XFG & Other COVID-19 Variants: How They’re Changing the Game

COVID-19 has evolved since it first emerged in 2019. As the virus spreads, it mutates — creating new versions called “variants.” Some of these variants fade away; others dominate and change how we prevent, treat, and manage COVID-19.

Let’s walk through the main variants we’ve known so far, what makes them different, and what you should know in 2025.

What Is a “Variant” Anyway?

Every time a virus replicates (makes copies of itself), there’s a chance for small changes, aka mutations. Most mutations don’t do much, but sometimes they give the virus an advantage — maybe it spreads more easily, evades immunity better, or causes different symptoms.

Health organizations like the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC) monitor these. They classify variants as:

• Variants of Concern (VOCs): Major changes, like increased transmissibility or severity.

• Variants of Interest (VOIs): Less severe or less widespread, but potentially important.

• Variants Under Monitoring / Under Investigation: Being tracked because they show some new features.

Knowing which variant is circulating helps governments and health systems decide on public health measures, vaccines, and treatments.

The Big Players: COVID-19 Variants to Know

Here are the major COVID-19 variants that have made headlines over the years, and what happened with them.

Alpha (B.1.1.7)
Was one of the first globally dominant strains; eventually overtaken by Delta.

Beta (B.1.351)
Still a concern but never became dominant globally like Omicron or Delta.

Gamma (P.1)
Had local waves; gradually replaced by more transmissible variants.

Delta (B.1.617.2)
Dominant in many countries during 2021. Vaccines worked, but breakthrough infections more common.

Omicron (B.1.1.529)
Became dominant globally. Gave rise to many subvariants.

Subvariants: The Omicron Family & Recent Variants

Omicron spawned a large family of subvariants. Some are more transmissible, others better at evading immunity, but most do not cause worse disease in people with good vaccination or prior infection. Here are some recent ones worth knowing:

• JN.1 — One of the significant subvariants circulating in 2024-2025.

• BA.2.86 (nicknamed “Pirola”) — Notable for having many mutations. WHO has flagged it as a “variant under monitoring.”

• NB.1.8.1 — A newer lineage showing up in sequencing data; being watched for its growth and immune evasion characteristics.

• KP.3.1.1, XEC, LP.8.1 — These are sub-lineages of the Omicron/JN.1 family that health authorities are keeping an eye on because they’re circulating more.

The XFG Variant (Stratus)

One of the newest names you might hear is XFG, also called Stratus. “Stratus” appears to be a nickname used by some media and scientists for XFG. The nickname helps simplify communication with the public, but “XFG” is the technical or scientific label. Learn more about the Stratus Variant or XFG Variant here.

The XFG variant is a recombinant strain, meaning it formed when two earlier versions of the virus combined. The World Health Organization currently classifies XFG as a Variant Under Monitoring (VUM)—it has spread to multiple countries, but so far the global risk is considered low. There’s no evidence that it causes more severe illness than other circulating variants, and vaccines are still expected to provide protection against serious disease. Still, its gradual growth and unique mutations mean scientists are watching it closely.

How Do New Variants Change Things?

Every time you hear about a “new COVID variant,” it can feel worrying—but what does that really mean? Variants aren’t entirely new viruses; they’re versions of the same coronavirus that have picked up mutations. Sometimes those mutations don’t change much, but other times, they shift the way the virus behaves.

Here are the main things that can change when new variants appear:

• Spread / Transmissibility: Some variants are simply better at moving from person to person. That’s why Delta spread so quickly, and why Omicron raced across the globe in weeks. When a variant spreads more easily, even if it doesn’t cause more severe illness, it can still lead to a surge in cases.

• Immune Evasion: This is when the virus finds ways to “sneak past” the protection we’ve built up from vaccines or past infections. It doesn’t mean vaccines stop working—they still protect against severe illness—but it can mean more mild or moderate breakthrough cases.

• Severity of Illness: Not all variants are equally harsh. Delta, for example, was linked to more severe illness in some studies, while Omicron, on average, caused milder symptoms in vaccinated people. But remember, even a “milder” variant can overwhelm hospitals if lots of people get sick at once.

• Symptoms: New variants sometimes bring subtle changes in how people feel. With Omicron and its subvariants, many reported more sore throats and congestion, and fewer cases of the classic “loss of smell” seen early in the pandemic. These shifts can make it harder to recognize COVID right away.

• Vaccine & Treatment Effectiveness: Some variants affect how well our tools work. For example, certain monoclonal antibody treatments that were effective early on no longer worked against Omicron. That’s why vaccines are updated from time to time—to stay one step ahead of the virus.

In short, variants remind us that the virus is still evolving. Most of the time, the changes are manageable, especially with vaccines and good public health measures. But keeping an eye on them helps scientists and health officials adjust strategies, whether that’s updating vaccines, recommending boosters, or changing treatment plans.

