New Covid variant: What you need to know about FLiRT, symptoms and a possible summer surge

A new Covid-19 variant is now the dominant strain: KP.2. It’s part of a subset of variants nicknamed “FLiRT,” and a close descendant of JN.1, a subvariant of Omicron. FLiRT made up a small percentage of cases in mid-March to more than a quarter of all Covid cases in the U.S. 

Virologists say FLiRT has some differences in its spike protein that could make it a bit more contagious and tricky for our immune systems to handle than JN.1. Epicenter NYC spoke with Montefiore Medical Center epidemiologist Dr. Inessa Gendlina for advice on staying safe while enjoying summer. 

The interview has been edited and condensed for clarity. 

Is this variant more transmissible?

It’s very similar to JN.1 JN.1 was thought to be a little bit more transmissible than the prior variant. Is FliRT more transmissible? Probably. It appears to be slightly more transmissible, but we don’t yet know and studies are ongoing.  Is it a shorter incubation period? Probably. Overall, we have shifted the incubation period to a shorter time frame, probably somewhere around 3 to 5 days.

Are symptoms more severe for people with FLiRT?

We don’t yet know. It’s likely going to be very similar to JN.1. When the numbers are so low, it’s difficult to make global comments as to the severity of disease. 

Is FLiRT detected by current Covid-19 tests?  

Yes. Testing still remains accurate. 

Are treatments used for previous Covid variants still effective with FLiRT?

All therapeutics continue to be active against JN.1 and KP.2 (FLiRT). There’s no change in how we would treat somebody.  

Is the guidance still that people who have weakened immune systems who get Covid – including FLiRT — they should consider some of these treatments?

Yes. Regardless of the variant, people who are immunocompromised, at high risk, and have severe symptoms should contact their physician and receive treatment for COVID-19.

Does the current vaccine still protect people from this new variant? 

This year’s vaccine — the monovalent Covid vaccine booster that was given starting in September — ended up generating antibodies that were a little less effective against the JN.1 variant than against the original variant that it was made for.  However, the T-cell part of the immune response should remain the same and not be affected by the vaccine’s reduced ability to neutralize currently circulating variants (JN.1 and its children). 

The best immunity is a hybrid immunity from vaccination and from having had an infection. Since most people have been infected in prior waves, people are probably reasonably well-protected, if they have gotten a more recent booster. Even if this booster has a reduced ability to neutralize against the circulating variant, it still adds protection. So there’s still significant protection against severe disease. This is marked by the number of admissions to the hospital, admissions to the ICU, and mortality.

So the most recent booster doesn’t protect people as much as previous variants, but does give some additional level of protection?

Right. It’s no less mismatched against FLiRT than it was against JN.1., which is what we had at the end of the fall.

Is that because even though the mutation has changed, it hasn’t mutated so much that the most current vaccine booster doesn’t have some effect?

Correct. It’s still effective against severe disease. We don’t know if there’s a difference between JN.1 and FLiRT; even with the decreased efficacy of the vaccine, it still is doing what it’s supposed to be doing. This is why the CDC actually made a recommendation for people who are at high risk to get that second booster this season. Because it is continuing to offer significant protection from severe disease.

When you say “this season,” what does that mean exactly?

The CDC suggested that anybody who qualifies—so people over 65 and immunocompromised—if they are more than four months out from their last booster, they should receive the most recent booster this season.

Will recent past infections offer relatively the same protection from FLiRT?

We are still within the same variant family, so a recent infection will continue to offer relative protection from an infection and severe disease in the same timeframe. We usually say about 3 months, 90 days, is when you start losing that protection from a prior infection.

Given everything you said, how worried should New Yorkers be about this variant? 

There’s no reason to worry about this variant specifically. However, I would absolutely recommend being up to date with vaccines and boosters. And certainly following good public hygiene and cough etiquette: hand washing as much as possible, not coming to work if people are feeling sick, testing and avoiding exposing others if they have symptoms or test positive for Covid.

Should people be concerned about the potential for long Covid symptoms with this variant?

We don’t yet know the FLiRT variant’s long-term impact, but based on what we saw with JN.1, we don’t expect any additional long-term sequelae.

Are there any signs of a summer surge right now? 

Not yet. I will say that our most accurate means of knowing if there’s a surge or the numbers are going up is actually wastewater surveillance. So I keep a close eye on wastewater surveillance, and that’s really our early indicator of how much Covid there is in the community. That’s where water treatment facilities actually test the water that’s going through the facilities and where that water came from. You can find it on the New York State Department of Health website. CDC tracks that as well.

We are watching for a summer surge like we’ve had in the last couple of years — not as big as our full winter surge, but certainly a bump in the summer.

So while we’re watching, I certainly encourage people to be careful, wash their hands, mask, not come to work, not expose others if they have any symptoms, and certainly test. But there’s nothing particularly specific to this variant compared to the previous ones.

Many people this time of year are going to graduation or planning end-of-year parties and gatherings. Should this variant be a concern at all?

This would be no different than previous concerns. People who are immunocompromised or vulnerable should wear masks. Again, I recommend masking in areas of concern—aggregate group environments with poor ventilation or if there’s a concern about coming in contact with people with symptoms.

So that would include subways, big graduation parties or ceremonies?

Crowded enclosed spaces with suboptimal or poor ventilation. Graduation or private parties are a little more challenging to make masking recommendations —  those are usually large spaces, people are outdoors. But with any indoor spaces with lots of crowding, lots of people, and not great air exchanges or ventilation, like subways, I would absolutely recommend wearing a mask. 

I would say people should mask in crowds, but I think we have to be cognizant of what is a realistic ask.

Where should everyday New Yorkers be looking to see how prevalent the FLiRT variant is at any given point? 

The city displays the percentage of variants. And the CDC has a pretty accurate way of showing where we have been, and showing the trends and evolution of the variants. FLiRT seems to be gaining traction — Right now, it’s 23% for New York City. Of the sequenced variants, the percentage of those being FLiRT is on the rise. But we are not yet seeing the next wave of Covid. So it’s important to take both of those in the context of, ‘is there a shift in the type of variant we’re seeing? Yes. Is it, overall, significant for epidemiology and how we act on it? Unclear just yet.

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