The federal government now considers Oklahoma to have "widespread" cases of flu, and it's common even among people who were vaccinated.
Urgent care doctors and all pediatricians are seeing a lot of patients with flu right now. The Center for Disease Control reports flu season arrived earlier and is more severe than usual, in part because the vaccine isn't effective against this year's most common kind of flu.
Eight-year-old Ella has the flu, even though she was vaccinated more than a month ago. The look in her eyes is one doctors are seeing a lot these days.
"Ella has had the flu vaccine, so she doesn't look quite as sick as kids we've seen that have not had the flu vaccine," said Dr. Liz Dunlap, South Tulsa Pediatrics.
Dr Dunlap says in the last week, she's had a wave of sick patients testing positive for flu. Most of her patients, like Ella, were vaccinated, but the strain that's circulating isn't fully covered by the vaccine.
It offers some protection, but Dunlap says it's not complete.
For Ella, it started with a sore throat.
"I just haven't, haven't been getting better every day," Ella said.
Dr. Dunlap says in vaccinated children, the symptoms are the same, just less severe, and slower to appear.
Grownups might dismiss it as a bad cold, thinking they couldn't have the flu if they've had the vaccine.
"Lower grade fevers, the cough is starting more slowly, the body aches and chills and they just don't look quite as sick," she said.
But they're still contagious - which is how Ella might have gotten it, from her sister Lexie, who also had the vaccine.
"I probably got it from a friend at school and gave it my sister but she's a lot worse than me, that's probably because she's younger," her sister Lexis said.
Physicians are running lots of tests these days, and while a few come back negative - most are positive, sometimes for Flu-B, but usually Flu-A; the kind that's causing the most trouble this year.
"We also have just run-of-the mill colds, and strep, but the large majority of the sick child visits right now are the flu," said Dr. Liz Dunlap, South Tulsa Pediatrics.
Because of that basic protection, even though it's not complete, doctors still recommend the vaccine, even now.
It takes about two weeks to be fully effective.