All viruses, including SARS-CoV-2, the virus that causes COVID-19, change over time. Most changes have little to no impact on the virus’ properties. However, some changes may affect the virus’s properties, such as how easily it spreads, the associated disease severity, or the performance of vaccines, therapeutic medicines, diagnostic tools, or other public health and social measures. 

WHO, in collaboration with partners, expert networks, national authorities, institutions and researchers have been monitoring and assessing the evolution of SARS-CoV-2 since January 2020. During late 2020, the emergence of variants that posed an increased risk to global public health prompted the characterisation of specific Variants of Interest (VOIs) and Variants of Concern (VOCs), in order to prioritise global monitoring and research, and ultimately to inform the ongoing response to the COVID-19 pandemic.  

WHO and its international networks of experts are monitoring changes to the virus so that if significant mutations are identified, we can inform countries and the public about any changes needed to react to the variant, and prevent its spread. Globally, systems have been established and are being strengthened to detect “signals” of potential VOIs or VOCs and assess these based on the risk posed to global public health. National authorities may choose to designate other variants of local interest/concern. 

Current strategies and measures recommended by WHO continue to work against virus variants identified since the start of the pandemic. 

Naming SARS-CoV-2 variants

The established nomenclature systems for naming and tracking SARS-CoV-2 genetic lineages by GISAID, Nextstrain and Pango are currently and will remain in use by scientists and in scientific research. To assist with public discussions of variants, WHO convened a group of scientists from the WHO Virus Evolution Working Group, the WHO COVID-19 reference laboratory network, representatives from GISAID, Nextstrain, Pango and additional experts in virological, microbial nomenclature and communication from several countries and agencies to consider easy-to-pronounce and non-stigmatising labels for VOI and VOC. At the present time, this expert group convened by WHO has recommended using labeled using letters of the Greek Alphabet, i.e., Alpha, Beta, Gamma, which will be easier and more practical to discussed by non-scientific audiences. 

SARS-CoV-2 Variants of Concern and Variants of Interest, updated 31 May 2021

Variants of Concern 

A SARS-CoV-2 variant that meets the definition of a VOI (see below) and, through a comparative assessment, has been demonstrated to be associated with one or more of the following changes at a degree of global public health significance: 

• Increase in transmissibility or detrimental change in COVID-19 epidemiology; or 
• Increase in virulence or change in clinical disease presentation; or 
• Decrease in effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics.  

Variants of Interest 

A SARS-CoV-2 isolate is a Variant of Interest (VOI) if, compared to a reference isolate, its genome has mutations with established or suspected phenotypic implications, and either:  

• has been identified to cause community transmission/multiple COVID-19 cases/clusters, or has been detected in multiple countries; OR  
• is otherwise assessed to be a VOI by WHO in consultation with the WHO SARS-CoV-2 Virus Evolution Working Group.