Covid Variant Jn 1 Symptoms

[Abigail Tyrie]

NoteInformation in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

The good news is that in the early spring of 2024, COVID-19 cases were down, with far fewer infections and hospitalizations than were seen in the previous winter. But SARS-CoV-2, the coronavirus that causes COVID, is still mutating, raising concerns about a potential wave of infections this summer. In April, a group of new virus strains known as the FLiRT variants (based on the technical names of their two mutations) began to spread, followed in June by a variant known as LB.1.

The FLiRT strains are subvariants of Omicron, and together they accounted for the majority of COVID cases in the U.S. at the beginning of July. One of them, KP.3, was responsible for 36.9% of COVID infections in the United States, KP.2 made up 24.4%, and KP.1.1 accounted for 9.2% of cases.

The LB.1 strain, which similar to the FLiRT variants but with an additional mutation, has attracted attention as well. As summer began, it was responsible for 14.9% of COVID cases. (The percentages are based on CDC Nowcast estimates, which provide projections that can change as more data is reported.)

Meanwhile, during the same period, the Centers for Disease Control and Prevention (CDC) reported a significant COVID uptick in several states, based on spikes in emergency room visits and detections of the virus in wastewater. (Wastewater testing can help detect the spread of a COVID in a community.)

Perhaps the biggest question, Dr. Roberts says, is whether the newly mutated virus will continue to evolve before the winter, when infections and hospitalizations usually rise, and if a new fall COVID vaccine will target them.

To better understand how the FLiRT strains emerged, it might help to see how the SARS-CoV-2 virus has changed over time, with new variants forming as mutations emerged in its genetic code. Omicron was a variant of SARS-CoV-2 that took hold in the U.S. in 2021 and began to spawn subvariants of its own. One of those was JN.1, which was identified in September 2023 and spread through the country during the winter months, leading to a spike in COVID hospitalizations. JN.1 also has descendants; the FLiRT subvariants are spinoffs of one called JN.1.11.1.

While more research is needed, experts suspect that the LB.1 strain and another variant called KP.2.3, which also has the two FLiRT mutations plus an additional one, may be more transmissible as well.

But, the fact that the variants are otherwise genetically similar to JN.1 should be reassuring, Dr. Roberts says. "While JN.1 occurred during the winter months, when people gather indoors and the virus is more likely to spread, its symptoms were milder than those caused by variants in the early years of the pandemic," he says.

Other preventive efforts can help. You can avoid getting too close to people who are sick, mask strategically, wash hands properly, improve ventilation, and stay aware of COVID transmission levels where you live and work. Additional strategies are available on the CDC website.

Information provided in Yale Medicine articles is for general informational purposes only. No content in the articles should ever be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider with any questions you have regarding a medical condition.

At the end of March, the KP.2 variant was causing about 4% of infections in the U.S., according to the CDC, while its parental strain, JN.1, was causing over 50% of infections at that time. As of early May, KP.2 makes up about 28% of infections, overtaking JN.1 as the dominant variant.

In this Q&A, Andy Pekosz, PhD, a professor in Molecular Microbiology and Immunology, explains what virologists like him are seeing, whether these variants might cause a summer wave of infections, and how people can protect themselves.

Viruses like SARS-CoV-2 mutate frequently, and when they mutate to evade recognition by antibodies, this often weakens their ability to bind to the cells they want to infect. We then see mutations appear that improve that binding ability. This is a cycle we have seen many times with SARS-CoV-2. The fact that these different variants are picking up the same mutations tells virologists that this combination of mutations is helping the virus accomplish these goals most efficiently.

A JN.1 infection should provide pretty strong protection against all the FLiRT variants. The difference between JN.1 and these variants is only one or two amino acid changes, so there are still a lot of other places antibodies can bind to. Infection from a variant older than JN.1 is less likely to offer as much protection.

And yet, while these waves are becoming smaller, they are still having the greatest impact on our susceptible populations: the elderly, people who are immunocompromised and those with other secondary medical conditions. Everyone can play a role in protecting those populations that remain the highest-risk when new variants cause an uptick in cases.

