COVID Nimbus Variant Fuels Rising ER Visits in 27 States as Summer Wave Builds Across the U.S.

A COVID-19 subvariant that drove surges in China and Southeast Asia earlier this year has now become the dominant strain in the United States and is fueling rising emergency department visits across 27 states, according to the latest federal surveillance data. The variant, known as NB.1.8.1 and informally called "Nimbus," accounts for an estimated 43% of all sequenced U.S. COVID cases as of late June 2026, according to CDC genomic surveillance data. Wastewater levels classified as "high" or "very high" have been confirmed in Alabama, Alaska, California, Florida, Hawaii, Kentucky, Louisiana, and Texas, and public health officials are urging high-risk individuals to verify their vaccination status before summer travel reaches its peak.

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