U.S. health regulators on Friday estimated that BQ.1 and closely related BQ.1.1 accounted for 16.6% of coronavirus variants in the country, nearly doubling from last week, while Europe expects them to become the dominant variants in a month.
The European Centre for Disease Prevention and Control said the variants are likely to drive up cases in the coming weeks to months in the European region.
The two variants are descendants of Omicron's BA.5 subvariant, which is the dominant form of the coronavirus in the United States. Regulators in Europe and the United States have recently authorized vaccine boosters that target it.
There is no evidence yet that BQ.1 is linked with increased severity compared to the circulating Omicron variants BA.4 and BA.5, European officials said, but warned it may evade some immune protection, citing laboratory studies in Asia.
In the United States, weekly cases have been falling recently, according to data from the U.S. Centers for Disease Control and Prevention (CDC).
The amount of coronavirus found in wastewater samples tested by Biobot Analytics has been basically flat around the United States over the last six weeks. Wastewater samples often predict possible spikes in COVID-19 ahead of the CDC data.
New variants are monitored closely by regulators and vaccine manufacturers in case they start to evade protection offered by current shots.
The World Health Organization this week said BQ.1.1 is circulating in at least 29 countries.
"The more this virus circulates, the more opportunities it has to change," the UN agency's technical lead on COVID Maria Van Kerkhove told reporters.
The U.S. CDC said on Friday BQ.1 last week was estimated to make up 5.8% of circulating variants, while BQ.1.1 had accounted for 3.6% of all variants.