A new, fast-spreading COVID variant is sweeping across the nation, making it the most widely circulating iteration of the virus in the U.S. and around the world, according to the Centers for Disease Control and Prevention.

The mutation, called JN.1, is a subvariant of Omicron that was first detected by the World Health Organization in late August. At the time it appeared to be spreading slowly but as temperatures have dipped, JN.1 has spiked.

In mid-October, CDC data showed JN.1 made up about 0.1% of all COVID cases around the country. As of Jan. 20, the CDC estimates that’s now up to approximately 86%.

“Most likely, if you’re getting COVID right now, you’re getting this particular variant mutation,” said Eyal Oren, a director and professor of epidemiology at the School of Public Health at San Diego State University.

Oren added that one of the reasons for the latest surge is that the virus continues to evolve so rapidly that “our immune systems have not been able to keep up.”

Another reason is that “not enough Americans are vaccinated,” according to the CDC. Earlier this month, only 11% of children and 21% of adults were reported to have received the updated COVID vaccine. Meanwhile, only 40% of adults age 65 and older, which is the highest risk group, have gotten the updated vaccine in the last year.

The CDC says COVID vaccines can reduce severe illness and hospitalizations.

The low rates for vaccinations, along with those against influenza and respiratory syncytial virus (RSV), are of such great concern that the CDC issued an alert to healthcare workers last month. The combination of rising flu, RSV and COVID cases “could lead to more severe disease and increased healthcare capacity strain in the coming weeks,” the agency predicted.

People may be wrongly assuming that the current COVID booster won’t protect them from JN.1 or other new strains, Oren said. But the most recent vaccines from Pfizer-BioNTech, Moderna and Novavax are all expected to help lower chances of serious illness or hospitalization from JN.1.

What are the symptoms of JN.1?

CDC data indicates that this strain is no more severe than previous iterations, and the list of symptoms remains consistent with what they have been for COVID in recent years: fever, chills, coughing, muscle aches, shortness of breath, sore throat, congestion, headaches, fatigue, and losing one’s taste or smell.

Oren noted that most of the list consists of ailments that could be confused with those caused by other viruses common during winter months, including the flu, RSV or the common cold.

“That’s why it’s so important to get vaccinated and to get tested [for COVID], particularly if someone is at higher risk of severe outcomes,” he said.

How to stay safe

Oren urged all people, but especially those in high-risk categories, to take precautions by wearing masks, avoiding crowded places, and washing their hands. “And if you’re sick stay home,” he said.

The CDC reported that over the last 4 weeks, hospitalizations among all age groups increased, by 200% for influenza, 51% for COVID-19, and 60% for RSV.

The federal government offers free rapid COVID-19 tests through the mail. Four free tests can be ordered at COVIDTests.gov and will be delivered by the U.S. Postal Service.