It's been less than a month since health officials reported the first known case of a new and more contagious coronavirus variant in Texas. The man, a Harris County resident, had no travel history.

Four theories could explain the variants' ability to jump from person to person. In recent months, new variants of the virus that causes COVID-19 have been popping up all over the world, and experts ...

The concept can be traced back to a theory from the late 1800s. As evidence mounts that the omicron variant is less deadly than prior COVID-19 strains, one oft-cited explanation is that viruses always ...