CDC reverses controversial coronavirus guidance that said people without symptoms may not need a test

The Centers for Disease Control and Prevention on Friday reversed controversial coronavirus testing guidance that said people who were exposed to an infected person but weren't showing any symptoms did "not necessarily need a test."

The new guidance says that people without symptoms who have been in close contact with an infected person "need a test."

"Please consult with your healthcare provider or public health official. Testing is recommended for all close contacts of persons with SARS-CoV-2 infection," the new guidance says. "Because of the potential for asymptomatic and pre-symptomatic transmission, it is important that contacts of individuals with SARS-CoV-2 infection be quickly identified and tested."

Numerous studies have shown that people can carry and spread the virus without showing symptoms — both in the presymptomatic stage and in cases where there never never develop symptoms. Public health specialists and officials at the World Health Organization have repeatedly emphasized the importance of testing people who don't have symptoms in order to cut off chains off transmission. 

Many public health specialists criticized the CDC's change in testing guidance in August for appearing to downplay the significance of testing people who don't have symptoms but who might be spreading the virus. 

The CDC called the change in guidance a "clarification" and noted the "the need to test asymptomatic persons."

Representatives from the Department of Health and Human Services, which the CDC falls under, did not immediately return CNBC's request for comment. 

CDC Director Dr. Robert Redfield told lawmakers earlier this week that the agency was planning on updating the guidance this week. 

"Pending test results, you should self-quarantine/isolate at home and stay separated from household members to the extent possible and use a separate bedroom and bathroom, if available," the new guidance says.

The updated guidance also says that people who don't have symptoms and who have not been exposed to an infected person "do not need a test unless recommended or required by your healthcare provider or public health official." The previous guidance definitively said that such people do not need to be tested.

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