Norovirus causes an average of 900 deaths annually mostly among older adults, 109,000 hospitalizations, and 19 million to 21 million cases in the U.S. each year.

PANDAS syndrome is the result of an autoimmune response to a strep infection. Learn about causes, symptoms, treatment, and more at WebMD.

Treatment options Viral infections often have to run their course. Unlike bacterial infections, they don’t respond to antibiotics, so treatment usually focuses on relieving symptoms.

A contagious new COVID-19 variant called NB.1.8.1, aka "Nimbus," is now dominant in the United States, CDC data show. What to know about symptoms and vaccines.