Amid the ongoing flu season, health officials have identified a new strain of the influenza virus, as confirmed by the Centers for Disease Control and Prevention (CDC).

This emerging variant is a subset of influenza A, specifically a K subclade of the H3N2 subtype. Currently, it accounts for the majority of reported H3N2 cases.

Historically, the H3N2 strain has been linked to higher hospitalization and mortality rates among the elderly compared to other influenza strains. Experts caution that this winter could usher in a particularly severe flu season, especially if vaccination uptake remains low.

“I anticipate a very intense season,” said Asefeh Faraz Covelli, an associate professor at the George Washington University School of Nursing, in a statement to the Associated Press.

What are the symptoms of the new K variant?

The K subclade doesn’t appear to cause markedly different symptoms than other types of flu; however, as a subtype of influenza A, its symptoms may be more serious.

“Influenza A typically causes worse symptoms compared to influenza B, and patients are more likely to get hospitalized with influenza A compared to influenza B,” Dr. Donald Dumford, an infectious disease specialist at Cleveland Clinic, told Nexstar.

Flu symptoms can be mild or severe, but they usually come on quickly, according to the CDC. Signs include fever, cough, sore throat, congestion, body aches, headaches and fatigue. Not everyone with the flu will experience all the possible symptoms.

People who have trouble breathing, severe pain, weakness, or aren’t seeing symptoms improve should seek urgent medical care, the CDC advises. Younger children and older adults, who are more vulnerable to flu complications, may need care sooner.

Are this year’s flu shots effective against it?

A preliminary analysis from the United Kingdom suggests the shots do provide at least partial protection, although it will take some time for scientists to know exactly how effective they are.

Experts say any protection that softens the blow of a flu infection is important to get. Even vaccines that aren’t perfectly formulated to match a new variant can often still give “cross-protection” and boost your immune response.

Public health experts are more concerned about vaccination uptake than vaccination matching.

“The thing that really concerns me most is the decreasing rates of influenza vaccination, particularly among children,” Andrew Pavia, a professor and pediatric infectious disease expert at the University of Utah, told The Hill last week.

“We don’t claim the vaccine to be perfect, it’s not, [but] it works better at keeping you out of the hospital, the intensive care unit and helping keep you out of the cemetery,” Dr. William Schaffner, a professor at Vanderbilt University’s Department of Health Policy, added.

Where is flu spreading most?

CDC data posted in mid-November showed low flu activity so far, with only one state — Louisiana — reporting moderate activity. Most of the reported infections have been in children, said the CDC’s Alicia Budd, who tracks flu infections for the Atlanta-based agency.

Colorado and Mississippi also saw flu activity rise from “minimal” in October to “low” in November.

Some recent federal flu data is delayed by the government shutdown and Thanksgiving holiday, but from what we can tell the virus isn’t circulating at abnormally high levels nationwide just yet. That could soon change, as flu seasons tend to get bad between December and February.

“I think it’s going to start picking up here,” Covelli said.

The Associated Press contributed to this report.