Australia experienced an early start to its flu season, which is beginning to cause a spike in illnesses. According to a recent CNN report, Australia’s rising flu cases may be in indicator of what is coming to the U.S. later this year.

The Australian Department of Health and Aged Care reported a sharp increase in cases in early May, accounting for case numbers higher than the country’s five-year average. Children appear to be getting sick more often than other age groups, and the Atlanta-based Centers for Disease Control and Prevention’s Epidemiology and Prevention Branch influenza division chief Carrie Reed said it’s worth U.S. scientists keeping an eye on.

“We closely monitor what happens in countries throughout the Southern Hemisphere this time of year, just to see what’s happening during their flu season,” she told CNN. “It’s not always a predictor of what’s going to happen here the next season, but yes, we do. We do closely monitor that all summer long.”

The CDC’s formal forecasting effort, a collaboration with academic groups and private industry, has been compiling flu data for roughly 10 years. It’s a process that comes with unique obstacles each year.

“We’ve learned a lot, and we’ve improved a lot over the years,” Reed said. “Flu is a very interesting pathogen to deal with. Every flu season is a little bit different. The virus is constantly evolving. And so every year, it is a new challenge.”

The challenge of predicting the flu ultimately comes down to the human factor.

“It’s a mix of human behavior, social interactions, mobility, but also weather humidity, population immunity,” she said. “So yeah, it’s complex.”

Reed said Australia’s flu numbers are integral to her and her colleagues, but they are not ready to make any 2023 U.S. flu season predictions just yet.

“It’s pretty early so far to predict what the upcoming season might be,” Reed said. “There’s lots of things that could change between now and when we start seeing more flu activity.”