UAB infectious disease expert explains CDC’s COVID isolation guidance

Published: Jan. 5, 2022 at 5:54 PM CST
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BIRMINGHAM, Ala. (WBRC) - Many are still scratching their heads about the Centers for Disease Control’s guidance about the COVID-19 isolation period.

The CDC recently changed the guidance to say some COVID-positive people can come out of isolation after five days, as long as they wear a mask.

Local doctors said the guidance really isn’t all that confusing if you look at the science and consider the length of time you’re actually shedding the virus.

The CDC now says it’s okay to come out of isolation after five days following a positive COVID test.

Prior to the new guidance, the isolation period was 10 days.

Many have attacked the agency’s new guidance, but UAB infectious disease expert, Dr. Michael Saag, said the key is understanding the virus’s transmissibility.

“The peak time of transmission occurs about…starts at about 12 hours before someone develops symptoms and then peaks out at about a day and it’s pretty much drifting away by day three to five. That means after day five, it’s very uncommon for transmissible virus to be out there from someone who’s infected,” Dr. Saag explained.

He said the virus is most contagious in the first few days, which is why the CDC changed its guidance.

But if COVID stops being transmissible after around five days, why is the CDC still requiring masks for an additional five days?

“It can drag out to day seven or eight in low levels, so that’s why just to be extra sure out to day 10 is recommended just to be extra sure that there’s no transmission,” Dr. Saag said.

Many have also criticized the CDC for not requiring people to test for COVID negative before returning to normal activities.

Dr. Saag said testing out of isolation is a bad idea.

“We know that that transmissible virus is almost impossible to detect after the day seven, let’s say, but yet, PCR tests, and even antigen tests, can remain positive for day 10, day 12, day 15, sometime for PCR, a month or two after the infection has cleared. So, testing may give you a longer time in isolation when it’s not necessary,” Dr. Saag explained.

Dr. Saag said to think of it like this: Day zero is the day you start having symptoms.

If all of your symptoms are gone by day five, you can come out of isolation wearing a mask for an additional five days.

But if you still have symptoms at day five, you should remain in isolation until all your symptoms subside.


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