XBB COVID-19 ‘Nightmare Variant’: What You Need to Know About Symptoms, Risks, and Protection
Understanding its rapid spread and immune escape reveals how to strengthen your defenses.
The COVID-19 pandemic has experienced many twists and turns, with new variants of the virus SARS-CoV-2 continuing to emerge. Among the most concerning is the XBB variant, sometimes dubbed the ‘nightmare variant’ due to its rapid spread and increased resistance to immunity. In this article, we break down what makes XBB unique, the symptoms associated with it, who is most at risk, and what public health experts recommend now.
Contents
- What Is the XBB COVID-19 Variant?
- Why Is XBB Called the ‘Nightmare Variant’?
- Symptoms of the XBB Variant
- Who Is Most at Risk from XBB?
- Testing and Diagnosing XBB Infection
- How to Protect Yourself Against XBB
- Expert Guidance and Recommendations
- Frequently Asked Questions (FAQs)
What Is the XBB COVID-19 Variant?
XBB is a recombinant subvariant of Omicron, meaning it is the result of two distinct subvariants combining their genetic material. Belonging to the Omicron lineage of the SARS-CoV-2 virus, XBB has rapidly become one of the most dominant strains in the United States and over 70 other countries.
The specific subvariant XBB.1.5, first identified in the U.S. in late 2022, has drawn particular attention. Its unique mutations give it a substantial growth advantage over earlier variants and enable it to evade many of the antibodies developed from vaccines or previous infection. According to the Centers for Disease Control and Prevention (CDC), XBB.1.5 quickly rose to account for a significant percentage of new COVID-19 cases, especially in the Northeast.
Why Is XBB Called the ‘Nightmare Variant’?
The nickname ‘nightmare variant’ has been used by some experts and media due to a combination of the following factors:
- Rapid and efficient transmission: XBB and its subvariants, especially XBB.1.5, have mutations that enhance their ability to bind to human cell receptors, resulting in a higher transmission rate compared to prior Omicron lineages.
- Immune evasion: Laboratory studies show XBB can evade antibodies generated from earlier COVID-19 infections and vaccines. In effect, the variant can infect people who were previously considered protected, increasing the risk of reinfection.
- Widespread impact: XBB led to increased case counts in affected regions and caused a notable uptick in hospitalizations, for instance in parts of New York City.
- Unknowns about severity: While early evidence does not clearly point to XBB causing more severe illness, its widespread reach means even a small percentage of severe cases could lead to significant impacts at the population level.
What Sets XBB Apart?
The XBB variant’s spike protein has unique mutations that enhance its ability to invade human cells. For example, the Ser486Pro mutation, observed notably in XBB.1.5, is linked to increased binding strength to the ACE2 receptor, which is essential for viral entry into cells. This combination of increased infectivity and immune escape underscores why XBB is monitored so closely.
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Symptoms of the XBB Variant
Symptoms caused by XBB generally resemble those of other Omicron subvariants but can vary in intensity and presentation. According to medical experts and the CDC, the most reported symptoms of XBB infection are:
- Fever or chills
- Cough
- Sore throat—may feel especially severe or described as “razor blade throat”
- Headache
- Blocked or runny nose
- Shortness of breath or difficulty breathing
- Body or muscle aches
- Fatigue
- Nausea or vomiting
- Loss of taste or smell
Some unique presentations for newer Omicron subvariants, such as XBB, include heightened throat pain (described as ‘razor blade throat’), and rarely, conjunctivitis (red, watery, itchy eyes), which has been highlighted in sibling strains such as XBB.1.16 (‘Arcturus’).
| Symptom | Original COVID-19 | Omicron/XBB |
|---|---|---|
| Sore Throat | Sometimes | Common (May be severe) |
| Nasal Congestion | Common | Common |
| Cough | Common | Common |
| Fever | Very Common | Common |
| Fatigue | Very Common | Common |
| Loss of Smell/Taste | Often Present | Less Common |
| Conjunctivitis | Rare | Sometimes (Arcturus/XBB.1.16) |
| Shortness of Breath | Common | Occasionally |
When Should You Seek Emergency Medical Attention?
- Difficulty breathing
- Persistent chest pain or pressure
- New confusion
- Inability to wake or stay awake
- Blue, pale, or gray skin, lips, or nail beds (especially for people with darker skin tones)
Any of the above symptoms merit urgent medical attention. Contact emergency services or your healthcare provider immediately if you notice these signs in yourself or loved ones.
