Experts explain what's making BA.2 omicron subvariant more contagious than the original

SAN FRANCISCO (KGO) -- There's a new "subvariant" of the omicron variant that's been spreading across Europe and the U.S.

Preliminary data shows it's more contagious than omicron. Scientist have named it BA.2 a variant that's closely related to the original omicron strain.

"In Denmark where it's sort of taken over it looks like it's 1 and a half times more infectious than the original omicron which was more infectious than delta," said Dr. Deepak Srivastava, President of the Gladstone Institutes.

The CDC confirmed BA.2 is circulating at a low level in the US. Two cases of BA.2 were confirmed in Santa Clara County last week. Is it worse than omicron or delta? Dr. Srivastava explains.

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"It looks like this is going to transmit more, but so far it looks like it's not more severe, but we still need to study that," said Dr. Srivastava.

UCSF Professor Nevan Krogan is the Director of Quantitative Biosciences Institute. He broke down BA.2 in comparison to the original omicron strain.

"In many ways they are similar. Each have about 50 mutations. There are 30 mutations that are overlapping between these two viruses," said Professor Krogan.

Professor Krogan's team identify the section where the majority of transmission is forming within the BA.2 variant.

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"There's a couple other ones here that we think may be involved in suppressing the immune response. This new variant may be more effective in doing that versus the original variant," said Professor Krogran.

Experts are also calling BA.2 "stealth omicron." They've noticed there's a key difference in its genetic sequence that makes it harder to track.

"It does not have a mutation in a region that makes it drop out so it looks very much like delta on a PCR test so you can't tell the difference, and that is why we call it stealth," said Dr. Srivastava.

Both experts agree vaccines and boosters continue to be effective against both strains.

"I don't think we should be concerned every time. We should realize that the virus mutates. I think there should be some satisfaction knowing that the scientific world has tools that we've never had before," said Professor Krogan.