How mutations shaped the Covid-19 pandemic – .


Based on a recent government projection, the Delta variant of the Covid-19 virus could become the dominant type of this coronavirus in the United States within a month, making it one of the more aggressive variants in s ‘settle in the country.

Delta is the latest in a series of variants that have spread to the United States. Like all viruses, coronaviruses mutate as they reproduce. Some of these genetic changes make them better able to infect human cells or escape our immune system. As new, better-suited variants emerge, they push back earlier versions of the virus. Here’s a look at how this process has unfolded in the United States since the start of the pandemic.


Derived from the ancestral version of the Covid-19 virus that was first detected in China, the A.1 lineage is associated with some of the first cases of Covid-19 in the United States, including the epidemic in the Washington State which was first detected in January 2020. Its number has declined as other variants have taken hold in the country.

Prevalence of coronavirus lineages / variants in the United States

Prevalence of coronavirus lineages / variants in the United States

Prevalence of coronavirus lineages / variants in the United States


Associated with the outbreak in early 2020 in northern Italy, the virus developed a mutation called D614G, which helped it infect cells better, allowing it to supplant earlier variants. The B.1 lineage has become the dominant version both globally and in the United States


Derived from B.1, the B.1.2 variant came to represent more than 40% of US samples of the new coronavirus at the end of last year, as it spread rapidly in the South and the Southwest. Since then, its prevalence has steadily declined.

Regional variants: Epsilon and Iota

As cases of Covid-19 in the United States reached new highs last winter, scientists have detected the increased presence of two variants in New York and California.

The variants are now called Epsilon (for California) and Iota (for New York). The World Health Organization has started naming major variants with letters of the Greek alphabet to de-stigmatize countries where they were first detected.


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The Epsilon variant was first identified in California in January. It has a mutation called L452R, which can make it more efficient at infecting cells. Studies suggest that Epsilon is about 20% more transmissible than early versions of the virus. As of February, the variant accounted for 15% of samples nationwide.

The Iota variant began to circulate in New York in November. It has a mutation called E484K, which can help it escape the body’s immune system. In April, Iota accounted for 40% of positive Covid-19 tests in New York City and 15% of samples nationwide.


First detected in December in the UK, the Alpha variant combines an arsenal of mutations that help make it around 50% more transmissible than early versions of the virus. One of them, P681H, can facilitate the entry of the virus into cells. Alpha reached the United States in January. By March, he had ruled out other variants to become the dominant type nationally.

Delta variant

The variant was first detected in India last October, where it helped fuel a devastating wave of Covid-19 that has set records for new infections and deaths. Delta has several of the mutations found in other variants, as well as related mutations affecting the same stretches of genetic code. Researchers believe it’s about 60% more transmissible than the Alpha variant.

The variant has spread to more than 70 countries.

Based on genome samples, Delta overtakes Alpha in the US From the last week of May to the second week of June, the prevalence of Delta nearly tripled while that of Alpha fell by about a quarter.

As Delta expands its presence in the United States, its potential impact on public health remains unclear. Studies suggest that Pfizer and AstraZeneca vaccines help reduce hospitalization rates in patients infected with the variant. But with less than half of the country fully vaccinated, many could still be at risk, especially in parts of the South where vaccination rates are low.

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