The list of close contacts of President Donald Trump who have tested negative for COVID-19 continues to grow, but experts say it doesn’t mean they are off the hook: A single negative test doesn’t mean a person doesn’t have the virus.

“A negative is not a Get Out of Jail Free card,” Dr. Alan Wells, medical director of clinical laboratories at the University of Pittsburgh Medical Center.

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COVID-19 diagnostic tests look for bits of the coronavirus in a person’s body at that exact moment. But “it takes a number of days for the virus to replicate enough to be detected,” Wells told NBC News.

That’s why the Centers for Disease Control and Prevention advises anyone who may have been exposed to quarantine for 14 days, which is believed to be the extent of the incubation period.

Vice President Mike Pence and his wife, Karen,