Explainer: How Wuhan tested 6.5 million people for coronavirus in '10-day battle'

Wuhan, the epicentre for coronavirus in China, has been fearing a second wave of the virus after a cluster of cases was detected. After six new cases were detected in a residential complex, Wuhan, on May 11, announced its plan to conduct a widespread testing campaign on all of Wuhan's population free of cost. Swab test samples were collected from more than nine million residents from May 15 to May 23, China's state-broadcaster CCTV reported. 

Authorities took swift action and within less than two weeks the city, with a population of 11 million people, collected more than 9 million samples and tested 6.5 million in what is considered as the largest testing campaign ever. This is almost three times as large as the testing campaign of the United States which has only tested 14 million people in 4 months. 

What are nucleic acid tests?

(Image credit: Twitter/@EducateRohingya)

Nucleic acid tests detect the virus' genetic code and help detect the virus at early stages, as opposed to the tests that examine a body's immune response. It is a molecular technique that screens blood donations to reduce the risk of infections. The test is carried out from nasal/throat swab sample from individuals. The test has been developed and successfully demonstrated using synthetic templates and is rapid, cost-effective and accurate.

While Wuhan’s testing campaign has been widely lauded, some experts reportedly believe that since the nucleic acid tests difficult to administer even in hospitals under ordinary circumstances, trying to conduct them in makeshift tents in quick succession can give many erroneous results. Another problem with such large scale testing in a short period is that it tends to overwhelm the medical staff. 

Read: Explainer: As Sweden Attempts To Achieve Herd Immunity Against COVID, Here's What It Means

How Wuhan tested 6.6 million people in 10 days?

Wuhan ended its 76-day lockdown on April 8 and transportation, businesses, parks, and restaurants reopened as the city restored normalcy. For 35 days, the city reported no new case but in early May, six cases were recorded prompting fear of resurgence. Hailed as "10-day battle" by local authorities, the speed of testing has left people across the world amazed as it is way more than many big countries.

Elderly were among the first to be tested as they are at most risk, followed by those living in densely populated areas and communities with large migrant populations. Children under six are not advised to take the tests. Here's how Wuhan tested 6.6 million people in 10 days. 

(Image credit: Twitter/@kashibondu)

Increased testing capacity

To conduct the massive testing campaign, sampling booths were set up across the city and people in large numbers lined up for swab tests. The country mobilized thousands of medical workers and spent hundreds of millions of dollars. The city increased its testing capacity significantly from processing around 46,000 tests a day before the drive, to as many as 1.47 million tests later. On May 22, Wuhan conducted 1.47 million tests and on May 23, authorities set up 231 extra testing booths to ensure everyone gets tested, according to the Changjiang Daily, the official Communist Party mouthpiece in Wuhan. The city conducted 11,46,156 nucleic acid tests on May 23.

(Image credit: Twitter/@xurde0o)

Door to door visit

The healthcare workers even paid door to door visits to collect samples of elderly and specially-abled citizens. Announcements were made on loudspeakers and in some cases, the government even reportedly threatened to downgrade health cards and ban people from entering grocery stores if they are not tested.

“If you do not participate, you will not be allowed to enter supermarkets or banks,” the announcement said. “Your green code will turn yellow, which will cause inconvenience to your life.”

Read: COVID-19: Wuhan Tests 6.5 Million Residents In 9 Days Amid Fear Of Second Wave

(Image credit: Twitter/ @RustyFact)

Makeshift testing tents and online appointments

Makeshift tents have been set up at various places and in schools in order to allow people to line up. Citizens can take appointments online and each resident was given a time slot to avoid crowding. Authorities ensured that these large-scale tests do not become a source of infections. The tests were conducted in open spaces and all the residents had to wear face masks, have their temperatures screened and maintain distance from one another.  

(Image credits: Twitter/@ChinaScience)

Pool Testing Method

The city’s health authorities did ‘pool testing’, combining some of the samples taken from multiple individuals together and testing them in a single tube, to save time. As per reports, if a tube tested positive, authorities carried out extra tests on each individual to find the positive sample. If the full batch comes back negative, it can be discarded.

The recent tests identified 198 asymptomatic cases in Wuhan, the state-run Health Times reported. China has reported one new confirmed coronavirus case and 28 asymptomatic infections, health officials said on May 27. Of the 28 new asymptomatic infections, 22 were reported from Wuhan, taking the total number of such cases to 404, the NHC said.

Asymptomatic cases pose a problem as the patients are tested COVID-19 positive but develop no symptoms such as fever, cough or sore throat. However, they pose a risk of spreading the disease to others. As of May 27, China has 82,993 confirmed cases, of which 78,280 have recovered while 4,634 people succumbed to the disease.

Read: Explainer: What Does False Positive And False Negative Coronavirus Test Results Mean?

Read: Explainer: As Countries Ease Lockdown, Here’s Why 2nd Wave Of COVID Is A Serious Concern