Why do viruses change?
Viruses constantly change through mutation, and new variants of a virus are expected to occur. A variant has one or more mutations that differentiate it from other variants in circulation. As expected, multiple variants of SARS-CoV-2 have been documented in the United States and globally throughout this pandemic. To inform local outbreak investigations and understand national trends, scientists compare genetic differences between viruses to identify variants and how they are related to each other.
What is the Delta Variant?
To assist with public discussions of variants, the World Health Organization proposed using labels consisting of the Greek Alphabet, e.g., Alpha, Beta, Gamma, as a practical way to discuss variants by non-scientific audiences. Delta is the B.1.617.2 "mutant" strain originating in India. Delta is now the predominant strain (>80%) in the US. https://covid.cdc.gov/covid-data-tracker/#variant-proportions
What are the variants currently in the United States?
Multiple variants are being monitored. Currently there are four notable variants in the United States:
- B.1.1.7 (Alpha): This variant was first detected in the United States in December 2020. It was initially detected in the United Kingdom.
- B.1.351 (Beta): This variant was first detected in the United States at the end of January 2021. It was initially detected in South Africa in December 2020.
- P.1 (Gamma): This variant was first detected in the United States in January 2021. P.1 was initially identified in travelers from Brazil, who were tested during routine screening at an airport in Japan, in early January.
- B.1.617.2 (Delta): This variant was first detected in the United States in March 2021. It was initially identified in India in December 2020.
These variants seem to spread more easily and quickly than other variants, which may lead to more cases of COVID-19. An increase in the number of cases will put more strain on healthcare resources, lead to more hospitalizations, and potentially more deaths.
So far, studies suggest that the current authorized vaccines work on the circulating variants. Scientists will continue to study these and other variants.
How is the Delta variant different?
The Delta variant is more contagious than other variants and it is more able to be spread by vaccinated individuals. Delta may cause more serious disease. People who have not been fully vaccinated against COVID-19 are most at risk.