11 Top COVID FLiRT and LB.1 Symptoms, According to Experts

Just when everyone thought they had finally learned the alphabet of COVID variants, along came FLiRT and LB.1 to make things sound less like a virus family tree and more like a dating app glitch. The good news is that experts have been pretty consistent about one important point: these variants did not suddenly invent a brand-new symptom checklist. In most cases, FLiRT and LB.1 looked a lot like other recent Omicron-descended infectionsannoying, contagious, and often surprisingly similar to a bad cold, a rough flu, or a “why do I feel like I got hit by a truck and also swallowed sandpaper?” kind of week.

That matters because people often assume a new variant must come with dramatic new warning signs. Not necessarily. Infectious disease experts have repeatedly said that FLiRT and LB.1 symptoms are mostly familiar, especially upper-respiratory symptoms such as sore throat, cough, congestion, fever, and fatigue. Some people also report gastrointestinal issues like nausea or diarrhea. And while loss of taste or smell can still happen, many experts say it appears less common now than it was in earlier phases of the pandemic.

If you are looking for the top COVID FLiRT and LB.1 symptoms, think less “mystery illness from a sci-fi movie” and more “the cold from hell that also ruins your energy level.” Here is what experts want you to watch for.

What Are FLiRT and LB.1, Exactly?

FLiRT is a nickname used for a group of Omicron-related subvariants, including strains such as KP.2 and KP.3. LB.1 is closely related and drew attention because it carried an additional mutation. Despite the dramatic headlines, experts said the bigger concern was usually transmissibility and immune escape, not a radically different symptom pattern.

In plain English: FLiRT and LB.1 were good at spreading, but they generally caused the same types of illness patterns doctors had already been seeing with other recent COVID infections. Your symptoms could still vary a lot depending on your age, vaccination history, prior infections, underlying conditions, and plain old bad luck.

11 Top COVID FLiRT and LB.1 Symptoms

1. Sore Throat

A sore throat has been one of the most commonly reported symptoms with FLiRT and LB.1 infections. For many people, it shows up early and can feel mild at firstjust enough to make you clear your throat every five secondsbefore becoming more noticeable by the next day. Some people describe it as scratchy; others say it feels like they swallowed hot toast crusts. Not elegant, but accurate.

This symptom matters because many people dismiss it as allergies, dry air, or “sleeping with the fan on.” Experts say that if a sore throat appears with fatigue, fever, congestion, or cough, COVID should absolutely be on your radar.

2. Cough

Cough remains one of the signature COVID symptoms, including with FLiRT and LB.1. It may start dry, stay dry, or become more productive as congestion builds. In many recent cases, doctors have described COVID as acting like an upper-respiratory infection, so the cough may feel more like persistent throat and chest irritation than the deep lung symptoms people feared early in the pandemic.

That said, not every cough is the same. A mild tickle is different from a cough that keeps you up at night, leaves you short of breath, or causes chest pain. When the cough is intense or paired with trouble breathing, that is when it moves from “annoying” to “please call a medical professional.”

3. Congestion or Runny Nose

If FLiRT and LB.1 had a calling card, it was often the classic cold-like combo of stuffy nose, runny nose, and sinus pressure. Experts repeatedly noted that many patients felt like they had a bad cold rather than the distinct symptom pattern people once associated with COVID.

This can make COVID harder to spot without testing. A runny nose used to make people think “seasonal allergies” or “just a cold.” Now it belongs on the COVID symptom list too. If your nose is suddenly acting like it is training for a marathon and you also feel wiped out, test yourself instead of assuming it is nothing.

4. Fever

Fever is still a top symptom, even if not everyone gets it. Some people spike a clear temperature early. Others feel hot, achy, and “feverish” before the thermometer fully cooperates. Fever is your body’s immune system waving a giant flag that says, “Something is definitely up.”

Experts also remind people that fever can come and go. One decent afternoon does not always mean the virus packed its bags and moved out. If you feel better for a bit and then get walloped again by fever or chills, that is not unusual.

