NEW YORK — The U.S. flu season is underway, with at least seven states reporting high levels of illnesses and cases rising in other parts of the country, health officials say.

The Centers for Disease Control and Prevention posted new flu data on Friday, showing very high activity last week in Louisiana, and high activity in Alabama, Florida, Georgia, Mississippi, New Mexico and South Carolina. It was also high in the District of Columbia and Puerto Rico, the U.S. territory where health officials declared an influenza epidemic earlier this month.

Early Start to the Flu Season

“We’re off to the races,” said Dr. William Schaffner, a Vanderbilt University infectious diseases expert

Traditionally, the winter flu season ramps up in December or January. But it took off in October last year, and is making a November entrance this year.

Flu activity was moderate but rising in New York City, Arkansas, California, Maryland, New Jersey, North Carolina, Tennessee and Texas. And while flu activity has been high in Alaska for weeks, the state did not report data last week, so it wasn’t part of the latest count.

Challenges in Tracking the Flu

Tracking during flu season relies in part on reports of people with flu-like symptoms who go to doctor’s offices or hospitals; many people with the flu are not tested, so their infections aren’t lab-confirmed. COVID-19 and other respiratory viruses can sometimes muddy the picture.

Alicia Budd, who leads the CDC’s flu surveillance team, said several indicators are showing “continued increases” in flu.

Current Flu Strains and Vaccination Rates

There are different kinds of flu viruses, and the version that’s been spreading the most so far this year usually leads to a lesser amount of hospitalizations and deaths in the elderly — the group on whom flu tends to take the largest toll.

So far this fall, the CDC estimates at least 780,000 flu illnesses, at least 8,000 hospitalizations and at least 490 flu-related deaths — including at least one child.

Budd said that it’s not yet clear exactly how effective the current flu vaccines are, but the shots are well-matched to the flu strains that are showing up. In the U.S., about 35% of U.S. adults and 33% of children have been vaccinated against flu, current CDC data indicates. That’s down compared to last year in both categories.

Flu vaccination rates are better than rates for the other two main respiratory viruses — COVID-19 and RSV. About 14% of adults and 5% of children have gotten the currently recommended COVID-19 shot, and about 13.5% of adults 60 and older have gotten one of the RSV shots that became available earlier this year.