February is usually the peak of flu season in the global north, with doctors’ offices and hospitals packed with suffering patients. But not this year.

In the US, doctors are reporting that flu has virtually disappeared, with fewer infections than anything seen in decades, reports the Associated Press.

“This is the lowest flu season on record,” said Lynnette Brammer of the US Centers for Disease Control and Prevention. Hospitals say the expected steady stream of flu-stricken patients never materialised.

Experts say that measures put in place to fend off the coronavirus – mask wearing, social distancing and virtual schooling – have been a big factor in preventing a “twindemic” of flu and Covid-19.

Another possible explanation is that the coronavirus has essentially muscled aside flu and other bugs that are more common in autumn and winter.

Scientists don’t fully understand the mechanism behind that, but it would be consistent with patterns seen when certain flu strains predominate over others, said Dr Arnold Monto, a flu expert at the University of Michigan.

“I have seen zero documented flu cases this winter,” said Dr Nate Mick, the head of Maine Medical Center in Portland, Oregon.

The numbers are astonishing considering flu has long been the nation’s biggest infectious disease threat. In recent years, it has been blamed for 600,000 to 800,000 annual hospitalisations and 50,000 to 60,000 deaths.

Some doctors say they have even stopped sending specimens for testing this winter, because they don’t think flu is present. Nevertheless, many labs are using a CDC-developed “multiplex test” that checks specimens for both the coronavirus and flu.

More than 190 million flu vaccine doses were distributed in the US 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.

Across the globe, flu activity has been at very low levels in China, Europe and elsewhere in the Northern Hemisphere winter.

That follows reports of little flu in South Africa, Australia and other countries during the Southern Hemisphere’s winter months of May through August.