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SARS-CoV-2 Variants
Last updated on Oct 24, 2023Omicron XBB
XBB, a recombinant of the BA.2.10.1 and BA.2.75 sublineages, is an Omicron subvariant first detected in August 2022.
Links: Wikipedia
Omicron BA.4/5
On 4 May 2022, WHO Director-General Tedros Adhanom Ghebreyesus said South Africa reported two Omicron subtypes BA.4 and BA.5, which contributed to the surge in cases in South Africa.
Omicron BA.2
BA.2 was first detected in a sample from 15 November 2021.A preprint released in February 2022 (published in May) suggested that BA.2 was more transmissible than BA.1 and may cause more severe disease.
Links: Wikipedia
Omicron BA.1
Compared to wild-type viruses, the Spike region of the original Omicron-BA.1 genome had 35 mutations, including 30 amino acid replacements, 3 deletions and 3 amino acid insertions. Fifteen of these mutations are located in the receptor-binding domain (RBD) so they are clinically important. Studies and preliminary data on mutation sites suggest that Omicron spreads faster and evades antibodies more easily than previous variants, increasing the chances of reinfection in immunized people.
Omicron
On November 26, WHO classified the COVID-19 Omicron variant (B.1.1.529) as a variant of concern (VOC). South Africa was the first country to report the Omicron variant to the WHO, but a Dutch health agency confirmed that the variant was already present in the Netherlands a week earlier. In December 2021, a Japanese research team found that Omicron was 4.2 times more contagious than the Delta variant in its early stages. On 4 January 2022, the WHO has reported that the Omicron variant now spread to at least 128 countries worldwide. In February, the Omicron variant replaced the Delta variant as the main epidemic strain worldwide, and 98.3% of the new coronavirus genetic sequences reported were Omicron variant.
Alpha
B.1.1.7 was initially found in the United Kingdom in September 2020, which has now spread to at least 164 countries worldwide. The Alpha variant has been found to be at least 50% more contagious than the original COVID-19 virus. However, in a study published in April 2021, Alpha variant was not found to be associated with an increased risk of symptoms, severe disease, or death. The WHO has reported that vaccines from Pfizer/BioNTech , Moderna, and Novavax continue to be highly effective against the Alpha variant.
Beta
B.1.351 was initially discovered in South Africa in December 2020, which has now spread to at least 115 countries worldwide. The Centers for Disease Control and Prevention (CDC) estimates a 50% increased transmission rate of COVID-19 from the Beta variant. There is evidence about hospitalization and severity showing that there was an increase in mortality rate with the Beta variant. The WHO has reported that the Beta variant does cause a decrease in the effectiveness of vaccines. For example, the Johnson & Johnson vaccine has shown to be 85% effective.
Gamma
P.1 was discovered in four travelers from Brazil as they were screened at an airport in Japan in January 2021, which has now spread to at least 68 countries worldwide as of June 29, 2021. Recent studies did uncover that specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by the Gamma variant. The WHO has reported that the Gamma variant may cause a mild decrease in the effectiveness of vaccines, with studies still ongoing.
Delta
B.1.617.2 was initially discovered in India in December 2020, which has become the dominant strain globally until the worldwide surge of the Omicron variant (B.1.1.529) in late 2021.Research has shown that the Delta variant has an estimated R of 5.08 compared to the original strain's estimated R of 2.79. Hence, it's unclear if the Delta variant directly causes more severe sickness, but the fact that it is more contagious than previous variants is confirmed. Studies suggest that those who have been fully vaccinated against COVID-19 infection should be at reduced risk of becoming infected with the Delta variant.
Other variants
Other previously prevalent variants.
The diagram below shows how the Pango lineages are related to each other. For a full list of the current Pango lineages see cov-lineages.org.