In about a month it will be the first anniversary of when the omicron variant of COVID-19 shook governments and public health services around the world. Since then, omicron has had many subvariants, some of which have become dominant strains across the globe.

While omicron BA.5 is still dominant in much of the world, two new subvariants (BQ.1 and BQ.1.1) are now accounting for over 11% of all cases in the United States—and experts believe they could cause havoc this winter. Here’s what you need to know:

What are BQ.1 and BQ.1.1? They are new subvariants of the omicron strain of COVID-19. Health experts worry their qualities could lead to a resurgence in COVID-19 cases as America enters the colder winter months and sees an increase in holiday gatherings.

Are BQ.1 and BQ.1.1 more transmissible and do they cause more serious disease? As CNBC reports, Dr. Anthoney Fauci says the “doubling time” of BQ.1 and BQ.1.1 is concerning. They can spread more quickly than the BA.5 variant. Further, a Chinese study, which has not been peer-reviewed yet, found that BQ.1.1’s ability to evade antibodies far exceeded BA.5 and that it was also capable of evading the immunity a person got from a previous BA.5 infection. BQ.1.1 may also be able to evade some antibody therapies, meaning it could be more deadly than BA.5 for certain groups of people. At this early stage, it’s important to point out that there are still a lot of unknowns here.

How widespread are BQ.1 and BQ.1.1 in America? According to data published by the Centers for Disease Control and Prevention (CDC), BQ.1 and BQ.1.1 now make up about 5.7% of cases each, so 11.4% of cases in total as of October 15.

Some areas of the country have higher rates of BQ.1 and BQ.1.1 than others. Here’s what the CDC’s NowCast tracker shows regarding the spread of BQ.1 and BQ.1.1 across the country:

New York/New Jersey area: BQ.1 makes up 11.6% of cases. BQ.1.1 makes up 8% of cases.

Upper Northeast: Includes states such as Massachusetts and Maine. BQ.1 makes up 3.1% of cases. BQ.1.1 makes up 4.0% of cases.

West Coast: Includes California, Washington, and Oregon. BQ.1 makes up 3.8% of cases in California and 0.8% of cases in Washington and Oregon. BQ.1.1 makes up 5.2% of cases in California and 4.5% of cases in Washington and Oregon.

South East: Includes states such as North and South Carolina. BQ.1 makes up 3.8% of cases. BQ.1.1 makes up 7.5% of cases.

South Central: Includes states such as Texas and New Mexico. BQ.1 makes up 11.5% of cases. BQ.1.1 makes up 1.2% of cases.

South: Includes states such as Florida and Alabama. BQ.1 makes up 4.9% of cases. BQ.1.1 makes up 3.1% of cases.

You can check out the CDC’s latest Nowcast map here.