The Timeline of COVID-19 Variants
Posted at2022-10-14

The first-ever COVID-19 strain detected in Wuhan, China in December 2019 was called the L strain. No one really remembers it because the virus has quickly mutated into other strains since early 2020—and that was before any of us cared about COVID-19 variants.

At the time, China and some other countries in Asia that had experienced the 2003 SARS epidemic were on high alert. The Chinese government placed several cities on lockdown in January 2020, but the coronavirus was still creeping up on the United States then.

As COVID-19 started going through more drastic mutations, the World Health Organization decided to name each prominent variant using the Greek alphabet, starting with Alpha.

Here’s a list of the most significant variants, how they’ve changed the course of the pandemic, and the most reported symptoms.

Alpha (B.1.1.7)

By the end of 2020, the original L strain had gone through multiple mutations, including the S, V, G strains.

But the first highly publicized variant—Alpha (B.1.1.7)—appeared in the United Kingdom in September 2020. It caused a surge of infections around the world, starting before any coronavirus vaccines were available. This variant was more deadly than the original strain.1

Most common symptoms: The Alpha variant shared many of the reported symptoms as those from the original strain, including loss of taste or smell, fever, dry coughs, shortness of breath, headache, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea.

Beta (B.1.351)

Shortly after Alpha was discovered, the Beta variant (B.1.351) was identified in South Africa and spread to other countries. Although an estimate cited by the CDC suggested that the Beta variant was about 50% more transmissible than the original strain, it only ever accounted for a very small percentage of the overall cases in the U.S.

Gamma (P.1)

The Gamma variant was first identified in Brazil in November 2020. It was responsible for a fraction of the COVID-19 cases in the U.S. Although data on the Gamma variant was limited, experts said it wasn’t as transmissible as Alpha or Delta.2

Delta (B.1.617.2)

The Delta variant took the world by storm in 2021. It first became the dominant variant in India and spread to over 130 countries, causing a deadly wave of infections worldwide.3

Multiple studies showed that Delta caused more severe disease and hospitalizations in unvaccinated people than other variants.

Although the U.S. had already launched its COVID-19 vaccination campaign, the Delta variant managed to evade vaccine-induced immunity. In one small study, more than 70% of infections occurred in patients who were fully vaccinated.4

The surges prompted health authorities around the world to urge people to get a booster vaccine.

Most common symptoms: headache, sore throat, runny nose, fever

Delta AY.4.2 (Delta Plus)

Delta AY.4.2, also referred to as Delta Plus, was an offshoot of the Delta variant. Delta AY.4.2 had two mutations on its spike protein, which allows the virus to enter and infect cells. It was thought to be 10%-20% more transmissible than Delta.5

This variant was responsible for a surge in the U.K. but didn’t take hold in the U.S.

Omicron (BA.1)

The original Omicron variant was first identified in late November 2021 and overtook Delta as the dominant variant in a month. Although the highly mutated variant was extremely transmissible, some studies showed that it caused milder infections and people were less likely to be hospitalized.

Most common symptoms: headache, sore throat, runny nose, cough, fatigue6

Omicron BA.2

When Omicron subvariant BA.2 was first reported, the media dubbed it a “stealth” variant because it was hard to detect and track. The WHO said that BA.2 had a “growth advantage” over the original Omicron. It started growing in prevalence in northeastern U.S. around March 2022.

Most common symptoms: BA.2 symptoms were similar to those of BA.1

Omicron BA.2.12.1

An offshoot of the Omicron BA.2, the BA.2.12.21 variant accounted for a majority of the new cases in northeastern U.S. by May 2022. It contained about 20 of the same mutations seen in the original Omicron, and seven new ones. It was thought to be more transmissible than its predecessors, but the infection would largely remain in the upper respiratory tract instead of moving deeper into the lungs.

Omicron BA.4 and BA.5

Omicron BA.4 and BA.5 appeared in the U.S. around May 2022. Data suggested that these two subvariants can evade immune defenses better than earlier versions of Omicron, causing reinfections even in those who have received a booster shot or recently recovered from COVID.

In anticipation of another surge of infections, the FDA authorized Pfizer’s and Moderna’s bivalent booster shots in September 2022. The reformulated booster shot can target the original strain and the Omicron subvariants, including BA.4 and BA.5.

Most common symptoms: sore throat, cough, hoarse voice

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