During an outbreak like COVID-19, handwashing should be done often – potentially multiple times an hour if you’re interacting with many people or any time you’ve coughed, sneezed, or touched your face.
In general, though, follow the CDC’s guidelines for handwashing:
While preparing food or eating
After using the bathroom
After treating someone medically (specifically for a cut/wound, vomiting, and/or diarrhea)
After coming into contact with animals
After handling garbage