As holiday travel peaks in the United States, a heavily mutated new COVID-19 variant called JN.1 is spreading rapidly and fueling an increasing number of infections.
The highly contagious omicron subvariant is now the dominant strain nationwide and accounts for nearly half of all cases.
JN.1 is currently the fastest-growing variant in the country, according to the U.S. Centers for Disease Control and Prevention.
During a two-week period ending on Dec. 23, JN.1 made up an estimated 44% of cases in the U.S., per the CDC’s latest data. After JN.1, the next most common strain was the HV.1 subvariant, which accounted for about 22% of cases nationwide. At the end of November, JN.1 only made up about 8% of cases.
Respiratory virus season has yet to peak in the U.S., which means COVID-19 cases are expected to rise in the coming weeks.
JN.1 is also gaining speed in many other countries. Earlier this week, the World Health Organization classified JN.1 as a “variant of interest” due to its “rapidly increasing spread” globally.
Scientists around the world are closely monitoring JN.1, which has sparked some concern due to its rapid growth rate and large number of mutations. However, the new variant is closely related to a strain we’ve seen before. It’s a direct offshoot of BA.2.86, aka “Pirola,” which has been spreading in the U.S. since the summer.
JN.1 has one extra mutation compared to BA.2.86, which has more than 30 mutations that set it apart from the omicron XBB.1.5 variant. XBB.1.5 was the dominant strain for most of 2023 and it’s the variant targeted in the updated COVID-19 vaccines, TODAY.com previously reported.
All of the most prevalent COVID-19 variants in the U.S. right now are descendants of omicron, which began circulating in late 2021.
During the last few weeks, JN.1 quickly overtook many other variants, including its parental strain BA.2.86, as well as HV.1, EG.5 or Eris and XBB.1.16 aka Arcturus.
JN.1’s growth comes as COVID hospitalizations rise, influenza continues to spread and RSV activity is high in many places, according to a Dec. 14 update from the CDC. The agency warned that at the end of the month, emergency rooms and hospitals could become strained, similarly to last year, especially in the South.
Will JN.1 cause a COVID-19 surge? Does JN.1 have different symptoms and is it detected by COVID tests? Does it respond to vaccines and treatments? Here’s what experts know about JN.1 so far.
JN.1 was first reported in August 2023 and it has spread to at least 41 countries so far, according to the WHO. It was first detected in the U.S. in September, the CDC said.
Just like the other newer variants, JN.1 is part of the omicron family.
“Think of (the variants) as children and grandchildren of omicron. They’re part of the same extended family, but they each have their own distinctive personalities,” Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, tells TODAY.com.
JN.1 descended from BA.2.86, which is a sublineage of the omicron BA.2 variant, TODAY.com previously reported — that’s what sets JN.1 and BA.2.86 apart from the other prevailing variants like HV.1 and EG.5, which descended from omicron XBB.
“When its parent BA.2.86 emerged, everybody was worried because it had a lot of mutations and looked like it was going to evade a lot of the immunity from vaccines and infection in the population,” Andrew Pekosz, Ph.D., professor and vice chair in the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health, tells TODAY.com. “But (BA.2.86) sort of fizzled out,” he adds.
Laboratory data suggest that Pirola is less contagious and immune-evasive than scientists once feared, NBC News reported.
JN.1, however, picked up an additional mutation in its spike protein called L455S, says Pekosz. Spike proteins help the virus latch onto human cells and play a crucial role in helping SARS-CoV-2 infect people, per the CDC. This mutation may affect JN.1’s immune escape properties, says Pekosz.
“Now it’s circulating and growing at a really fast rate compared to other variants, as well as the parent it’s derived from (BA.2.86),” says Pekosz.
In early November, JN.1 accounted for fewer than 1% of COVID-19 cases in the U.S. Several weeks later, it was driving over 20% of cases, Dr. Michael Phillips, chief epidemiologist at NYU Langone Health, tells TODAY.com. Now, it’s the dominant strain in the U.S.