Who Is Most at Risk from XBB?
While anyone can contract XBB, some groups remain at greatest risk for developing severe illness:
- Older adults, especially age 65 and older
- People with underlying health conditions (heart, lung, kidney, diabetes, immune-compromising diseases)
- Pregnant individuals
- People living in congregate settings (e.g., nursing homes, correctional facilities)
- People who are unvaccinated or have not received recent boosters
As the variant can evade immunity from previous infections and even vaccination to some degree, everyone should remain cautious—especially as protection from infection wanes over time.
Testing and Diagnosing XBB Infection
XBB is detected using standard COVID-19 PCR and rapid antigen tests, though only specialized laboratory sequencing can specify the exact variant. If you have symptoms consistent with COVID-19 or have been exposed to someone who has tested positive, get tested as soon as possible. Self-isolate until you have results, and follow the latest guidance from local health authorities and the CDC.
How to Protect Yourself Against XBB
Despite its increased ability to evade antibodies, getting vaccinated and staying up to date on booster shots remains one of the most effective steps you can take to reduce the risk of serious disease and hospitalization. The CDC and World Health Organization strongly recommend everyone eligible receive the latest COVID-19 vaccines and boosters, especially with the ongoing spread of XBB and related subvariants.
Other Protective Strategies
- Wear a high-quality mask (such as N95 or KN95) in crowded or indoor public places, especially during periods of high transmission.
- Increase indoor ventilation where possible.
- Practice regular hand hygiene by washing hands thoroughly and using hand sanitizer when appropriate.
- If sick, stay home and avoid contact with vulnerable individuals.
- Test frequently, especially after possible exposure, or before gathering with high-risk individuals.
While no vaccine or protective measure is entirely foolproof, consistent adherence to these strategies can meaningfully reduce your personal and community risk.
Expert Guidance and Recommendations
Health authorities, including the CDC and infectious disease experts, continue to emphasize the importance of public health fundamentals, especially in light of variants like XBB:
- Vaccination and boosters offer meaningful protection against severe disease, even for evolving strains.
- Isolation and quarantine guidelines should be followed carefully if you test positive.
- Keep up to date with the latest public health recommendations, including mask mandates and event guidance, as these may change rapidly.
Experts warn that, as XBB is extremely transmissible, even small lapses in prevention can cause large outbreaks, especially among susceptible populations.
Frequently Asked Questions (FAQs) About the XBB ‘Nightmare Variant’
Q: What is the XBB ‘nightmare variant’ and how did it emerge?
A: XBB is a recombinant subvariant of Omicron. It emerged through the genetic combination of two Omicron lineages and has spread rapidly due to its mutations enhancing transmission and immune escape.
Q: Is XBB more dangerous than previous COVID-19 variants?
A: XBB is more transmissible and better at evading immunity from past infection or vaccination, but current data do not show it causes more severe disease than previous variants. However, its high spread means more individuals are at risk, which can result in higher hospitalizations.
Q: Does the COVID-19 vaccine protect against XBB?
A: While XBB has shown some capacity to evade antibody responses, COVID-19 vaccines, especially when boosted, continue to provide significant protection against severe illness, hospitalization, and death. Newer vaccine formulations are being studied for even stronger protection.
Q: What are the earliest warning signs of an XBB infection?
A: The most common early symptoms are sore throat, nasal congestion, headache, and fatigue. The sore throat can be unusually severe (sometimes termed ‘razor blade throat’).
Q: What steps should I take if I test positive for COVID-19?
A: Isolate from others for at least five days, follow CDC guidelines, alert close contacts, monitor your symptoms, and seek medical help if symptoms are severe.
Key Takeaways
- The XBB ‘nightmare variant’ presents new challenges due to its rapid spread and antibody evasion.
- Symptoms closely mirror previous Omicron strains but can be more pronounced in the throat.
- Vaccines and preventive health measures remain crucial to reducing serious illness and community spread.
References
- https://pmc.ncbi.nlm.nih.gov/articles/PMC10152970/
- https://www.usatoday.com/story/news/health/2025/06/23/new-covid-variant-2025-symptoms/84317260007/
- https://ada.com/covid/arcturus-covid-19-variant/
- https://www.nebraskamed.com/COVID/what-covid-19-variants-are-going-around
- https://www.ecdc.europa.eu/en/covid-19/variants-concern
- https://www.who.int/activities/tracking-SARS-CoV-2-variants
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