Backed by an expansive and efficient network of nucleic acid testing facilities, the rollout of fast and widespread screening has become the default response to new clusters of COVID-19 infections in China.
The robust testing capability has enabled the country to track down and isolate infected cases－with some at an asymptomatic stage－and curb fresh outbreaks at a faster pace, health officials have said.
Less than 10 days after a new outbreak was detected on July 15 in Urumqi, capital of Xinjiang Uygur autonomous region, the local government said it had taken over 2.3 million samples and initiated the second round of a free testing program in areas at a higher risk of infection.
In Liaoning province's Dalian city, where a new cluster tied to a seafood company emerged last week, more than 1.2 million samples were collected on the first day of a citywide testing blitz expected to be completed in four days.
Meanwhile, laboratories in Beijing, Fuzhou in Fujian province and Zhuhai in Guangdong province have also sprung into action to test entire neighborhoods where isolated cases were registered.
Zhang Wenhong, head of the infectious disease department at Huashan Hospital in Shanghai, said the prompt rollout of mass testing has underpinned China's disease control strategy that aims to detect all infections and bring the number of new cases down to zero quickly.
Taking the recent outbreak in Urumqi as an example, Zhang said the rapid expansion of tests, coupled with targeted containment measures, may stem the flare-up of the virus and allow resumption of normal activities in three to four weeks.
"As sporadic outbreaks continue to occur, such an approach is the optimal solution for China at present and may offer a point of reference for the international community," he said in a Weibo post.
The swift testing work stands in contrast to the delays and shortages experienced during the early stages of the domestic epidemic, which hit Hubei province the hardest. To cope with an overflow of patients who cannot access tests but demand immediate treatment, China decided to add a new group of confirmed cases based on doctors' analysis and lung imaging, known as "cases of clinical diagnosis".
This category was soon scrapped in late February after national resources were mobilized to aid the region's testing efforts.
"The new diagnosis method is only an interim measure aimed at hospitalizing all patients and reducing mortality rates," Wang Guiqiang, head of the infectious disease department at Peking University First Hospital, said during a news conference in February.
"As testing capability has caught up and all suspected cases can now receive quick diagnoses, we've decided to drop it."
The technology used to develop tests for the virus is not complicated and relatively mature, according to Peng Zhiqiang, deputy director of the Guangdong Provincial Center for Disease Control and Prevention's infectious disease unit.
"The key to boosting tests is exhausting all means to set up laboratories, gathering and allocating equipment and reagents, and training sufficient medical personnel to run tests," he said.
Mobilizing regional and even national resources to assist in local testing has been an essential approach amid the epidemic in China.
In Urumqi, less than 72 hours after the latest COVID-19 outbreak was detected, 10 medical aid teams were dispatched from across China to aid testing.
During a visit to Dalian last week, Health Minister Ma Xiaowei also stressed tapping into the potential of local testing institutions while making use of resources in nearby cities to cut turnaround times of mass testing.
Wang Xinming, a technician at the Chinese Academy of Medical Sciences and Peking Union Medical College who had participated in several aid missions, said laboratory workers are now armed with an "on-the-go" mindset.
"To prepare for sudden outbreaks, we have stocked up on consumable equipment, and all laboratory workers are on standby. We are ready to set off any time," Wang said.
"Upon being dispatched to a hospital, we will coordinate with local health workers and smooth out working procedures, which will help yield results more quickly," she added.
Absorbing lessons from the initial wave of outbreaks in Hubei, China has also stepped up local preparedness by enhancing infrastructure and training.
As of late June, China is capable of conducting nucleic acid tests on 3.78 million people per day, up from 1.26 million in early March, according to Guo Yanhong, an official with the National Health Commission's medical supervision and administration department.
The number of testing facilities more than doubled from 2,081 in early March to 4,804 in late June, and the number of testing personnel stood at over 28,000 nationwide, according to Guo.
"To teach a health worker how to conduct tests only takes a few days, but their roles in ensuring the speed and precision of nucleic acid tests are crucial," Wang said.
"Before wrapping up our work in Jilin, Jilin province, which was hit with an outbreak in May, we trained laboratory workers from three local hospitals on performing tests. They have now obtained certificates to run tests independently for the novel coronavirus," she said.
Peng, from Guangdong province, said with current stockpiles of equipment and personnel, meeting the national requirement of reporting test results to people visiting fever clinics within six hours is easily within reach.
However, even with a significant ramp-up in testing capacity, abrupt outbreaks affecting a large population may result in temporary shortages.
Guo, from the National Health Commission, said that during the recent outbreak in Beijing tied to a wholesale food market, demand had outpaced the capital's testing capability for a short period.
"To address the testing shortage, 20 testing teams from 12 provinces were dispatched to Beijing," she said. "We also deployed mobile laboratories and carried out mixed testing in low-risk groups to increase efficiency."
The mixed testing method, which typically involves blending five samples together for tests, is projected to raise the number of samples being processed per day in Beijing from 400,000 to 1 million per day, according to Guo.
A noticeable outcome of mass testing is a growing pool of asymptomatic cases, which would have gone unnoticed because they lack symptoms.
In the past week, Urumqi has detected from 13 to 38 asymptomatic infections on a daily basis. As of July 29, 143 symptom-free virus carriers are under medical observation.
Zhang Wei, director of the city's health commission, said all asymptomatic cases were identified through the free, citywide screening effort.
"Some of them are in an incubation period now and will be re-diagnosed as confirmed cases later," he said. "The earlier we confirm cases, the faster can we deliver treatment and alleviate their symptoms."
Wu Zunyou, chief epidemiologist with the Chinese Center for Disease Control and Prevention, also said during an interview with China Central Television on July 29 that in Dalian, the majority of confirmed cases have been found in previously asymptomatic patients that were already under medical observation.
"That means these new cases are under the management of local health authorities and will not cause wider transmissions," he said.