Why Variants Are Named the Way They Are

If you’ve heard terms like “Alpha,” “Delta,” “Omicron,” or “BA.2.86,” here’s what they mean:

• WHO uses Greek letters for major variants of concern (Alpha, Beta, Gamma, Delta, Omicron) to avoid stigma.

• Scientific names are more technical (e.g. B.1.1.529 for Omicron). Subvariants often have codes like BA, BQ, NB, etc.

• Some variants also get informal “nicknames” in media or online, but those aren’t official unless WHO or public health agencies accept them.

What’s the Current Situation (2025)?

As of mid-2025:

• Omicron and its descendants remain the main players globally.

• Some subvariants like JN.1, BA.2.86, NB.1.8.1, XFG are under monitoring due to their ability to spread and potential immune escape.

• No major new variant has yet shown overwhelming danger compared to Omicron (in terms of severity) in vaccinated populations. But cases may flare up if immunity wanes or against populations with low vaccination.

What You Can Do to Stay Protected

Knowing variants is helpful, but what really matters is how you protect yourself. Here are some best practices:

1. Stay up to date with vaccinations and boosters — Vaccines still work best against severe illness, hospitalization, and death.

2. Wear masks in crowded or poorly ventilated places if there’s a surge locally.

3. Wash hands and practice good hygiene. Stay home if you feel sick.

4. Keep an eye on local public health advisories — they’ll often alert you if a concerning variant is spreading nearby.

5. Get tested if symptoms develop. Treatment and isolation can reduce spread.

What We Don’t Yet Know

Science has learned a lot about variants, but there are still unanswered questions:

• Which subvariant might become dominant next?

• Will some variants develop resistance not just to vaccines, but to all antibody therapies?

• How much will the virus keep evolving in vaccinated vs unvaccinated populations?

• Could severity increase under certain conditions (e.g. for certain vulnerable groups)?

Researchers continue to monitor variants through genomic surveillance (sequencing virus samples), global reporting, and lab studies to see how variants behave.

FAQs — Variants Edition

Q1: Are new variants worse than older ones?
Sometimes certain aspects (like spread or immune escape) are “worse,” but not always more severe. For many Omicron subvariants, even if more people get infected, most vaccinated folks don’t get very sick.

Q2: Do I need different vaccines for each variant?
Not usually. Updated boosters are often designed to cover multiple strains. Health authorities will approve boosters when needed.

Q3: Can I get reinfected by a new variant even if I already had COVID-19?
Yes — new subvariants can sometimes bypass past immunity, especially if past infection was from a different variant. But that past immunity often still gives good protection against severe disease.

Q4: Do masks still work if a new variant shows up?
Yes. Masks help reduce spread of respiratory droplets no matter the variant. Choosing good quality masks (e.g. N95, KN95) helps more.

Final Thoughts

Variants are part of the normal evolution of viruses. COVID-19 keeps mutating, but many of these changes don’t drastically alter how we prevent or treat the disease — especially when vaccines, good hygiene, and health awareness are in place.

The important takeaway is this: stay informed, follow public health guidance, keep up with vaccinations, and do the basics well. It’s those everyday habits that matter most in keeping you safe, even as the virus changes.

Related Articles:
1. Summer COVID-19 Update: Stratus Variant & Rising US Cases
2. New COVID Variant NB.1.8.1: How Dangerous Is It? Symptoms, Transmission and Updates
3. COVID-19 Vaccines: What You Need to Know (And Why It Still Matters)

Sources:

1. World Health Organization (WHO) – COVID-19 Variants Dashboard
   https://data.who.int/dashboards/covid19/variants datadot

2. WHO – Tracking SARS-CoV-2 Variants
   https://www.who.int/activities/tracking-SARS-CoV-2-variants World Health Organization

3. Centers for Disease Control and Prevention (CDC) – Variants and Genomic Surveillance
   https://www.cdc.gov/covid/php/variants/variants-and-genomic-surveillance.html CDC

4. CDC – SARS-CoV-2 Variant XEC Increases as KP.3.1.1 Slows
   https://www.cdc.gov/ncird/whats-new/sars-cov-2-variant-xec-increases-as-kp-3-1-1-slows.html CDC

5. Mayo Clinic – COVID-19 Variants: What’s the Concern?
   https://www.mayoclinic.org/diseases-conditions/coronavirus/expert-answers/covid-variant/faq-20505779 Mayo Clinic

6. Gavi (Vaccine Alliance) – What You Need to Know About the New “Nimbus” (NB.1.8.1) and “Stratus” Variants
   https://www.gavi.org/vaccineswork/eight-things-you-need-know-about-new-nimbus-and-stratus-covid-variants Gavi

7. Health Stony Brook Medicine – Understanding COVID-19 Variant Stratus (XFG)
   https://health.stonybrookmedicine.edu/understanding-covid-19-variant-stratus-what-you-need-to-know/ Stony Brook Medicine Health News

8. UNMC Health Security – What to know about the new COVID-19 variant XFG
   https://www.unmc.edu/healthsecurity/transmission/2025/07/08/what-to-know-about-the-new-covid-19-variant-xfg/