Another summer, another COVID warning. Health officials and The World Health Organization (WHO) are reporting that the new Omicron subvariant of COVID‑19, known as NB.1.8.1 or "Nimbus," is spreading rapidly across the U.S. The strain now accounts for roughly 37% of all reported COVID-19 diagnoses reported nationwide between May 25 and June 7, according to the CDC, making it the second most common strain in the U.S. this summer. So far, fourteen states have been hit the hardest.

Here's what health experts are saying about Nimbus, its symptoms, and how to stay safe and healthy this summer.

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Where Nimbus Is Spreading

As we've previously reported, the WHO first detected NB.1.8.1, a SARS-CoV-2 variant, in China in January 2025. Its U.S. arrival was traced back to international travelers arriving at airports as early as late March.

In a May 23 report, the WHO officially labeled Nimbus as a "variant under monitoring."

"NB.1.8.1 is growing rapidly compared to co-circulating variants," the WHO wrote in its report. It quickly overpowered previous variants due to a mutation-driven growth advantage, increasing from 2.5% to 10.7% of global samples in 22 countries in just four weeks.

However, the overall severity of the variant has been marked as low.

"Despite a concurrent increase in cases and hospitalizations in some countries where NB.1.8.1 is widespread, current data do not indicate that this variant leads to more severe illness than other variants in circulation," the WHO stated.

Still, that hasn't stopped Nimbus from becoming a widespread health issue.

As of June 13, NB.1.8.1 has been reported in 14 states:

• Arizona
• California
• Colorado
• New Jersey
• New York
• Hawaii
• Illinois
• Maryland
• Massachusetts
• Ohio
• Rhode Island
• Vermont
• Virginia
• Washington

According to the CDC, Nimbus now represents over one-third of COVID cases in the U.S., making it the second most common strain behind LP.8.1, the dominant variant behind 38% of U.S. cases.

Despite this spread, hospitalizations and deaths remain steady, and vaccines continue to protect against serious complications.

Symptoms to Watch For

Nimbus has been nicknamed the "razor blade" variant due to patients reporting a severe sore throat that feels like swallowing sharp metal objects.

However, health officials say that, while this particularly brutal symptom is very common with this strain, it's not new.

In fact, Nimus symptoms closely mirror those of prior Omicron strains, and include:

• Fever
• Fatigue
• Cough
• Congestion
• Sore throat
• Muscle or body aches
• Headache
• Nausea or vomiting
• Diarrhea
• Loss of taste or smell

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How to Stay Safe

Even though the severity of Nimbus hospitalizations remains low, stay on top of your health and be on the lookout for any potential COVID-like symptoms.

To protect yourself, experts recommend staying up-to-date with your COVID vaccinations, as they still protect against serious illness caused by COVID strains.

You can also choose to wear a mask in public indoor spaces to slow the spread.

If you feel sick—especially with a severe sore throat or flu-like symptoms, take a COVID test and call your doctor.

Finally, make sure you're always practicing good hygiene. Wash your hands often and regularly to prevent the spread of germs and stay home if you're not feeling well.

As health officials note, COVID and its new variants are a persistent and unfortunate reality we have to live with, but there are steps you can take to keep yourself safe and healthy all year long.