For most of this year, the JN.1 variant of the coronavirus accounted for an overwhelming majority of Covid cases. But now, an offshoot variant called KP.2 is taking off. The variant, which made up just one percent of cases in the United States in mid-March, now makes up over a quarter.
KP.2 belongs to a subset of Covid variants that scientists have cheekily nicknamed “FLiRT,” drawn from the letters in the names of their mutations. They are descendants of JN.1, and KP.2 is “very, very close” to JN.1, said Dr. David Ho, a virologist at Columbia University. But Dr. Ho has conducted early lab tests in cells that suggest that slight differences in KP.2’s spike protein might make it better at evading our immune defenses and slightly more infectious than JN.1.
While cases currently don’t appear to be on the rise, researchers and physicians are closely watching whether the variant will drive a summer surge.
“I don’t think anybody’s expecting things to change abruptly, necessarily,” said Dr. Marc Sala, co-director of the Northwestern Medicine Comprehensive Covid-19 Center in Chicago. But KP.2 will most likely “be our new norm,’” he said. Here’s what to know.
The current spread of Covid
Experts said it would take several weeks to see whether KP.2 might lead to a rise in Covid cases, and noted that we have only a limited understanding of how the virus is spreading. Since the public health emergency ended, there is less robust data available on cases, and doctors said fewer people were using Covid tests.
But what we do know is reassuring: Despite the shift in variants, data from the C.D.C. suggests there are only “minimal” levels of the virus circulating in wastewater nationally, and emergency department visits and hospitalizations fell between early March and late April.
“I don’t want to say that we already know everything about KP.2,” said Dr. Ziyad Al-Aly, the chief of research and development at the Veterans Affairs St. Louis Healthcare System. “But at this time, I’m not seeing any major indications of anything ominous.”
Protection from vaccines and past infections
Experts said that even if you had JN.1, you may still get reinfected with KP.2 — particularly if it’s been several months or longer since your last bout of Covid.
KP.2 could infect even people who got the most updated vaccine, Dr. Ho said, since that shot targets XBB.1.5, a variant that is notably different from JN.1 and its descendants. An early version of a paper released in April by researchers in Japan suggested that KP.2 might be more adept than JN.1 at infecting people who received the most recent Covid vaccine. (The research has not yet been peer-reviewed or published.) A spokesperson for the C.D.C. said the agency was continuing to monitor how vaccines perform against KP.2.
Still, the shot does provide some protection, especially against severe disease, doctors said, as do previous infections. At this point, there isn’t reason to believe that KP.2 would cause more severe illness than other strains, the C.D.C. spokesperson said. But people who are 65 and older, pregnant or immunocompromised remain at higher risk of serious complications from Covid.
Those groups, in particular, may want to get the updated vaccine if they haven’t yet, said Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco. The C.D.C. has recommended that people 65 and older who already received one dose of the updated vaccine get an additional shot at least four months later.
“Even though it’s the lowest level of deaths and hospitalizations we’ve seen, I’m still taking care of sick people with Covid,” he said. “And they all have one unifying theme, which is that they’re older and they didn’t get the latest shot.”
The latest on symptoms and long Covid
Doctors said that the symptoms of both KP.2 and JN.1 — which now makes up around 16 percent of cases — are most likely similar to those seen with other variants. These include sore throat, runny nose, coughing, head and body aches, fever, congestion, fatigue and in severe cases, shortness of breath. Fewer people lose their sense of taste and smell now than did at the start of the pandemic, but some people will still experience those symptoms.
Dr. Chin-Hong said that patients were often surprised that diarrhea, nausea and vomiting could be Covid symptoms as well, and that they sometimes confused those issues as signs that they had norovirus.
For many people who’ve already had Covid, a reinfection is often as mild or milder than their first case. While new cases of long Covid are less common now than they were at the start of the pandemic, repeat infections do raise the risk of developing long Covid, said Fikadu Tafesse, a virologist at Oregon Health & Science University. But researchers are still trying to determine by how much — one of many issues scientists are trying to untangle as the pandemic continues to evolve.
“That’s the nature of the virus,” Dr. Tafesse said. “It keeps mutating.”
