The study shows that traces of the virus in stool samples remain detectable for longer and can provide more accurate test results.
Some Chinese cities are using samples from the anus to detect potential COVID-19 infections, while China is stepping up screening to make sure no potential carrier of the new coronavirus is missed before the New Year holidays next month, when tens of millions of people are typically present are traveling home to their families.
China has fought new cases of the north and northeast with strict lockdowns and mass tests to stamp out the outbreaks.
A city official in Weinan, northern Shaanxi Province, justifying the decision to take anal swabs, said a 52-year-old man with symptoms such as coughing initially tested negative for COVID-19. He was then tested with an anal swab.
The man who was locked up in a central medical observation facility earlier this month as the close contact of another COVID-19 patient was then confirmed to have the virus, the official told a press conference.
For anal swabs, a cotton swab must be inserted three to five centimeters (1.2 to two inches) into the anus and gently twisted.
In an online video from the state-sponsored Global Times newspaper, Zhang Wenhong of Huashan Hospital in Shanghai said such swabs could be useful in minimizing the risk of relapse after recovery.
“Traces of the coronavirus can be detected in the faeces and in the intestines of the abdominal cavity,” Zhang was quoted as saying in the report.
Last week, a Beijing city official said that more than 1,000 teachers, staff and students at an elementary school in the city had anal swabs taken after they were found infected. Nose and throat swabs and serum samples were also taken for testing purposes.
Additional tests with anal swabs can detect infections that other tests miss because traces of virus may remain detectable in stool samples or anal swabs for longer than in upper airway samples, said Dr. Li Tongzeng, a respiratory and infectious disease specialist in Beijing City, told state television last week.
Li added that such samples are only necessary for key groups like those under quarantine.
“Little harm, extreme humiliation”
Stool tests may be more effective than breath tests at identifying COVID-19 infections in children and infants because they have a higher viral load in stool than adults, researchers from the Chinese University of Hong Kong (CUHK) found in an article published last year.
The users of China’s Weibo, its Twitter-like social media platform, reacted to the method with a mixture of joy and horror.
“So happy I returned to China early,” wrote one user.
“Little harm but extreme humiliation,” said another with a laughing emoticon.
Others who had undergone the procedure interfered with dark humor.
“I did two anal swabs, each time I did one I had to get a throat swab afterwards – I was so scared the nurse would forget to use a new smear,” joked one Weibo user.