China has officially rolled out anal swabs to detect COVID-19 infections as part of its ramped-up nationwide screening efforts to eliminate potential carriers from going unnoticed. The new testing method, which up until now had been via mouth and nose swabs, has made travelers and social media users squirm with discomfort.

A throat swab on a 52-year-old man in Weinan, a city in northern Shaanxi province, showed a negative result after the person showed symptoms such as coughing and appetite loss, a city official said Wednesday, but he tested positive using nose and anal swabs. The person, who had been put in a centralized facility for medical observation as a close contact of another carrier earlier this month, was then confirmed as a COVID-19 patient, the official told a news conference.

Anal swabs require inserting a cotton swab 3 to 5 centimeters (1.2 to 2.0 inches) into the anus and gently rotating it. Last week, a Beijing city official said that anal swabs were taken from over 1,000 teachers, staffers and students at a primary school in the city after an infection had been found. Their nose and throat swabs and serum samples were also collected for testing.

Additional tests using anal swabs can avoid missing infections, as virus traces in fecal samples or anal swabs could remain detectable for a longer time than in samples taken from the upper respiratory tract, Li Tongzeng, a respiratory and infectious disease doctor in Beijing city, told state TV last week. He added that such samples are only necessary for key groups such as those under quarantine.

Stool tests may also be more effective than respiratory tests in identifying COVID-19 infections in children and infants since they carry a higher viral load in their stool than adults, researchers at the Chinese University of Hong Kong (CUHK) had said in a paper published last year.

The new testing method comes amid regional outbreaks and ahead of the Lunar New Year holidays.

Users of China's popular Twitter-like Weibo social media platform reacted to the method with a mix of mirth and horror.

"So lucky I returned to China earlier," one user wrote.

"Low harm, but extreme humiliation," another said, using a laughing emoticon.

Others who had undergone the procedure chimed in with dark humor.

"I've done two anal swabs, every time I did one I had to do a throat swab afterward – I was so scared the nurse would forget to use a new swab," one Weibo user joked.

CCTV said on Sunday anal swabs would not be used as widely as other methods, as the technique was "not convenient."

As cases rise around the world, China has imposed stricter requirements on international arrivals in an effort to keep domestic transmission close to zero a year after it first went into lockdown. The country has also tightened restrictions domestically, with Beijing announcing that people from medium- or high-risk areas will be barred from the city from Thursday to reduce the risk of virus transmission over the Lunar New Year period.

Meanwhile, arrivals into the country must have multiple negative test results and quarantine for at least 14 days in a designated hotel on arrival, with many cities and regions imposing additional home observation requirements.