Dr. Hana El Sahly is an associate professor of molecular virology at Baylor College of Medicine.
She spoke with Eyewitness News on Monday as Houstonians rush to get testing ahead of the holiday.
"A negative test is not enough to give us reassurance that we're not incubating the virus," said Sahly. "We know this incubation period is anywhere between two and 14 days, so if they test today and fly tomorrow to the family gathering, it's very plausible that within four or five days they will come with an infection despite a negative test prior to travel. That's the tricky part of the virus."
Shaly recommends people avoid traveling for Thanksgiving. The CDC issued the recommendation last week.
In Arlington, a family's brush with the virus is being used as a warning to others who might be considering big get-togethers this holiday.
Alexa Aragonez said her family weighed the risks of catching the virus but decided to get together for a birthday party on Nov. 1.
A couple of days after the party, her 57-year-old mother, Enriqueta Aragonez, and others who were at the party began to feel sick. They got tested, and all 12 who had attended were positive for COVID-19. Three other people with whom they had come in contact with also tested positive, said Alexa Aragonez, 26, who didn't attend the party.
READ MORE: 15 Texas relatives sick with COVID-19 after party 'feel guilty'
Follow Steve Campion on Facebook, Twitter and Instagram.