The U.S. could be next, experts say. The country should prepare for a “pretty bad flu season” with COVID cases intermingled, top U.S. infectious disease expert and presidential physician Dr. Anthony Fauci recently told Bloomberg.

His prediction, shared by other experts, is based on cases in Australia this past summer (its winter). Scientists in the Northern Hemisphere watch the Southern Hemisphere for signs of what the flu season might be like. This year, Australia’s flu season was shorter than normal, but cases peaked earlier and much higher, and children and teens bore the brunt.

“If you look at what happened in the flu season in the Southern Hemisphere, Australia got whacked pretty badly,” Dr. Georges Benjamin, executive director of the American Public Health Association, told Fortune. “I anticipate a bad flu season at the very least,” if not a bad COVID season as well.

The first flu season after the start of the pandemic was practically nonexistent, likely thanks to COVID-19 precautions like masks, social distancing, and quarantining that also prevented the spread of the flu. Scientists then predicted that last year’s flu season would be a doozy—a  “twindemic” of sorts, due to its overlap with COVID. 

And yet it wasn’t, according to a recent article in the Journal of the American Medical Association. While the U.S. flu season was worse than the season prior, it was mild compared to previous pre-pandemic flu seasons.

This year, however, COVID precautions are virtually nonexistent—and the U.S. could be poised for the long-awaited phenomenon, Dr. William Schaffner, an infectious disease professor at Vanderbilt University, recently told NPR.

“This could very well be the year in which we see a twindemic,” he said. “That is, we have a surge in COVID and simultaneously an increase in influenza. We could have them both affecting our population at the same time.”

Flu cases began ticking up in the U.S. last month, with nearly 700 cases reported the second-to-last week of September, and the percent of positive flu tests rising over the past month.

Last week officials from the White House and Centers for Disease Control met with health system and hospital leaders due to concerns regarding a potential surge of both COVID and flu later this year. Federal health officials are encouraging Americans to receive their flu shot and new Omicron-specific vaccine booster at the same time this fall, saying doing so is both safe and convenient.

Benjamin also recommends stocking up on COVID tests.

“If you get flu-like symptoms, check for COVID,” he said. “And if it’s not COVID, go to the clinic and see if it’s flu. It’s probably going to be one or the other.”