May 31, 2022 -- Two-plus years into the COVID-19 pandemic, scientists still aren’t sure how long people who catch coronavirus remain infectious, The Wall Street Journal reports.

Some people keep testing positive with rapid tests beyond five days, and some even test positive after 10 days, the newspaper reported. Are they contagious at the end of their infection period?

“It’s still up for debate,” Nathaniel Hafer, director of operations for the University of Massachusetts Center for Clinical and Translational Science, told the newspaper.

Late last year, the CDC shortened the quarantine and isolation guidelines, saying “people who test positive should isolate for 5 days and, if asymptomatic at that time, they may leave isolation if they can continue to mask for 5 days to minimize the risk of infecting others.”

People who follow those guidelines, however, may be leaving isolation when they’re still contagious, especially if they don’t wait for a negative rapid test, health experts say.

“We know that people will be returning to work while they’re still infectious, even if they feel better,” Carina Marquez, an associate professor and infectious-disease doctor at the University of California, San Francisco, told The Wall Street Journal. Marquez said she tested positive for 13 days while working remotely.

Marquez said people who can’t work remotely have two options: stop isolating after a negative test or stop isolating after 10 days and wear a mask, whichever comes first.

The University of Chicago found that feeling good is not a good reason to end isolation early. Of 260 healthcare workers who felt good enough to return to work 5-10 days after symptoms or diagnosis, more than 40% tested positive, The Wall Street Journal said, citing a preprint study that hasn’t yet been peer-reviewed.

A CDC study found that 54% of people had positive results with a rapid test 5-9 days after symptoms or diagnosis, The Wall Street Journal reported. The percent of positive results decreased over time.

“The high percentage of positive antigen test results during the 5–9 days after symptom onset reinforces the importance of correct and consistent mask use during this period,” the CDC said.

The Wall Street Journal: “Covid-19 Can Leave You Infectious After Five or Even 10 Days”

CDC: “CDC Updates and Shortens Recommended Isolation and Quarantine Period for General Population”

CDC: “Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022”

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