Conn. (WTNH) — A new omicron subvariant is spreading fast, leading to an uptick in positive cases across the country.

After being first detected in Connecticut and New York in late October, XBB.1.5 is now the dominant COVID strain in the United States and makes up 75% of new cases in the northeast, according to the CDC. 

“Pandora’s box has been opened. I don’t think we can pack that all back in,” Chief Epidemiologist at Hartford HealthCare, Dr. Ulysses Wu said.

What we know about XBB.1.5, the dominant COVID variant in the US

Although not considered a “super variant,” it does come with immune evasion. Wu said holiday festivities and travel fueled a rise in cases and hospitalizations, and many are getting sick more than once.

“This variant has [the] ability to bind to your cells, so transmission is much more efficient… People who have had COVID before, it may not your immune system recognize this new variant, so you may get infected again,” Wu said.

Wu expects cases to peak with the new variant in the coming weeks to reduce transmission. He said people should stay away from others if they are sick and mask up in indoor and social settings.

Health officials recommend people receive their COVID vaccines and boosters to help prevent severe illness.

“The goal here is to reduce transmission, which will limit the rate, the rise, and the increase [of] these new mutations,” Wu said.

While 68% of Americans received both doses of the COVID vaccine, only about a third have received a booster dose.

“We don’t want people laid out in the hospital when they can be productive members of society. We don’t want people dying; that’s what it comes down to, reducing it to a common cold,” Wu said.