"I'd go into a room and I didn't remember why I was there," said Diego Ruspini.
"My memory has gotten so much worse, especially short-term memory," said Natalia Ruspini.
California father and daughter Diego and Natalia Ruspini say their entire family was infected with coronavirus in April.
Seventeen-year-old Natalia says simple school tasks, like remembering class times, suddenly became very difficult. "I definitely noticed like my clock in my head was off."
"It's all related, the fact that people are losing their sense of smell, the fact that people are losing their sense of taste, and the brain fog, this whole system is neurological," said Dr. Kari Nadeau, an immunologist and director of the Sean N. Parker Center for Allergy and Asthma Research at Stanford University.
The Ruspinis are in a Stanford study that Dr. Nadeau is conducting on the long-term immunity of COVID-19 patients.
"We know that the virus can affect the astrocytes in the brain," said Dr. Nadeu. "There's probably inflammation too, but not everyone gets it, so we need to understand why this is happening and how to help people."
"It's subtle, but it is very real," said UCSF neurologist Dr. Joanna Hellmuth. "We're actually seeing these changes on cognitive tests that we're giving to people."
Though Dr. Hellmuth says the changes aren't usually visible.
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"In some ways that's not surprising because in other viral diseases that can lead to cognitive changes like HIV or Hepatitis C, sometimes we can see totally normal brain scans," Dr. Hellmuth added.
Both doctors, Hellmuth and Nadeau, say more studies are needed to understand why and how the coronavirus affects cognitive health.
Some initial good news though from Dr. Nadeu: "Once people finish their brain fog, they're back to where they were before."
Six months after her initial COVID-19 infection, Natalia says she's feeling more like herself. "I think time maybe is just the healer."