Wuhan uses sample pooling to conduct 6.57 million tests in 10 days

This includes a record 1.47 million tests on Saturday

Wuhan, the city at the centre of China’s COVID-19 outbreak, has conducted 6.5 million tests for COVID-19 in the past 10 days, officials said on Monday following a massive citywide campaign launched on May 14.

The city launched the unprecedented 10 day-campaign to test all of its 11 million residents after a cluster of asymptomatic infections was reported on May 9.

Target of 11 million

Between May 14 and May 23, 6.57 million tests were conducted, the health authority said, falling a little short of the ambitious 11 million target, which is expected to be reached this week. The city still managed to carry out a record 1.47 million nucleic acid tests in a single day, on Saturday, which marked a 15-fold jump in the daily testing prior to the campaign.

The tests, which were free, were carried out by throat swabs in designated locations around the city. Each of the city’s 13 administrative districts was tasked with coming up with a plan, which would first prioritise residential areas where cases had been reported. Children under six were not tested.

The city managed to carry out such a large number by a method called sample pooling, The Wall Street Journal reported. After individual samples are collected, five to ten are bundled and processed in a single nucleic acid test. The entire group is cleared if the test comes out negative. The technique goes back to the Second World War when the U.S. military pooled samples for syphilis screening, The Journal said.

The tests so far have not thrown up a high number of asymptomatic cases. On Monday, 38 new asymptomatic cases were reported and Wuhan now has a total of 326 asymptomatic cases under observation.

Wuhan had completed three million tests in total before the campaign was launched on May 14.