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.

Then, his heart stopped. Doctors were able to resuscitate him. Then, they got to work trying to figure out what was wrong.

Matters of the heart are truly sensitive, especially when its electrical system is disrupted. This is also called an ...