There are many variants of coronavirus, each of which acts in a slightly different way than the one before or after.
“As viruses like SARS-CoV-2 cause infection, they replicate millions of times,” says Dr. Keith Armitage, professor of medicine in the division of infectious diseases at Case Western Reserve University and medical director of University Hospital Health System’s Roe Green Center for Travel Medicine and Global Health. “If you think about millions of people being infected, the virus has probably replicated billions of times.”
Of the variants, the Delta variant poses the most serious threat by far, but there have been others that have made a big impact.
“There is a concern that there could be a variant with an altered spike protein that could escape the vaccine or escape natural immunity,” says Armitage. “This is somewhat unlikely, as the spike protein is so important for the function of the virus [that] a significant mutation may make it nonviable. But there is a concern we could have a variant for which the current vaccines were not that effective.”
Here’s our breakdown of each of the coronavirus variants so far.
Origin: United Kingdom
How It’s Spread: Until the emergence of the Delta variant, the Alpha was the most prominent type throughout the world. It’s present in at least 114 countries. This variant spreads more easily and quickly than the original virus — to the tune of 30-50% increased transmissibility.
Treatment: Vaccines, including Pfizer-BioNTech, Moderna, AstraZeneca-Oxford, Johnson and Johnson, and Novavax, have shown to be effective against the alpha variant. Monoclonal antibody-based therapy has also shown efficacy.
Notable Fact: “The first variant that was in the news was Alpha,” says Armitage. “It seemed a little more contagious than the original wild type, but it’s been outstripped by Delta.”
Origin: South Africa
How It’s Spread: Beta has been detected in at least 48 countries and 23 U.S. states. In South Africa, in-hospital mortality due to Beta was 20% higher than the first wave of COVID-19.
Treatment: Vaccines appear to have decreased efficacy against the Beta variant. In fact, an AstraZeneca clinical trial was halted after it showed it was not effective against mild and moderate illness. Antibody therapy, too, appears to be less effective.
Notable Fact: “Beta seemed to cause maybe more severe illness in South Africa and was associated with a wave of infections there and may be more contagious,” says Armitage. “But, where Beta had established a foothold, once Delta got there, Beta faded.”
How It’s Spread: Gamma appears to be up to 2 1/2 times more transmissible than previous variants, but scientists have not yet determined whether it’s more lethal.
Treatment: Vaccines may be up to 50% less effective against the Gamma variant than earlier ones.
Notable Fact: “When Gamma was first detected in Brazil, there was concern it was infecting people who had previously been infected and it would cause a global wave,” Armitage says. “This has not happened.”
How It’s Spread: Delta appears to be twice as transmissible as previous variants and is detectable four days after exposure, as compared to a six-day average for previous variants. Delta is in 130 countries and the cause of 80% of new COVID-19 cases in the U.S. and up to 90% of new cases in the U.K. The viral load associated with Delta is up to 1,260 times higher than original virus.
Treatment: Vaccines are incredibly effective at preventing serious illness and death. Breakthrough cases (a COVID-19 diagnosis in a person who has been fully vaccinated) tend to be mild.
Notable Fact: “Wherever delta establishes a foothold, it takes over as the dominant variant,” says Armitage. “Experts like to say that Delta is so contagious, if you’re not immune, it’s going to find you.”
How It’s Spread: This variant has been detected in more than 39 countries, with 2,000 cases in the U.S.
Treatment: The efficacy of vaccines against this variant is unclear. It may be able to evade certain antibodies, including ones in vaccines.
Notable Fact: “Some early reporting from Brazil indicated that Mu might be more severe, but it hasn’t materialized as a global threat the same way Delta has,” Armitage says. “Mu is still a variant of interest, but I don’t think we know enough.”