A research team at Seoul National University Boramae Hospital has discovered that the amount of Covid-19 virus detected in adolescent patients' stool was larger than that detected from nose and saliva for a more extended period.

The team, led by Professor Han Mi-sun at the hospital, came to such a conclusion after conducting a study on 12 Covid-19 adolescent patients - nine with mild symptoms and three with no symptoms – under the age of 18 admitted to Boramae Hospital.

As a result, the team found that 92 percent of the stool tested positive for the virus, compared to 73 percent in saliva and nose.

The researchers also analyzed the amount of virus detected from the nose, saliva and stool, by time.

In the case of stool, the initial amount of virus was the highest in both mild and asymptomatic patients and was consistently high after two to three weeks. However, the amount of virus in the nose and saliva tests decreased with time.

The virus in saliva also disappeared faster than the virus in the nose as the team confirmed that 80 percent of the samples taken from saliva tested positive in the first week, but decreased sharply to 33 percent in the second week and 11 percent in the third week.

The researchers, however, stopped short of confirming whether the virus detected in the stool was infectious.

“Since the virus is not cultured, the infectivity is unknown,” the team said. “However, given previous findings that infectivity is related to the amount of virus and that the virus can be cultivated in both stool and saliva, washing hands when changing diapers and taking appropriate hygiene measures in the bathroom could reduce the possibility of an infection.”

Also, it is essential for students to wear a mask when attending school as the study confirmed that viruses are also detected in saliva, the team added.

“Collecting a sample by scraping the inside of the nose with a cotton swab is currently most frequented when testing for Covid-19,” Professor Han said. “However, since a large amount of virus was detected in the stool of adolescent patients for a longer period, stool may be used as another highly reliable diagnostic method to test for Covid-19.”

The journal Emerging Infectious Diseases published the result of the study.