NEW YORK (AP) — February is usually the peak of flu season, but not this year. Health officials say flu cases and hospitalizations have been at their lowest levels in decades.

Nationally, “this is the lowest flu season we’ve had on record,” according to a surveillance system that is about 25 years old, said Lynnette Brammer of the U.S. Centers for Disease Control and Prevention.

Experts say that measures put in place to fend off the coronavirus — mask wearing, social distancing and virtual schooling — were a big factor in preventing a “twindemic” of flu and COVID-19. A push to get more people vaccinated against flu probably helped, too, as did fewer people traveling, they say.

Some think it's also possible that the coronavirus has essentially muscled aside not only flu, but also some other bugs usually seen in the fall and winter.

More than 190 million flu vaccine doses were distributed this season, but the number of infections is so low that it’s difficult for CDC to do its annual calculation of how well the vaccine is working, Brammer said. There’s simply not enough data, she said.

That also is challenging the planning of next season’s flu vaccine. Such work usually starts with checking which flu strains are circulating around the world and predicting which of them will likely predominate in the year ahead.

“But there’s not a lot of (flu) viruses to look at,” Brammer said.