5. Chills

Chills often show up alongside fever, but they can also arrive before a fever is obvious. You may feel cold in a warm room, pile on a blanket, and still feel like your bones are shivering out a protest letter. Chills are common with many viral infections, and COVID is no exception.

With FLiRT and LB.1, experts often grouped chills with fever, body aches, and fatigue. That cluster can make the illness feel more flu-like, especially in the first couple of days.

6. Fatigue

Fatigue is one of the sneakiest symptoms because it can be easy to underestimate. This is not always ordinary tiredness. Many people describe COVID fatigue as the kind of exhaustion that makes simple tasks feel strangely expensive. Replying to a text? Maybe later. Walking upstairs? Why is there a mountain in my house?

Experts say fatigue can hit early, linger after the worst symptoms fade, and vary wildly from person to person. Some people mostly feel congested; others feel like their battery dropped to 8% and refuses to charge.

7. Headache

Headaches remain a frequent complaint with COVID, including during the FLiRT and LB.1 waves. Sometimes the headache feels dull and pressure-like, especially if congestion is part of the picture. Other times it can feel more intense and body-wide, as if your whole nervous system is asking for a day off.

A headache by itself is not very specific, of course. But a headache paired with sore throat, fatigue, cough, fever, or stomach symptoms becomes much more suspicious. Experts often mention headache as part of the broader “viral misery sampler pack.”

8. Muscle or Body Aches

Body aches are another common symptom that can make COVID feel more like the flu than the common cold. You may feel soreness in the back, legs, shoulders, or everywhere all at once. Some people say it feels like they worked out too hard. Others say it feels like they got into a disagreement with gravity and lost.

Muscle aches are especially common when fever and chills are also present. For people with recent FLiRT- or LB.1-type infections, this symptom often adds to the sense that the illness is systemic, not just a nose-and-throat issue.

9. Shortness of Breath or Difficulty Breathing

Shortness of breath is still one of the most important symptoms to take seriously. Experts continue to list it as a possible COVID symptom, even though many FLiRT and LB.1 infections were described as milder and more upper-respiratory than earlier pandemic strains.

This symptom deserves extra attention because it can signal more significant illness. If you are struggling to catch your breath, breathing faster than usual, or feeling chest tightness that does not improve, do not tough it out just to prove you are “fine.” That is the kind of symptom that warrants prompt medical advice, especially for older adults, pregnant people, and anyone with underlying health conditions.

10. Nausea or Vomiting

COVID may be a respiratory virus, but it has never fully respected departmental boundaries. Nausea and vomiting can still happen, and experts specifically noted that gastrointestinal symptoms sometimes appear with FLiRT and LB.1 as well.

These symptoms can be easy to misread as food poisoning or a random stomach bug, especially if respiratory symptoms have not started yet. But if nausea shows up with fever, headache, fatigue, cough, or sore throat, COVID belongs on the suspect list.

11. Diarrhea

Diarrhea rounds out the list of top symptoms experts continue to mention. It is not always the headline symptom, but it is common enough that it should not be ignored. In some cases, diarrhea shows up early. In others, it joins the party later, because apparently COVID enjoys being an overachiever.

When diarrhea happens with dehydration, weakness, fever, or trouble keeping fluids down, it becomes more than an inconvenience. That is especially important for kids, older adults, and anyone already vulnerable to dehydration.

What About Loss of Taste or Smell?

Yes, it still deserves a mention. Loss of taste or smell remains on the official COVID symptom list, and it can still happen with FLiRT and LB.1. However, many experts say it appears less common now than it was in earlier stages of the pandemic. So if you do not lose your sense of smell, that does not rule out COVID. And if you do suddenly realize your coffee tastes like warm disappointment, it is definitely time to test.

Why FLiRT and LB.1 Symptoms Can Be Confusing

One reason these variants caused so much confusion is that they often looked like other routine respiratory illnesses. A bad cold, mild flu, allergies, RSV, and COVID can overlap more than people like to admit. Experts say symptoms also vary from one infection to the next, even in the same person. You may have had COVID once with a fever and body aches, then get reinfected later and mostly have sore throat and fatigue.

