npr:

Mild. Moderate. Serious. Severe or extreme.

These are some of the adjectives being used to describe the symptoms displayed by patients with COVID-19. Vice President Pence used them in his remarks to the nation this week:

“Some — some large percentage have mild flu symptoms; some have serious flu symptoms.”

At this stage of the COVID-19 pandemic, there is not a standard definition of what symptoms are associated with these designations.

It can take years for such guidelines to be issued for a newly identified disease, according to Dr. Sandro Galea, an epidemiologist and dean of the Boston University School of Public Health.

Nonetheless, there are some preliminary definitions that can be helpful in understanding the range of symptoms.