(CNN) Shelby Hedgecock thought a negative Covid-19 test meant she had recovered from her initial infection. But three months and another positive test later, she told CNN she is still feeling unwell.
"I'm having neurological issues, cognitive issues, trouble putting words together," she told CNN's Chris Cuomo on Wednesday. "It's just all over the place, and I am insanely tired."
As health experts work to get the virus under control, stories like Hedgecock's raise concerns about whether people can get reinfected and if herd immunity is possible.
Hedgecock first tested positive for coronavirus on April 20. On May 9, she tested negative, she said.
Nearly two weeks later, she took an oral and nasal swab test. The oral test came back negative, but the nasal came back positive.
A week later, another test was negative, she said.
And still she feels symptoms, she said. Any exertion can put her in bed for days, and she is now on medication for daily headaches, she said.
It's not clear that the second positive test means Hedgecock was infected again. It's possible she initially received false negative test result or that the positive was misleading, CNN's chief medical correspondent Sanjay Gupta said.
"We are not getting documented cases of reinfections yet ... That's not to say they won't come," Gupta said. "If people were losing their immunity I think now, six months into this, we would be seeing significant amounts of reinfection."
Some types of coronavirus tests have a 15 to 20% false negative rate, he told Cuomo Wednesday.
"If that's the case, then people have been walking around with a false sense of security for a long time," Hedgecock said. "And that's a problem."
Testing positive after an infection could come from the test looking for genetic material of the virus, Gupta said. The genetic material identified could be a sign that the virus is present, or it could be debris the virus left behind, he said.
"We are all learning," Gupta said.
Recent studies have investigated immunity after coronavirus infection.
"These (studies) are very significant for the future of this epidemic," Dr. William Haseltine, a former professor at Harvard Medical School and Harvard School of Public Health, told Erin Burnett Monday on OutFront.
Haseltine said a recent study that found peoplewho have been infected with the new coronavirus could see their immunity decline within months is just "what we were afraid of."
If the findings turn out to be true, Haseltine said, they could have implications for infected individuals, for the idea of achieving herd immunity against the virus, and for the development of a vaccine.