That is why symptoms alone cannot tell you which variant you have. In fact, they cannot even confirm whether it is COVID at all. Home tests can tell you if you likely have COVID, but they do not identify whether the culprit is FLiRT, LB.1, or another subvariant. Determining the exact variant requires genomic sequencing, which is not part of a regular home testing experience in your kitchen.

When to Test, Rest, and Reach Out for Help

If you develop symptoms that fit the COVID patternespecially sore throat, cough, congestion, fatigue, fever, body aches, or GI symptomsexperts recommend testing as soon as appropriate and taking sensible precautions. Stay home and away from others while you are sick, especially if symptoms are worsening or you have a fever. Return to normal activities only after your symptoms are improving overall and you have been fever-free for at least 24 hours without fever-reducing medicine.

High-risk people should not wait too long to contact a clinician. Treatments such as antivirals are most helpful when started early. If you are older, immunocompromised, pregnant, or living with conditions such as asthma, heart disease, diabetes, obesity, or chronic lung disease, early medical advice matters.

Seek urgent medical attention if you have trouble breathing, chest pain or pressure, new confusion, blue or gray lips or skin, or difficulty staying awake. A “mild variant” does not mean every case is mild.

Experiences People Commonly Report With FLiRT and LB.1

Many people who got sick during the FLiRT and LB.1 waves described the illness as strangely familiar but annoyingly unpredictable. One common experience was the “it’s just a cold… wait, maybe not” pattern. The illness might start with a sore throat or runny nose so ordinary that people barely noticed it. Then, by the next day, fatigue hit hard, the cough kicked in, and suddenly the situation felt less like mild inconvenience and more like the body had quietly filed an official complaint.

Another frequent experience was the energy crash. People did not always feel dramatically sick in a movie-worthy way, but they felt off in a way that made regular life harder. They could still walk around the house, answer emails, or make lunch, but everything felt slower and heavier. This is one reason some people underestimate COVID at first. If you can still function, you may assume you are fine. Then you try doing normal tasks and realize your body did not get that memo.

Some people reported the “cold plus stomach issue” experience, which felt especially confusing. They had congestion, cough, or sore throat, but also nausea or diarrhea. That combination made them wonder whether they had two different bugs at once. Experts have long said COVID can affect both the respiratory tract and the gastrointestinal system, and FLiRT/LB.1-era experiences fit that pattern.

There was also the reinfection surprise. People who had COVID before sometimes expected the next infection to feel exactly the same. It often did not. One infection might feature fever and body aches, while another brought mostly headache, throat pain, and exhaustion. That difference caused some people to rule out COVID too quickly because it “didn’t feel like last time.” Experts have been clear that symptom order, severity, and combinations can shift from case to case.

A final common experience was the lingering “ugh” phase. Even after the fever faded or the worst congestion improved, people often described several extra days of tiredness, brain fog, disrupted sleep, or reduced stamina. They were technically better, but not exactly ready to sprint through life like a motivational speaker in running shoes. That in-between stage matters because pushing too hard too fast can leave people feeling worse. Rest, hydration, and patience are not glamorous, but they are still useful.

In other words, the real-world experience of FLiRT and LB.1 often matched what experts were saying all along: the symptoms were usually familiar, the presentation could vary, and the smartest move was to take suspicious symptoms seriously instead of trying to out-stubborn a virus.

Final Takeaway

The biggest expert takeaway on COVID FLiRT and LB.1 symptoms is refreshingly un-dramatic: these variants generally caused the same types of symptoms doctors had already been seeing with recent Omicron-related COVID infections. The top symptoms included sore throat, cough, congestion, fever, chills, fatigue, headache, body aches, shortness of breath, nausea or vomiting, and diarrhea, with loss of taste or smell still possible but often less prominent.

So no, FLiRT and LB.1 did not rewrite the rulebook. They mostly reminded everyone that COVID is still very good at pretending to be “just a cold” until it is not. When symptoms line up, test. When you are sick, rest. And when breathing gets harder or the illness hits someone high-risk, get medical help early. Not very glamorous advice, perhapsbut still much more useful than arguing with your thermometer.