The earliest known version of Omicron is B.1.1.529, before BA.1 spread to 171 countries and now BA.2 and BA.3 have been registered as new sub-variants in the Omicron family.
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There are now four strains of Omicron, the World Health Organization has warned.
The variant has developed multiple lineages since it burst onto the scene late last year.
However, this is not uncommon, as the Delta variant has evolved into more than 200 sub-variants.
Most of the strains are very similar to the original, so there are no further concerns about severity or immunity.
Health officials have repeatedly said that Covid booster shots are the most reliable way to protect against the Omicron variant.
The earliest known version of Omicron is B.1.1.529, and the WHO has named it a variant of concern.
It then developed into two strains and BA.1 became highly transmissible and spread to 171 countries.
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Many countries brought back restrictions to try to curb the rise in cases.
BA.2 and BA.3 have been registered as new subvariants in the Omicron family.
Case rates for BA.3 remain low, and for BA.2 they have been found in 426 cases of BA.2 found in England since December 6, with London leading the table with 146.
It is not known where BA.2 first originated. So far, 40 countries have uploaded more than 8,000 BA.2 sequences since mid-November.
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The first sequences were sent from the Philippines and the largest number of samples were uploaded from Denmark, where 6,411 cases were found as of Friday.
Other countries that have uploaded more than 100 samples are India (530), Sweden (181) and Singapore (127).
At this time, there is no indication that the BA.2 subvariant is more severe than the original Omicron strain.
In Denmark, this strain consisted of about half of all Omicorn cases. Initial studies from the country suggest there is no increased risk of hospitalization.
Current vaccines are also believed to be effective against the BA.2 strain in combating serious illness, according to Danish health officials.
The UK Health Security Agency (UKHSA) says the appearance of new mutations is not unexpected.
A January 21 WHO report said: “While the BA.1 lineage has previously been the most dominant, recent trends from India, South Africa, the UK and Denmark suggest that BA.2 is increasing in proportion.
“The transmission drivers and other properties of BA.2 are under investigation, but to date remain unclear.”
The most recent UKHSA data found that it appears to be able to spread faster than the original Omicron, but more research is needed to be sure as it is now officially an investigational variant.
Dr Meera Chand, UKHSA COVID-19 Incident Manager, said: “The nature of viruses is to evolve and mutate, so it is to be expected that we will continue to see new variants emerge as the pandemic progresses.
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“Our ongoing genomic surveillance allows us to detect them and assess whether they are significant.
“So far, there is insufficient evidence to determine whether BA.2 causes more severe disease than Omicron BA.1, but data is limited and UKHSA is continuing to investigate.
“Case rates remain high across the UK and we need to remain vigilant and get vaccinated. We should all continue to get tested regularly with LFD and get a PCR test if symptoms develop.”
In a statement, UKHSA said: “As is customary for any new variant under investigation, UKHSA is carrying out laboratory and epidemiological investigations to better understand the characteristics of this variant.
“We will continue to monitor this situation closely and recommend appropriate public health measures if necessary.
“Further details will be available at UKHSA’s regular variant technical briefings.”
Last week, Health and Social Care Secretary Sajid Javid said: “These data are further proof that vaccines remain our best line of defense against COVID-19.
“Booster shots are protecting people against serious infections and illnesses, so I urge you to play your part in our national mission and get a boost now.”
George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.