WHO labelled COVID-19's four variants of concern (VOC) and six variants of interest (VOI) using Greek alphabets. For VOC, WHO named the variant first identified in UK as 'Alpha', variant first identified in South Africa as 'Beta', variant identified in Brazil as 'Gamma' and variant first identified in India as 'Delta'. Epsilon, Zeta, Eta, Theta, Iota and Kappa are VOI.