More than a million Beijing residents undergoing coronavirus testing amid a fresh outbreak have been administered anal swabs, which are considered more accurate and raise the chances of detecting COVID-19, said a Chinese disease specialist.
The key districts of Daxing and Dongcheng began a mass testing drive on Friday after a nine-year-old boy tested positive for the more virulent strain of the virus, first discovered in London and the southeast of England last month.
Health authorities in the Chinese capital said they were aiming to screen more than two million people in 48 hours. Among them, around 1.6 million inhabitants in Daxing were to be given antibody tests, as well as throat, nasal and rectal nucleic acid swabs.
Anal swabs have been in use since last year, including in the major port city of Shanghai, but the method is so far reserved for individuals in potential COVID-19 hotspots, according to an infectious disease expert quoted by China's state broadcaster CCTV on Saturday.
"Since the start of the coronavirus outbreak, we've tested for the virus using mainly throat swabs. Its characteristics are convenience and speed, so it's suitable for large-scale testing," said Beijing You'an Hospital's Li Tongzeng. "Nasal swabs are more accurate than throat swabs, but nasal swabs can be uncomfortable."
He added: "In some asymptomatic cases or in individuals with mild symptoms, they tend to recover from the illness very quickly. It's possible that there will be no trace of the virus in their throat after three to five days.
"What we've found is that in some infected patients, the coronavirus survives for a longer period of time in their digestive tract or excrement than in their respiratory tract."
Li said rectal swabs increase the rate of detectability and lower the chances of a missed diagnosis.
"Of course, anal swabs aren't as convenient as throat swabs, so they're only being used on individuals in key quarantine areas. This will reduce the return of false positives," he added.
According to guidelines published by China's National Health Commission, anal swabs are to be administered 3 to 5 centimeters (1.2 to 2 inches) inside the rectum. The swab is to be rotated and removed before being securely placed inside a sample container.
On Friday, a resident of Tangshan in Hebei province, about 120 miles east of Beijing, told CCTV that she was given double rectal swabs as part of citywide testing in her area. She said each swab took just under 10 seconds.
A few medical papers release since the start of the outbreak last year have suggested anal swabs as a more accurate way of testing for COVID-19, but its merits have yet to be widely accepted by the Chinese medical community.
Wuhan University pathologist Yang Zhanqiu told Communist Party newspaper Global Times on Saturday that throat and nasal swabs remained the "most efficient" method of testing, given that the coronavirus is contracted via the upper respiratory tract.
Beijing's efforts to eventually test all 21.5 million of its residents are expected to continue as it battles its second wave, which began with a cluster of locally transmitted cases in mid-December.
Municipal spokesperson Tian Tao said 17.46 million people in Beijing—roughly 80 percent of its population—have already been tested since the start of the new outbreak.
Residents have gathered in schools, stadiums, shopping malls and public squares for the mass testing drive, which comes at a crucial moment—just two weeks before the country celebrates Lunar New Year, a festive period ordinarily marked by hundreds of millions of commutes home.
China recorded 82 new cases of community infection on January 26, the national health authority said Tuesday. Among them were two locally transmitted cases in Beijing. There were also 56 asymptomatic cases, which China considers separately.
Most of the positive cases were concentrated in the northeast of the country, where tens of millions of residents remain in some form of lockdown in the provinces of Hebei, Jilin and Heilongjiang.
China's total confirmed cases now stand at 89,197. Its death toll rose by one to 4,636 following an additional fatality on Monday.