Public health experts trying to predict the severity of the upcoming flu season in the U.S. often look to the Southern Hemisphere for clues. Here’s the word from Down Under, where winter recently ended:

Brace yourself, America.

Australia, which saw an earlier-than-usual peak of flu cases, had a rough season. The country was hit hard with a particularly virulent flu strain, H3N2, which generally causes more severe illness, especially in seniors.

U.S. health officials are urging people to get their flu shot as soon as possible, and certainly by the end of the month.

Australia's Department of Health recently said 662 people have died from the flu this season, and more than 270,000 people have gotten sick, making it one of the worst outbreaks in the country's history.

"When data started coming out from Australia, it got everyone's attention," said Dr. William Linam, a pediatric infectious disease specialist at Children's Healthcare of Atlanta. "It put us on notice to start making sure we're ready, maybe even a little earlier than we already are."

Linam and other experts stressed the Australian flu season doesn’t always predict the U.S. one.

So far, weekly surveillance data shows minimal flu activity in Georgia, according to the state Department of Public Health. But, as weather cools, flu activity will start to pick up. The season usually ramps up in October and peaks between December and February. But the season can also extend into May — like it did this past season.

It takes about two weeks after a flu shot for antibodies to develop in the body, according to the Centers for Disease Control and Prevention.

MORE: UGA gets major funding to develop flu vaccine

Logan Edwards, 7, of Conyers, receives an flu vaccine shot from Katie Childress, a licensed practical nurse, during a visit to Conyers Pediatrics in Conyers, Wednesday. (Alyssa Pointer/Atlanta Journal Constitution)

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Dr. Hugo Scornik, a Conyers pediatrician, said that, while the severe flu season in the Southern Hemisphere is concerning, no one can easily predict the severity of the season here, or exactly what strains will be circulating. "The only thing predictable about the flu is that it's unpredictable," he said, repeating an often-quoted axiom.

Even within the U.S., there can be regional differences.

At the start of the year, many states saw a late flu season surge of H3N2 activity. But in Georgia, that strain was more prevalent at the beginning of the season.

Georgia’s 2017-18 flu season was particularly brutal. The long-lasting flu season didn’t subside until the end of April. It claimed 145 lives statewide and led to more than 3,000 hospitalizations in metro Atlanta. Six months earlier in Australia, an intense flu outbreak foreshadowed the deadly outbreak here.

The flu causes fever, headache, muscle pain and can lead to complications such as pneumonia, which can be serious and even deadly.

The flu vaccine is available at Conyers Pediatrics in Conyers. (Alyssa Pointer/Atlanta Journal Constitution)

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Each year, 5% to 20% of the U.S. population gets the flu; tens of thousands are hospitalized; and thousands die from a flu-related illness.

Flu vaccine effectiveness can vary, but it’s generally ranged between 40% and 60% over the past several years. Effectiveness was only 19% during the 2014-15 year.

While many companies and schools offer free flu shots, polls show more than a third of Americans decline.

Experts stress that, even if you come down with the flu, the vaccine can still offer protection. It lessens the severity of the flu and reduces the chance of experiencing complications. Getting a vaccine also can shorten the length of the illness if you do get sick.

Seniors, young children and people with chronic health conditions are at most risk for serious, flu-related complications, but the flu also kills healthy people every year.

Scornik pointed to a new hashtag, promoted by the American Academy of Pediatrics, as a catchy way to remember to get a flu shot before the end of the month — #FluBeforeBoo.

He, his wife and two sons got their flu shots two weeks ago.

An Influenza Vaccine poster is displayed at Conyers Pediatrics in Conyers. (Alyssa Pointer/Atlanta Journal Constitution)

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More details

Each year, 5% to 20% of the U.S. population gets the flu. Tens of thousands are hospitalized.

During the 2018-19 flu season, more than 1,500 in metro Atlanta were hospitalized for flu-related illnesses, and 44 people in Georgia died from the flu.

Georgia’s 2017-18 flu season was particularly brutal. It claimed 145 lives statewide and led to more than 3,000 hospitalizations in metro Atlanta.

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