A new COVID variant known as the "XEC variant" is raising questions and capturing the attention of researchers heading into the fall and winter season.

The variant has been largely spreading overseas with countries like Denmark, Germany, the UK and the Netherlands seeing the largest spikes, but the variant has also appeared to begin a climb in the U.S., according to researchers.

So what should you know about it?

Here's an explainer:

What is the XEC variant?

According to Eric Topol, director of the Scripps Research Translational Institute in California, the XEC variant "appears to be the most likely one to get legs next."

At this juncture, the XEC variant appears to be the most likely one to get legs next. Its current status nicely tracked by @Mike_Honey_ 's threadhttps://t.co/4AnLa3MXfz

— Eric Topol (@EricTopol) September 15, 2024

Topol reported the subvariant is a "recombinant of KS.1.1 and KP.3.3" variants and has been "showing up in many countries with a growth advantage." He added, however, that it could take time to learn the variant's full extent.

The variant's rise comes from a recent mutation, Topol told the LA Times.

While KP.3, nicknamed the FLuQE variant, and its subvariant KP.3.1.1, or the deFLuQE variant, each had mutations of their own, XEC took the mutation even further, making it a "very pathogenic, very immune evasive variant."

He noted that it could be behind a recent wave that is sickening people who otherwise may not have contracted COVID.

Where is it spreading?

The variant's prominence remains largely abroad, with XEC still not widely detected enough to make it on the U.S. Centers for Disease Control and Prevention variant proportions data tracker.

According to the CDC estimates, the dominant variant in the U.S. is still KP.3.1.1, which represents more than half of COVID cases currently.

Data reported over the weekend showed the highest percentages of the variant seen in Denmark, the Netherlands, Germany and the UK.

Will vaccines prevent against the XEC variant?

Experts have long said the COVID virus will continue to mutate.

This fall's vaccine recipe is tailored to a newer branch of omicron descendants. The Pfizer and Moderna shots target a subtype called KP.2 that was common earlier this year.

While additional offshoots, particularly KP.3.1.1, now are spreading, they’re closely enough related that the vaccines promise cross-protection. It is expected that the vaccines will provide some protection against XEC as well.

A Pfizer spokesman said the company submitted data to FDA showing its updated vaccine “generates a substantially improved response” against multiple virus subtypes compared to last fall’s vaccine.

This summer’s wave of COVID-19 isn’t over but winter surges tend to be worse. And while COVID-19 vaccines do a good job preventing severe disease, hospitalization and death, protection against mild infection lasts only a few months.

What are the symptoms?

It's not clear if the new variant will bring with it a change in symptoms.

As of now, the symptoms for COVID remain the same:

• Cough
• Sore throat
• Runny nose
• Sneezing
• Fatigue
• Headache
• Muscle aches
• Altered sense of smell
• Congestion
• Fever or chills
• Shortness of breath or difficulty breathing
• Nausea or vomiting
• Diarrhea

Recent reports have centered on specific gastrointestinal symptoms related to the virus.

Dr. Katelyn Jetelina, a scientific consultant for the CDC and epidemiologist, said "gastrointestinal issues including nausea, vomiting, and diarrhea" have been previously identified as possible symptoms of COVID-19.

"We do not have specific data about the incidence of GI symptoms with the current strains of the virus, but COVID-19 symptoms can certainly differ based on the variant and the individual," Jetelina told NBC Chicago in July.

Last fall, a Chicago-area doctor said she's noticed shifts in the most common symptoms her patients reported as the JN.1 variant rose to dominance.

Dr. Chantel Tinfang, a family medicine physician with Sengstacke Health Center at Provident Hospital of Cook County, noted at the time that many of the cases she saw reported less of the fever, body aches and chills, and presented more with sore throat, fatigue and coughing.

"We still see some patients experiencing decreased appetite, a loss of taste or smell. So it kind of depends," she said. "One patient was just very, very tired. Like she couldn't really do much. And that's when you know ... it's different. It's not just coughing and shortness of breath. We still see that though."

She suggested consulting with your doctor if your symptoms don't begin to improve outside of the recommended isolation period.

How long does COVID last?

As for timing, symptoms can last for several days, but in some cases, even longer.

"Some people who have been infected with the virus that causes COVID-19 can experience long-term effects from their infection, known as Long COVID or Post-COVID Conditions (PCC)," according to the CDC.

Such symptoms can last for weeks and possibly even years.

Previous timing guidelines centered around five to 10 days, however.

What to do if you test positive?

In March, the CDC updated its COVID guidelines to mirror guidance for other respiratory infections. Those who contracted COVID-19 no longer need to stay away from others for five days, the CDC said, effectively nixing the five-day isolation recommendation.

People can return to work or regular activities if their symptoms are mild and improving and it's been a day since they've had a fever, but the CDC still recommends those with symptoms stay home.

"The recommendations suggest returning to normal activities when, for at least 24 hours, symptoms are improving overall, and if a fever was present, it has been gone without use of a fever-reducing medication," the guidance states.

Once activities are resumed, the CDC still recommends "additional prevention strategies" for an additional five days, including wearing a mask and keeping distance from others.

The agency is emphasizing that people should still try to prevent infections in the first place, by getting vaccinated, washing their hands, and taking steps to bring in more outdoor fresh air.

As part of the guidance, the CDC suggests:

• Staying up to date with vaccination to protect people against serious illness, hospitalization, and death. This includes flu, COVID-19, and RSV if eligible.
• Practicing good hygiene by covering coughs and sneezes, washing or sanitizing hands often, and cleaning frequently touched surfaces.
• Taking steps for cleaner air, such as bringing in more fresh outside air, purifying indoor air, or gathering outdoors. 

The change comes at a time when COVID-19 is no longer the public health menace it once was. It dropped from being the nation's third leading cause of death early in the pandemic to 10th last year.

Most people have some degree of immunity to the coronavirus from past vaccinations or from infections. And many people are not following the five-day isolation guidance anyway, some experts say.

Where can you get free COVID tests?

On the heels of the summer wave of COVID-19 cases, Americans will be able to get free virus test kits mailed to their homes, starting in late September.

U.S. households will be able to order up to four COVID-19 nasal swab tests when the federal program reopens, according to the website, COVIDtests.gov. The U.S. Health and Human Services agency that oversees the testing has not announced an exact date for ordering to begin.

The tests will detect current virus strains and can be ordered ahead of the holiday season when family and friends gather for celebrations, an HHS spokesperson said in an emailed statement. Over-the-counter COVID-19 at-home tests typically cost around $11, as of last year.