This is the time of year when governing bodies like the WHO and FDA recommend a formulation for updated COVID vaccines that will roll out in early fall. Last year, the vaccines were based on the XBB.1.5 variant, and only a few months later, the JN.1 variant became the dominant variant in the U.S.

At the end of April, the WHO announced that their COVID vaccine advisory group advises using the JN.1 lineage as the antigen for the upcoming formulations of the vaccine. All of these FLiRT variants are within the JN.1 family of variants.

Here in the U.S., the FDA has postponed its meeting to determine the fall 2024 COVID vaccine from mid-May to early June. That gives them more time to see which of the FLiRT variants is becoming the dominant one so they can fine-tune the WHO recommendation to what they anticipate will be most prominent in the fall.

The period of infectiousness for these FLiRT variants remains the same as with JN.1 and previous omicron variants: After exposure, it may take five or more days before you develop symptoms, though symptoms may appear sooner. You are contagious one to two days before you experience symptoms and a few days after symptoms subside. And as with previous variants, some people may have detectable live virus for up to a week after their symptoms begin, and some may experience rebound symptoms.

Yes, the good news is that Paxlovid is still recommended for high risk individuals. It still works against variants up to JN.1, and based on the sequencing of the FLiRT variants, they should still be susceptible to Paxlovid, as well as to antiviral drugs like molnupiravir and remdesivir. The companies that produce these drugs are always testing them against new variants to ensure they continue to be effective.

Even though KP.2 may be better able to evade immune defenses, most people will experience only mild symptoms because vaccination or prior infection has provided them with sufficient protection to fight off severe illness, according to Dr. Kuppalli.

Peter Chin-Hong, MD, a professor of medicine at the University of California in San Francisco who specializes in infectious diseases, agrees that symptoms so far appear to be similar to those caused by previous recent variants.

AMA Update covers a range of health care topics affecting the lives of physicians, residents, medical students and patients. From private practice and health system leaders to scientists and public health officials, hear from the experts in medicine on COVID-19, medical education, advocacy issues, burnout, vaccines and more.

An in-depth look at the latest wave of respiratory infections sweeping the country. AMA's Vice President of Science, Medicine and Public Health, Andrea Garcia, JD, MPH, discusses trends in COVID, flu and RSV infections, details of the latest COVID variant and the return of mask mandates. Plus, the low use of Paxlovid and deaths linked to the use of hydroxychloroquine to treat COVID during the first wave of the pandemic. AMA Chief Experience Officer Todd Unger hosts.

Unger: Hello and welcome to the AMA Update video and podcast. Today, we have our weekly look at the headlines with the AMA's Vice President of Science, Medicine and Public Health, Andrea Garcia. I'm Todd Unger, AMA's chief experience officer. Welcome back, Andrea. This is our first discussion of the year for 2024.

Garcia: Well, it certainly does feel that way. And if you're not sick, chances are that you know somebody who is. And as we've talked about before, there are disruptions in reporting over the holidays for respiratory viruses. There may be limited appointments for testing. People are traveling and they might not get tested. Or they might use an at-home test, which we know are not reported.

So even with these caveats, there's no doubt that we are seeing a lot of respiratory viruses swirling right now as we continue to see cases of RSV, COVID and flu across the country. According to the CDC, those respiratory illnesses are now elevated in 38 states. Of those, 21 are experiencing very high activity. So that helps explain why it feels like almost everyone is getting sick right now.

Part of this is seasonality. It's an annual trend. It's fueled in part by holiday gatherings, travel, colder weather. And that drives a lot of people indoors, so what we're seeing right now is not entirely unexpected.

Garcia: Yeah, so based on some of the articles, it seems like flu seems to be increasing most dramatically. And CDC says it expects that those numbers are going to be continue to be elevated for several more weeks. We generally do see flu season peak between December and February.

CDC Director Mandy Cohen said she expects this flu season to peak by the end of this month. I think the good news is the flu shot this season is well matched to the strain that we're seeing circulating the most. So there is still time, and it's still worth it to get that vaccine if you haven't yet. Even though cases tend to taper off, we can still see flu circulate well into the spring.

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