File photo: CGTN

The U.S. Centers for Disease Control and Prevention (CDC) on Friday updated again on its website the guidelines for testing people who do not have symptoms of novel coronavirus.

"Due to the significance of asymptomatic and pre-symptomatic transmission, this guidance further reinforces the need to test asymptomatic persons, including close contacts of a person with documented SARS-CoV-2 infection," according to the website.

"Testing is recommended for all close contacts of persons with SARS-CoV-2 infection. 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," the CDC explained.

It is a change from the CDC guidance released last month which said testing might not be necessary for people without COVID-19 symptoms.

"Viral tests are recommended to diagnose acute infection of both symptomatic and asymptomatic individuals, to guide contact tracing, treatment options, and isolation requirements," according to the CDC website.

The guidance notes that even if people do not have symptoms, they still need a test if they have been in close contact - such as within 6 feet - of a person with coronavirus infection for at least 15 minutes.

"In areas where there are a small number of new cases and limited spread, your public health department may request a small number of asymptomatic 'healthy people' to be tested," said the updated guidance.

If there is significant spread of the virus in the community, public health department may request significant numbers of asymptomatic "healthy people" to be tested in order to help stop the spread of the virus, according to the guidance.

On August 24, the CDC changed COVID-19 testing guidelines on its website, no longer recommending testing for most people without symptoms.

The move has sparked controversy as experts warn it may hamper the timely identification of asymptomatic individuals with COVID-19.

According to a report of The New York Times earlier this week, the recommendation published in August was not written by CDC scientists and was posted to the agency's website despite their serious objections.