JN.1 Covid variant now accounts for nearly half of US cases

Here's what you need to know about the coronavirus variant, which was first detected in the United States in September.

As the holiday season draws to a close and Covid-19 cases begin to rise, a variant called JN.1 has now become the most common strain common of the virus which is spreading across the world. United States.

JN.1, which emerged from the BA.2.86 variant and was first detected in the United States in September, accounted for 44%. of Covid cases nationwide by mid-December, compared to about 7 percent in late November, according to data from the Centers for Disease Control and Prevention.

To some extent, this jump was predictable. “Variants take a while to show up,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center. "Then they accelerate, they spread widely, and just when they do that, after several months, a new variant appears."

The momentum of JN.1 this month suggests it may be more transmissible or better evade our immune systems than other variants currently circulating, according to a C.D.C. report published on December 22. The agency said Covid remains "a serious threat to public health", particularly for those who have historically been at high risk of severe illness, such as the elderly, infants, people with compromised immune systems. weakened or chronic health problems. and those who are pregnant.

As far as experts can tell, JN.1 does not appear to cause serious illness in most other people, although even a mild case can still make you feel “pretty bad”. miserable for three or four days,” Dr. Schaffner said. Symptoms of a JN.1 infection are similar to those caused by previous Covid variants, including a cough, fever, body aches and fatigue.

To protect yourself from serious infections and illnesses, experts continue to recommend wearing masks, improving indoor ventilation when possible, to stay home if sick and get vaccinated against Covid.

To protect yourself against infections and serious illnesses, experts continue to recommend wear masks, improve ventilation indoors when possible, stay home when sick, and get vaccinated against Covid. p>

Preliminary research shows that the updated Covid vaccines released in September produce effective antibodies against JN.1, which is distantly related to the XBB.1.5 variant that the vaccines have been designed to target. People may not develop as many antibodies against JN.1 as they do against XBB.1.5, but the levels should still reduce the risk.

“For those who have been recently infected or boosted, cross-protection against JN.1 should be decent, based on our laboratory studies,” said the Dr. David Ho, a virologist at Columbia University who led research on the JN.1 and Covid vaccines, which was published as a preprint paper in early December. Rapid testing also remains a valuable tool, and the C.D.C. said tests already on the market work well to detect JN.1.

There are signs that Covid cases are increasing again. There were just under 26,000 hospitalizations due to Covid the week of December 10, an increase of 10% from the 23,000 hospitalizations the week before. But Covid hospitalizations are still much lower than they were during the peak of the first Omicron wave in January 2022, and so far only about half of what they were during the peak of the tripledemic l last winter, when Covid-19, the flu and R.S.V. cases all increased at the same time.

It is too early to know if JN.1 is responsible for the increase in hospitalizations or if cases are picking up in part because of increased travel and large gatherings for Thanksgiving and winter holidays.

“When people are gathered indoors next to each other, after...