He acknowledged that a gap in federal law had made it legally difficult to compel the White House to go beyond captioning, as states have. “But it is a moral imperative,” he said, “especially when every person must know what to do to avoid infecting everyone else.”

President Trump has indicated that he is backing away from the briefings, saying they are no longer worth his time.

Into this whirl has come Ms. Burton, a Chicago-born former teacher of K-12 deaf children who agreed on March 13 to help interpret public health news briefings for Los Angeles County. The local updates, usually right after Gov. Gavin Newsom’s noon briefings, have become must-see viewing as infections have soared in the county to 42,425 cases, with 1,677 deaths. “I didn’t know the scope of what I was getting into,” Ms. Burton says.

A whole new lexicon has come with this pandemic, often requiring on-the-fly interpretation: “bend the curve,” “personal protective equipment” and “social distance” — the term Americans have adopted for keeping clear of friends, neighbors and strangers alike.

Then there is a new phrase that was widely circulated as a precaution after Mr. Trump raised some unorthodox, and potentially dangerous, suggestions about potential virus treatments: “Don’t drink Clorox.”

“I don’t know how I’m going to do that one,” Ms. Burton said, bemused. “I’ll probably have to spell ‘bleach,’ and then for clarity sign ‘use for laundry, makes clothes white, smells bad — don’t drink and don’t put on your body.’”