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How long is someone with COVID-19 contagious?

Medical experts say virus is transmittable for 10 days

UHS expert explains how the 10-day window was established for how long COVID-19 patients are contagious.
UHS expert explains how the 10-day window was established for how long COVID-19 patients are contagious.

SAN ANTONIO – Once diagnosed with COVID-19, how long should someone isolate before safely resuming with their normal activities?

Dr. Jason Bowling, a hospital epidemiologist with University Health System, said an isolation period of 10 days is required before the novel coronavirus dies off.

For symptomatic people, that means isolating since the onset of symptoms, like shortness of breath, dry cough and a fever. They should also continue monitoring their own symptoms until they improve, Bowling said.

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For asymptomatic people who don’t know when they were exposed, that means the isolation period starts after receiving a positive lab test.

Isolation is not to be confused with quarantining. People exposed to the virus are recommended to quarantine for 14 days, which is the incubation period of the virus.

Recently, the Centers for Disease Control updated its recommendations, indicating that asymptomatic patients should be considered as recovered after 10 days.

Bowling said the 10-day window was determined after researchers grew viral cultures of the virus to see how long it stays alive.

“In people that have mild to moderate disease, so generally people that haven’t been in the hospital, those cultures don’t grow past eight or nine days,” Bowling said. “So it gives you a little more comfort that that 10-day window is probably pretty accurate for most people that have COVID-19 disease.”

However, people can still test positive for the virus beyond that window, Bowling said.

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PCR tests, considered to be the gold standard in detecting the novel coronavirus, can detect fragments of the dead virus for weeks and even months after the initial positive lab test, Bowling said.

“Now what’s helpful in those research studies that are done in viral cultures is they show that the virus is no longer growing, so they no longer have transmissible virus,” Bowling said.


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