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WHO studying Omicron BA.3: How contagious is it? Can it cause ‘severe disease’

The World Health Organisation (WHO) has said it is tracking several sublineages of Covid variant Omicron, including BA.1, BA.1.1, BA.2, and BA.3. The global health body is also looking at real-world data on whether, experimentally within hamsters, these Omicron subvariants could cause “more severe disease” under these experimental conditions.

We all know about two of the most prominent sublineages of the new Covid variant Omicron i.e BA.1 and BA.2. The World Health Organisation (WHO) has now said along with these two Covid subvariants, it’s tracking another sublineage called BA.3 by looking at real-world data to assess it causes “more severe disease”.

WHO’s top infectious disease expert Maria Van Kerkhove has said Omicron still remains “a variant of concern” and that the WHO is tracking Omicron in several sublineages. “The most prominent ones that are detected worldwide are BA.1, BA.1.1 and BA.2. There’s also BA.3 and other sublineages as well,” she said.

To know more about this Omicron sublineage, a study titled ‘Emergence of Omicron third lineage BA.3 and its importance’, and published in the Journal of Medical Virology, was conducted in January. It sheds light on how the global health bodies should be looking at Omicron BA.3.

Also read: ‘There’s also Omicron BA.3’: What WHO says on Covid severity signals in people

What is Omcron BA.3?

After the emergence of Omcron in November 2021 in Botswana, the WHO classified it as the fifth variant of concern. It found that Omicron was also the most mutated variant of SARS-CoV-2 so far, which had now circulated in 150 countries/territories until January 8, 2022. Omicron has three lineages BA.1, BA.2, and BA.3. The study showed that both BA.1 and BA.2 lineages differ in their spike protein but there were no specific mutations for the BA.3 lineage in spike protein, it said, adding that it’s a combination of mutations in BA.1 and BA.2 spike proteins.

When was Omicron BA.3 detected?

All three lineages were first detected at around the same time and from the same place: BA.1 (Botswana), BA.2 (South Africa) and BA.3 (North West South Africa). “Therefore, viruses that develop simultaneously and from the same place have equal chances of spreading worldwide,” the study showed.

Though all the three lineages have spread worldwide, the rate of spread of these three lineages is different. “Of these three lineages, it is questionable why only BA.1 dominates much more than the other lineages. This is likely due to differences in mutations in the spike protein required for virus transmission and host cell entry,” the study showed.

Also read: Should we worry about Omicron BA.2? WHO explains Japanese lab study

How contagious is BA.3?

The study found that of the 33 mutations in the BA.3 lineage spike protein, 31 mutations are common to BA.1. “BA.3 lineage caused the lowest number of cases in these three lineages. Therefore, it can be speculated that the reason for the BA.3 lineage spreading at very low speeds and causing fewer cases may have been due to the loss of six mutations from BA.1 or obtaining two mutations from BA.2,” the study found.

The study said Omicron has so far been thought to cause mild disease, but “it is also possible to develop some mutations” that can lead to serious illness.

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