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Carl Bergstrom in The Washington Post on understanding coronavirus test results

Tuesday, July 21, 2020 - 13:45 to Wednesday, October 21, 2020 - 13:45

Americans are being swabbed by the thousands to learn if they have covid-19, the disease caused by the novel coronavirus. It’s how many are determining their risk of contracting or spreading the virus to someone else.

Experts say testing is a vital component to controlling the outbreak, but one test result still isn’t a green light to visit vulnerable friends or family members. The nature of covid-19, the time it takes for someone to develop symptoms and the varied ways the virus affects people make each test a snapshot in time more than a definitive answer.

“I personally wouldn’t consider a single test a license to go see my parents, who are older and would be at higher risk,” said Carl Bergstrom, a University of Washington biology professor who studies infectious diseases.

The viral swab tests, seen at drive-through clinics across the country, tell people whether they’re infected with the novel coronavirus on that particular day, said Lucy Wilson, an infectious-disease specialist and a professor at the University of Maryland Baltimore County.

It takes time for the coronavirus to replicate to a critical mass for a swabbing test to detect it. The time this process takes varies from person to person and ranges from two to 14 days, experts say.

“The problem is this virus is a strange virus,” Bergstrom said. “The timing varies a lot in people.”

Imagine that you become infected today and are tested tomorrow; Bergstrom said “we have every reason to believe you’re going to test negative, even though you’re infected.”

Read the whole article in The Washington Post.

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