Like the other variants of concern, B.1.617 contains not just two mutations, but more than a dozen. That all said, there's a reason why the term "double mutant" came about. First, B.1.617 has a mutation (labeled L452R) that's also present in the dominant strain in California. Second, B.1.617 has a similar mutation (called E484Q) as the one present in the variants first detected in South Africa and Brazil (that mutation is called E484K). So in a nutshell, B.1.617 has two "famous" mutations. But it also has about 11 other ones as well. Preliminary evidence suggests that B1.617 is more contagious than previous strains of the virus. A study published Tuesday found that the L452R mutation may enhance the ability of viruses to infect human cells in the laboratory. The variant in California, which carries this same mutation, is about 20 percent more transmissible than older strains of the virus.