State Farm had planned to advertise during National Basketball Association games and the N.C.A.A.’s annual men’s basketball tournament. It had also expected to run ads during coverage of the Summer Olympics on Peacock, the streaming service that NBCUniversal is scheduled to start nationwide on July 15. And now?

“We’re trying to deal with all of the cancellations, trying to understand what’s happening here,” Ms. Morris said.

With production studios shut down, and filming of commercials at a standstill, a bare-bones style of advertising has emerged. On a recent night, the NBC late-night host Jimmy Fallon read out a State Farm ad in the manner of a podcaster at the start of his shot-from-home episode of “The Tonight Show.” After plugging the insurance giant, Mr. Fallon held up a scrap of paper on which one of his daughters had scrawled the company’s website address.

On YouTube, the “Tonight Show” episode was preceded in some cases by a State Farm commercial called “New Normal,” a mash-up of old footage and videos made by nonprofessionals.

Many companies are trying to protect their brand names by keeping their ads away from media reports about overrun hospitals, joblessness and death.

As news organizations ramp up their coronavirus coverage, they are losing out on the revenue that would have come their way in more pleasant times, because many companies have stipulated that their ads must not appear near articles that include outbreak-related keywords.

British news organizations, including The Guardian and Daily Mail, wrote in an open letter this week that so-called blacklisting will cost news outlets more than $60 million if the pandemic lasts another three months. “Readers are relying on us right now, and we are relying on advertising,” the publishers noted.