction in neutralization from sera after vaccination in lab tests.
A particular Covid-19 variant is only dubbed 'variant of concern' when scientists believe that coronavirus strain is shows increased transmissibility and a chance to cause more severe disease.
Vaccines, treatments, and tests that detect the virus may also be less effective against a variant of concern.
The Delta variant, which was dubbed a 'variant of concern' by the WHO on May 10, accounts for around 9.9% of all Covid-19 cases in the United States, the CDC estimates.