A first-person view inside Beijing's COVID-19 tests

As the number of COVID-19 cases climbed in Beijing in recent days, officials identified more than 350,000 people who needed to be tested. I was one of them. | Workers in protective suits prepare to administer a coronavirus test.

After word first emerged of a cluster of cases at a sprawling wholesale market in the Chinese capital, I had gone to the area to take photographs.

Although I never entered the Xinfadi market and only took photos from nearby streets, unknown to me, I had been flagged as a potential vector for the virus. | Workers in protective suits take the temperatures of people at a COVID-19 testing site

My phone rang on Wednesday afternoon. An official from my neighborhood's community association informed me that I should shortly report to the gates of a nearby sports stadium to be bused to a coronavirus testing site. | Workers in protective suits review paperwork at a COVID-19 testing site.

The caller did not know my name, but they knew that someone associated with my cellphone number had been in the vicinity of the market. I may have been tracked through my cellphone. A Beijing city official said Wednesday that 355,000 people have been identifed for testing via big data, but he did not specify how.

Several dozen people milled about at the meeting point, eyeing each other suspiciously and staying apart. A few wore multiple face masks on top of each other. After checking in, we were escorted to buses _ one person per row. | People wait in line at a COVID-19 testing site after they were ordered by the government to be tested

The buses took us to a large city park, where the grounds of a museum had been converted into a temporary testing site. Hundreds of people were already in line. Many said that, like me, they had not visited the market but just been in the area. Some complained that they had merely driven past on a highway.

An official with a loudspeaker ordered people to spread out, but the size of the crowd and the length of the line led to people inching together.

I looked around with some worry - was I standing among Xinfadi workers or daily customers? I had not felt in danger photographing the market from a distance, but packed among people who had been flagged as a virus risk, I felt a bit unsafe.

Eventually I reached the front of the snaking line. A worker in full protective suit and face shield took my temperature and checked my Beijing Health Kit app. For months, scanning the app's QR code and showing your results has been a constant of daily life in Beijing.

I showed him my green code, indicating "No Abnormal Conditions,'' and was directed to a row of tables to register for the test. | A vial for a coronavirus test is seen at a COVID-19 testing site.

I was handed a bar-coded vial and waved into a large hall, where a half-dozen tables were set up with a pair of workers in protective suits at each one. I sat down in a chair and was instructed to tilt my head back and say "aaah". The instinct to gag was strong as a worker waved a swab across the back of my throat. | A worker in a protective suit swabs the throat of a man at a COVID-19 testing site.

"Okay, finished", said the worker in English. On the bus ride back, the mood was considerably lighter. People who had sat in stony silence on the ride out hours earlier chatted with each other about the virus outbreak in other countries and the merits of different brands of cellphones.

Back at our meeting point, we parted ways with a warning to stay at home until we received our test results. With hundreds of thousands of people ordered to self-quarantine, it would seem difficult to enforce. But needless to say I plan to stay at home.