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UW-Eau Claire senior Megan Hutera of Rice Lake swabbed her nose for an antigen test on campus with the help from RN Shelby O’Rourke on Tuesday. Hutera tested negative for COVID-19. While experts say getting tested for COVID-19 before attending Thanksgiving gatherings is better than not, state and local experts warned this week that a negative test result won’t necessarily be accurate if it’s done too soon after someone’s exposure to the virus. View more photos at LeaderTelegramPhotos.com.

EAU CLAIRE — Just because you test negative for COVID-19 doesn’t mean it’s safe to travel to another household for a large Thanksgiving gathering, local and Wisconsin experts say.

A COVID test won’t be accurate if the person is swabbed too soon after they were exposed, experts and studies say.

“A negative test is just a snapshot in time,” said Andrea Palm, Wisconsin Department of Health Services secretary-designee, in a call with reporters Tuesday. “ … However, considering incubation time for COVID-19, the virus may become detectable at a later time ... a negative test is not a free pass.”

The novel coronavirus can incubate for between two and 14 days before a person starts having symptoms. Some studies suggest that people are most infectious before they even show symptoms.

It can take up to 14 days before someone shows symptoms after being exposed to the virus, but the most common time frame for symptoms is four to five days after exposure, the Centers for Disease Control and Prevention said.

The Massachusetts-based MIT Medical clinic set the average at five to six days between exposure and symptoms. That’s about the same time frame after exposure for a PCR test to be able to detect the virus in the body, MIT Medical wrote on its website in October.

But an April study suggested that about 44% of COVID-19 infections that were studied spread from person to person before symptoms even showed — suggesting that a person could be infectious before they show symptoms, according to MIT Medical.

The World Health Organization also noted in April that people who are “pre-symptomatic” with COVID-19 can transmit the virus to others.

A negative test within six or fewer days after exposure is a “very, very poor indicator” of whether or not a person actually has COVID-19, Dr. Alan Wells of the University of Pittsburgh Medical Center told The Associated Press last month.

“You can test negative on a pregnancy test, and it might just be too early,” said Lieske Giese, director of the Eau Claire City-County Health Department. “A few days later you might test positive. It’s the same principle. The test is detecting those viral particles, and it may be that it’s a bit too early to check for that. Tomorrow or the next day you may test positive.”

But if people absolutely have to travel for the holiday or be close to people in a high-risk demographic, it’s a good idea to get a test anyway, health officials have said.

The elderly and people with pre-existing medical conditions are more likely to be hospitalized or die of the virus than others, data indicates.

A negative COVID-19 test result is better if people also quarantine for two weeks before and after they travel, Giese said at a press briefing last week.

“It’s not a bad (idea) to test, but it’s not sufficient as a green light,” Giese said Tuesday. “Once you leave the testing location, any exposure you had from that point forward also puts you at risk and can make you infectious when you land at the Thanksgiving dinner table.”

Wisconsin and nationwide health officials have repeatedly pleaded with the public to stay at home for the holiday.

“If you’re planning to celebrate Thanksgiving outside your household, we strongly urge you to reconsider,” Wisconsin Gov. Tony Evers said Tuesday in a call with reporters.

The virus is still spreading at critically high levels in Wisconsin, although new cases are finally beginning to dip after a record high in mid-November. Another 6,200 people tested positive for COVID-19 Tuesday, and 104 people died — a new single-day record for virus-related deaths in the state.

Contact: 715-833-9206, sarah.seifert@ecpc.com, @sarahaseifert on Twitter

Sarah Seifert is the L-T's education and health reporter. She has worked as a journalist in the Chippewa Valley since 2017 and joined the L-T in 2019. Get in touch at sarah.seifert@ecpc.com or on Twitter @sarahaseifert.