COVID-19 cases are climbing again in the United States this summer, fueled by two fast-spreading variants known as NB.1.8.1 (nicknamed “Nimbus”) and XFG (“Stratus”). The Centers for Disease Control and Prevention (CDC) reports rising infections in 40 states, particularly across the Mid-Atlantic, Southeast, South, and West Coast. Nine states remain stable, but none are seeing declines. While case numbers are still far lower than during past surges, emergency room visits for COVID-like symptoms are up.
Nimbus has become the dominant strain nationwide, known for causing an intense sore throat often described as feeling like “razor blades.” Stratus is now the third most common variant and is spreading quickly. Experts from Yale University note that both variants transmit more easily than earlier strains and can partially evade immunity from prior infections or vaccinations.
States such as Alabama, Alaska, California, Delaware, Florida, Hawaii, Kentucky, Louisiana, and Texas are experiencing high or very high virus levels. Other states — including New York, New Jersey, Pennsylvania, Washington, and Georgia — are also seeing a steady climb in cases.
Health experts attribute the summer spike to increased travel and people spending more time indoors in air-conditioned spaces to escape the heat. Dr. William Schaffner of Vanderbilt University says COVID tends to have two waves each year: a smaller summer rise and a larger winter surge.
Symptoms from Nimbus and Stratus remain similar to recent Omicron variants: sore throat, fever, cough, congestion, headache, muscle aches, fatigue, loss of taste or smell, nausea, and diarrhea. Children under four — many of whom remain unvaccinated — currently account for the highest rate of emergency room visits.
Although hospitalizations remain lower than in previous peaks, the World Health Organization warns that the virus continues to evolve and could produce more contagious or severe forms. The U.S. Food and Drug Administration also stresses that COVID-19 can still lead to serious illness and death, even in smaller waves.
The CDC recommends staying up to date with COVID-19 vaccines and boosters, particularly for older adults, people with underlying conditions, and frontline workers. Updated boosters are designed to better target variants like Nimbus and Stratus, offering improved protection. Other preventive measures include testing after exposure, wearing high-quality masks in crowded indoor spaces, and isolating when sick.
Experts believe the summer wave could continue for several months before easing in the fall, with a larger surge expected in the winter.