The U.S. is starting to see signs of an early flu season this year. According to tracking by the Centers for Disease Control and Prevention, visits to doctors' offices for respiratory illness are already above baseline levels, and more people are testing positive for influenza.

(NEXSTAR) – The U.S. is starting to see signs of an early flu season this year. According to tracking by the Centers for Disease Control and Prevention, visits to doctors' offices for respiratory illness are already above baseline levels, and more people are testing positive for influenza, especially in the south and southeast.

The CDC tracks influenza activity on a map showing all U.S. states and territories. The map, which uses data through Oct. 15, shows only one place — Washington, D.C. — with flu activity categorized as "very high."

Five states, shown on the map in red, have a "high" level of flu activity: Texas, New York, Tennessee, Georgia and South Carolina.

Louisiana, Alabama and Puerto Rico are also categorized as "high," but have lower numbers and therefore are shaded in orange.

Some local jurisdictions also report data to the CDC. Of those with data available, the metro areas of San Antonio, Texas; Memphis, Tennessee; Champaign-Urbana, Illinois; and Columbus, Georgia, had "very high" levels.

The map isn't based off confirmed influenza lab tests, but rather tracks where people are going to the doctor with flu-like symptoms (respiratory illness and fever, plus a cough or sore throat). Because of that, the map "may capture patient visits due to other respiratory pathogens that cause similar symptoms," the CDC explains.

Flu season is ramping up at the same time as children's hospitals are reeling from an onslaught of young patients with Respiratory Syncytial Virus, or RSV. CDC tracking shows RSV cases spiking over the past month.

On top of that, there's always the threat of another COVID-19 surge as we head into the colder months, and people move outdoor socializing indoors, where the virus spreads more quickly.

"This virus actually knows how to get us. It follows humans, meaning that we are going to be together, we're going to be in those spaces with poor ventilation, and COVID-19 loves that," said Dr. Ilan Shapiro, chief medical affairs officer at AltaMed in Los Angeles. Influenza and RSV also spread quickly under the same conditions, Shapiro said.

All three viruses also have overlapping symptoms. If you feel sick and aren't sure which virus you have — COVID, influenza or RSV — Shapiro recommends getting tested, as each virus has different treatment options.