A new subvariant of COVID-19, officially named NB.1.8.1 and nicknamed ‘Nimbus’, has become the most widespread strain in the United States, according to the Centers for Disease Control and Prevention (CDC).
First Detected in March, Now Leading U.S. Cases
Initially spotted in March through the CDC’s airport surveillance program, which collects nasal swabs and wastewater samples, Nimbus has rapidly gained ground across several states since June. By the end of a two-week period ending June 21, it accounted for 43% of all COVID-19 cases nationwide. Current estimates suggest it makes up anywhere from 13% to 68% of circulating strains, according to the Department of Health and Human Services (HHS).
However, experts like Rajendram Rajnarayanan, a scientist at the New York Institute of Technology, caution that actual figures could be unreliable due to “limited surveillance.”
Where It’s Been Found
The variant has already been detected in U.S. states including California, New York, Virginia, and Washington, as well as internationally in countries like Australia and the United Kingdom. The strain is a subvariant of Omicron and is believed to have originated in China earlier in 2025, later spreading across parts of Asia and Europe, Bloomberg reported.
Symptoms and Severity
People infected with the Nimbus variant have described a distinct symptom — intense throat scratchiness, likened to “razor blades in the throat.” Other common symptoms include:
- Nasal congestion
- Fatigue
- Mild cough
- Fever
- Loss of taste or smell
- Runny nose
- Loss of appetite
- Muscle aches
Despite its growing prevalence, the World Health Organization (WHO) has stated that the public health risk posed by Nimbus is not greater than previous variants.
Ongoing Monitoring
The CDC continues to monitor the variant’s spread through its airport screening program, using both nasal and wastewater samples to track infections. Officials say they are “aware of increasing detections” but have not issued any changes to existing public health guidance.
As the U.S. heads into the latter half of 2025, health authorities are urging continued vigilance, especially with evolving strains like Nimbus gaining ground across states and borders.
