CDC Reveals New ‘Fastest-Growing’ COVID-19 Variant in US

The CDC said it’s unclear to what extent JN.1 is contributing to hospitalizations

The Centers for Disease Control and Prevention (CDC) headquarters in Atlanta on April 23, 2020. Tami Chappell/AFP via Getty Images

The U.S. Centers for Disease Control and Prevention (CDC) indicated that the JN.1 COVID-19 subvariant is increasingly across the United States, comprising potentially a third of all cases.

The variant comprised about 0.1 percent of all COVID-19 cases in the United States as of late October, according to the federal health agency in a Dec. 8 update. But as of Dec. 8, it now makes up about 15 to 29 percent of cases, it said.

“CDC projects that JN.1 will continue to increase as a proportion of SARS-CoV-2 genomic sequences,” the CDC said. “It is currently the fastest-growing variant in the United States.”

The CDC said in another update that the JN.1 level jumped from 8.1 percent to 21.4 percent in the past two weeks. JN.1 is now the second-most common variant in the U.S., behind only the HV.1 variant, according to the CDC.

Despite the fast growth of JN.1, there is “no evidence” at this time that it “presents an increased risk to public health relative to other currently circulating variants,” said the CDC. There is also no signs of “increased severity” from the variant, the agency added.

Current COVID-19 treatments and tests are believed to be effective against JN.1, it said, adding that “the continued growth of JN.1 suggests that it is either more transmissible or better at evading our immune systems.”

The CDC also said it’s unclear to what extent JN.1 is contributing to hospitalizations in the U.S. but said that COVID-19 activity is likely going to increase during the winter months.

Researchers and the CDC say that JN.1 is a COVID-19 variant that descended from the BA.2.86 lineage, which is another Omicron sub-variant.

“BA.2.86 has more than 20 mutations on the spike protein and there was a concern when it was first detected a while back that, wow, this might be a real problem,” Thomas Russo,  professor and chief of infectious diseases at the University at Buffalo in New York, told Prevention.

Symptoms

There is no data to indicate if JN.1 causes any new symptoms, said William Schaffner, a professor at the Vanderbilt University School of Medicine.

“It’s an Omicron variant and looks to be similar,” he told the outlet.

The CDC says that symptoms include cough, shortness of breath, fever or chills, fatigue, muscle aches, loss of taste or smell, sore throat, runny nose, headache, vomiting, diarrhea, or nausea.

“It is not currently known whether JN.1 infection produces different symptoms from other variants,” said the CDC update. “In general, symptoms of COVID-19 tend to be similar across variants. The types of symptoms and how severe they are usually depend more on a person’s immunity and overall health rather than which variant causes the infection.”

Other Respiratory Illnesses

At least 15 states are seeing “very high” or “high” levels of respiratory illness cases, the CDC said in a recent update.

A map posted by the CDC on Dec. 8 shows that 15 states as well as New York City are seeing “high” or “very high” levels of influenza, RSV, COVID-19, or the common cold.

RSV, or respiratory syncytial virus, is a common cause of mild cold-like symptoms, but it can be dangerous for small children and older adults, health officials have said.

“The amount of respiratory illness (fever plus cough or sore throat) causing people to seek healthcare is elevated or increasing across most areas of the country. CDC is actively following up with health departments in these communities,” the agency said. “Emergency department visits due to influenza and COVID-19 are increasing, while visits due to RSV decreased slightly nationally.”

Separate data provided by the CDC show that while COVID-19 hospitalizations have been on the rise in recent weeks, weekly COVID-19 hospitalizations have not reached the same levels as previous “surges” earlier on in the pandemic. As of the week ending Dec. 2, there were 22,513 recorded hospitalizations, which is significantly lower than the same weekly period in December 2022.

Parents with children suffering from respiratory illnesses line up at a children's hospital in Chongqing, China, on Nov. 23, 2023. CFOTO/Future Publishing via Getty Images

Flu hospitalizations are on the rise although the number of new admissions appears to be low with 5,753 admitted to the week ending on Dec. 2, which is an increase from 4,268 during the prior week, according to the most recent CDC data. The also data suggests that there have been 2.6 million influenza cases, 26,000 hospital cases, and 1,600 deaths during the flu season so far.

Earlier this month, the CDC said that despite reported spikes of pneumonia cases among children in several states, the CDC’s director, Mandy Cohen, said earlier this month that transmission rates are considered “typical.”

“As of today, we are not seeing anything that is atypical in terms of pneumonia-related emergency department visits,” she told reporters.

It came amid concerns that a spate of pediatric pneumonia cases in mainland China could spread to the U.S., which drew an alert from the ProMed global surveillance system in late November.