NB.1.8.1 is one of the latest variants of COVID-19, a "slightly upgraded version" of the LP.8.1 variant that is prominent right now, Subhash Verma, microbiology and immunology professor at the University of Nevada, Reno, previously told USA TODAY in May.

The latest COVID variant is causing a distinctive symptom: a sore throat so severe it's nicknamed "razor blade throat." Some patients report a sharp, stabbing pain when they swallow, often at the back of the throat. Because of that, the new variant is informally being called "Nimbus," a name that refers to a jagged type of storm cloud.