In weather, "nimbus" is a type of cloud associated with heavy precipitation. In health, it's the nickname for a new strain of COVID-19 that recently became the disease's dominant variant in the U.S.

NB.1.8.1, nicknamed "nimbus," is the dominant COVID-19 strain in the U.S. Originating in Europe and Asia in March 2025, it has spread to at least 22 countries. While causing a "razor blade throat" ...