Flu activity is picking up across the country, indicating an earlier start to this year's flu season, particularly in the South and in the West, according to the Centers for Disease Control and Prevention.

The uptick doesn't necessarily mean it's going to be a bad season — flu is notoriously unpredictable — but some clues from earlier this year point to a potentially harsh season. The flu season in Australia, which can be a sign of what's to come in the Northern Hemisphere, arrived early and with a vengeance.

Friday, the CDC reported widespread flu in five states: Alabama, California, Louisiana, Nevada and South Carolina. This time last year, no states showed widespread activity.

In addition, high levels of flu were reported in seven states — Alabama, Arkansas, Georgia, Mississippi, Nevada, South Carolina and Texas — plus Puerto Rico. Last year, only one state reported high levels of flu at this time.

Nationally, flu activity was above the national baseline for the first time this season. Flu activity is measured by looking at the percentage of visits to the doctor's office for flu-like illnesses. This week, 2.5 percent of visits were for flu-like illnesses, surpassing the baseline of 2.4 percent.

Four children have died so far this season from flu-like illnesses, the CDC reports.

Though flu activity is picking up, it's not too late to get a flu shot. "The flu season is just getting started," the CDC says. The flu vaccine "is always the best way to prevent flu and its potentially serious complications."

The standard flu shot this year includes protection against several strains of influenza, including H1N1, H3N2, and B/Victoria viruses.

The CDC reported that, so far this year, Victoria viruses are the most common strains of flu detected, followed by strains of H1N1 and H3N2. The Victoria strain has been more common in children and young adults, and the H1N1 strain more common in adults ages 65 and up.

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