Viruses are always changing, and that can cause a new variant, or strain, of a virus to form. Although a variant usually doesn’t affect how the virus works, sometimes they make it act in different ways. Coronavirus disease (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus. A number of variants of the SARS-CoV-2 virus, including alpha, beta, gamma, delta and omicron, have been identified and characterized.

Variants are classified into different categories based on their genetic changes and potential impact on public health. These classifications often include terms like “variants of interest,” “variants of concern,” or “variants of high consequence.” Health authorities such as the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) regularly update these classifications based on emerging evidence. Next-generation sequencing (NGS) provides an effective, unbiased way to identify new coronavirus strains and other pathogens without prior knowledge of organisms.