In the rapidly changing world of COVID-19 strains, JN.1 is the latest variant fueling public health concerns. A descendant of omicron, JN.1 has risen to account for more than 1 in 5 COVID cases as of December 9 — a sharp rise from the end of October when it made up less than 0.1 percent of coronavirus infections.
The Centers for Disease Control and Prevention (CDC) is now calling JN.1 the fastest-growing variant in the United States.
“The continued growth of JN.1 suggests that it is either more transmissible or better at evading our immune systems,” wrote the CDC in an update last week.
The federal health agency emphasized, however, that there is no evidence that JN.1 causes more severe illness or poses increased risk to public health relative to other currently circulating variants, such as HV.1, which accounts for nearly 30 percent of current COVID-19 cases.
Also, COVID-19 tests and treatments are expected to be effective against JN.1, according to the CDC.
COVID-19 Indicators Climb in the U.S.
The jump in JN.1 infections corresponds with a rise in all major COVID-19 markers. The CDC’s latest tracking shows that COVID-related deaths have climbed by 25 percent in the most recent week. In addition, hospitalizations are up by more than 17 percent, emergency visits due to COVID-19 have increased by 4 percent, and test positivity has inched higher by 0.9 percent.
Hospitalizations were notably high in Montana, South Dakota, and West Virginia. States reporting big increases in deaths include Alabama, Maine, Maryland, Minnesota, Missouri, and West Virginia.
“COVID is starting to increase again after being stable for the past few weeks,” said the CDC’s director, Mandy Cohen, MD, MPH, in a video message last week. She further warned that we can expect respiratory illnesses in general to rise through the holidays as flu and RSV activity has also been elevated.
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With more people traveling and gathering together for the holidays, Dr. Cohen is urging the public to take precautions: Get vaccinated, wash your hands more frequently, improve ventilation, wear a mask in crowds, and stay home when sick so as not to spread illness.
Wastewater surveillance indicates that more trouble may be on the horizon. Nationally, the wastewater viral activity level for COVID-19 is currently “high.” The data suggest that viral activity may soon be increasing.
Why JN.1 Stands Out
JN.1 is related to the omicron family of variants. It’s a direct offspring of the omicron subvariant BA.2.86 (also called Pirola), which gained notice in the summer because of its high number of spike protein mutations.
JN.1 has an additional spike mutation, which enables it to infect cells more easily, according to Jesse Bloom, PhD, a professor at the Fred Hutchinson Cancer Center in Seattle, who studies virus evolution.
“There are also several other new variants in the BA.2.86 family. So it is possible, although still not certain, that they will spread to become the dominant SARS-CoV-2 variants,” says Dr. Bloom.
A study from Japan presented December 9 on BioRxiv, an online archive of complete but yet-to-be published scientific papers, confirmed that JN.1 is more contagious and evades immune systems better than previous strains.
“We’re lucky that the booster provides protection against it, but too few have taken advantage to date,” wrote Eric Topol, MD, the director of the Scripps Research Translational Institute, earlier this month. Only 17 percent of Americans have received the most recent booster, according to the CDC.
The vaccine can be especially vital in protecting those most vulnerable, including people 65 and older and those who are immune-compromised, such as those who are getting chemotherapy for cancer or people with rheumatic diseases who are taking monoclonal antibodies.