New COVID-19 Variant Nimbus Spreads in U.S. Amid Travel Season

New York City, NY — A new COVID-19 variant, known as NB.1.8.1 or “Nimbus,” is spreading rapidly across the United States during the peak travel season. This variant, a mutated version of the omicron subvariant, has been linked to surges in China and parts of Asia in spring 2025. By June 7, it accounted for an estimated 37% of COVID cases in the country.

According to the Centers for Disease Control and Prevention (CDC), NB.1.8.1 was first detected in late March 2025 through airport screening programs. It has since been reported in more than a dozen states, and experts predict cases will likely continue to rise. On May 23, the CDC classified Nimbus as a “variant under monitoring” due to its rapid spread and specific mutations that could affect its transmissibility.

While NB.1.8.1 is increasing its share of COVID-19 cases, overall COVID trends in the U.S. remain relatively stable. The test positivity rate as of June 7 was at 3%, a slight increase from the previous week. Hospitalizations are currently decreasing, as indicated by the latest data.

The emergence of Nimbus has raised concerns about potential surges in the coming months. Historically, COVID-19 cases have increased during the summer months, prompting experts to caution against possible waves of infection. While the dominant variant currently is LP.8.1, which makes up 38% of cases, the new variant’s rapid growth is noteworthy.

Dr. Albert Ko, a professor of public health at Yale University, expressed that predicting the future impact of Nimbus is challenging but suggested it might not be as severe as previous waves experienced before 2023. Nearly 90% of Americans have been exposed to COVID-19 through infection or vaccination, contributing to a high level of population immunity.

As travel resumes and social gatherings increase, experts urge vigilance. They recommend that high-risk individuals, including those over 65 or with underlying conditions, consider vaccination if they have not received a shot in the last six months. The currently approved vaccines are expected to remain effective against NB.1.8.1.

Though health officials are still gathering data on Nimbus, the variant appears to have a similar symptom profile to prior strains, including cough, sore throat, and fatigue. Public health guidelines remain critical. Individuals are encouraged to practice proper hygiene, consider wearing masks in crowded settings, and stay home if symptomatic.

As the situation develops, health officials are monitoring the variant closely and updating guidelines to ensure public safety during this pivotal time.