If a mutation has a previous association with a similar variant, which could have an impact on public health, it becomes a Variant under Investigation. When genetic markers, which can be associated with receptor binding domain or could have an implication on antibodies or neutralising assays are identified, it is called a Variant of Interest. It becomes a Variant of Concern once we get evidence of increased transmission from field-site and clinical correlations. Variants of Concern have one or more of these features: Increased transmissibility. Change in virulence/disease presentation. Ability to evade diagnostics, drugs, and vaccines. As of now, four variants of concern have been identified by scientists – Alpha, Beta, Gamma, and Delta.