An ICU nurse in Texas has found herself in the position of some of the very same patients she’s spent the last few weeks treating — hospitalized with Covid-19 even after testing negative for the virus.

Heather Valentine, 24, isn’t exactly sure whom she may have picked it up from and told CNN on Tuesday that she was reluctant to even accept that she had symptoms.

Valentine was exhausted a week ago after her third daily hospital shift in a row in Houston, she said, but didn’t think much of it until the body aches, a fever and a small cough surfaced.

On Wednesday, Valentine said she took a rapid antibody test, which came back negative. Antibody tests can help identify recent past infections, not current ones, though even when antibodies are present, the tests can be wrong up to half the time, the US Centers for Disease Control noted in May.

The next day, she took a viral test that also came back negative. Issues with samples, testing or timing of tests can all lead to false negatives. It’s not clear whether she was tested again.

On Saturday, her doctor, Joseph Varon, called and asked Valentine to go in for a CT scan, she said. Between the CT scan results indicating the virus’ effect on her lungs and other lab results, Valentine said Varon told her he was certain she had Covid-19, even though her swab test had come back negative.

“I could’ve required intubation if I would have waited a couple days more,” Valentine said, “which is so crazy to hear as an ICU nurse.”

Texas reported 10,351 new cases Saturday, topping the previous record of 10,028 set July 7, according to the Department of State Health Services. With a surge in new cases, hospitalization rates across the US are simultaneously increasing, causing some emergency room doctors to worry about the immediate future.

Regardless of how young or how healthy someone thinks they are, Valentine said it’s important to still be careful.

As a frontline worker, it’s been hard, Valentine said. She and her colleagues are getting tired, but they’re making every effort to make sure patients are taken care of.

The way to fight the coronavirus, Valentine said, is to respect one another and to understand that even though someone doesn’t have symptoms, there’s still no guarantee they may not have it.

“If you have any kind of symptom, stay home, get checked out, don’t wait until you can’t breathe to go get help,” she said.

Valentine is still in the hospital but said she’s doing much better than the day she was admitted.

“You never think it’s going to happen to you, but I’m a perfect example,” she said. “Take every precaution, wear a mask, don’t go out if you don’t have to, it’s not worth it.”