The Omicron subvariants BQ.1 and BQ.1.1 were projected to account for around 44.2% of COVID-19 cases in the nation for the week ending Nov. 12, according to the U.S. national public health agency, up from 32.6% the week before.

The two variants made up less than 10% of all cases in the nation last month, but they currently outnumber Omicron’s BA.5, according to the U.S. Centers for Disease Control and Prevention. They are closely related to Omicron’s BA.5 sub-variant, which was the cause of COVID-19 cases in the United States earlier this year.

BQ.1.1 accounted for nearly 24.1% of circulating variants and BQ.1 was estimated to make up 20.1% of circulating cases for the week ending Nov. 12, the U.S. CDC said.

While there is no evidence linked to the increased severity of the new variants compared to BA.4 and BA.5, they have shown an increasing presence in Europe, Singapore, Canada, among other places.

The rising trend has lead regulators and vaccine manufacturers to monitor the new variants more closely in case they start to evade protection offered by current vaccines.

The BA.5 subvariant is estimated to make up about 29.7% of cases in the United Sates, compared with nearly 41.1% in the week ended Nov. 5, according to the CDC.