“It might be, from a human’s perspective, a worse virus than BA.1 and might be able to transmit better and cause worse disease,” says Dr. Daniel Rhoads, section head of microbiology at the Cleveland Clinic in Ohio. Rhoads reviewed the study but was not involved in the research.
The US Centers for Disease Control and Prevention is keeping a close eye on BA.2, said its director, Dr. Rochelle Walensky.
“There is no evidence that the BA.2 lineage is more severe than the BA.1 lineage. CDC continues to monitor variants that are circulating both domestically and internationally,” she said Friday. “We will continue to monitor emerging data on disease severity in humans and findings from papers like this conducted in laboratory settings.”
BA.2 is highly mutated compared with the original Covid-causing virus that emerged in Wuhan, China. It also has dozens of gene changes that are different from the original Omicron strain, making it as distinct from the most recent pandemic virus as the Alpha, Beta, Gamma and Delta variants were from each other.
Kei Sato, a researcher at the University of Tokyo who conducted the study, argues that these findings prove that BA.2 should not be considered a type of Omicron and that it needs to be more closely monitored. “As you may know, BA.2 is called ‘stealth Omicron,’ ” Sato told CNN. That’s because it doesn’t show up on PCR tests as an S-gene target failure, the way Omicron does. Labs therefore have to take an extra step and sequence the virus to find this variant. “Establishing a method to detect BA.2 specifically would be the first thing” many countries need to do, he says. “It looks like we might be looking at a new Greek letter here,” agreed Deborah Fuller, a virologist at the University of Washington School of Medicine, who reviewed the study but was not part of the research.
Mixed real-world data on subvariant’s severity
BA.2 has been estimated to be about 30% more contagious than Omicron, according to the World Health Organization. It has been detected in 74 countries and 47 US states.
The US Centers for Disease Control and Prevention estimates that about 4% of Americans with Covid-19 now have infections caused by BA.2, but many other parts of the world have more experience with this variant. It has become dominant in at least 10 other countries: Bangladesh, Brunei, China, Denmark, Guam, India, Montenegro, Nepal, Pakistan and the Philippines, according to World Health Organization’s weekly epidemiological report. However, there’s mixed evidence on the severity of BA.2 in the real world. Hospitalizations continue to decline in countries where BA.2 has gained a foothold, like South Africa and the UK.
But in Denmark, where BA.2 has become the leading cause of infections, hospitalizations and deaths are rising, according to WHO.