On a sunny day in late March, Takako Hiruma was walking through Aberdeen, a township next to a fishing harbor on the southern side of Hong Kong island. Across the street, Hiruma saw a man sneeze and noticed he was wearing a face mask and a quarantine bracelet, a measure the city introduced in early February to keep track of recent arrivals from countries at high risk of COVID-19. The bracelet had been trending on social media, so she recognized it right away.

Hiruma has lived in Hong Kong for seven years, and, worried about the safety of the many old people in Aberdeen, she took a photo of the man and called 999, the police emergency number. While he kept “roaming around, looking at his phone, stopping, texting, and walking,” Hiruma followed him. “I didn’t want to get too near or make it too obvious I was following him, so I just kept updating the police. He’s in this area, he’s now moving, he’s going across the road.” She trailed him to a restaurant called Cafe de Coral, which is where police approached him. Hiruma doesn’t know what happened next, but Hong Kong had seen a large uptick of cases that week, and people were paranoid. “He should be staying in his place,” she said, “not going out. So, I had to report him.”

Hong Kong’s coronavirus containment efforts have relied heavily on testing, tracking, and individual reporting. As of May 4, 2020, the government had sent 173,228 people into quarantine and distributed 82,000 wristbands. Four people have been jailed for violating the rules, and 56 are being investigated for trying to flee the city. If citizens see somebody breaking quarantine, they are encouraged to call local police or a government hotline or file a complaint via an online platform. And people have also been taking public safety into their own hands.

Another episode occurred two weeks after the Aberdeen incident in the Mid-Levels, a residential neighborhood of towering apartment blocks not far from Hong Kong’s Central district. A woman who wanted her name withheld for professional reasons said that she’d just finished work and was buying ice cream at her local supermarket when she noticed a man in his 30s standing right behind her, holding up his phone. At first, she thought he was making a video call, but then she realized he wasn’t wearing any headphones — and he was looking directly at her.

She turned and asked whether he was following her, to which he answered, “Aren’t you supposed to be at home?” He then mentioned her tracker. After her initial surprise, she realized he was looking at her Garmin GPS watch. She showed it to him and explained that it wasn’t a tracker. And that she wasn’t doing anything wrong. He apologized and told her, “I thought you were one of those people breaking their quarantine.”

Similar scenes have played out across Hong Kong over the past few months, as people in the streets, stores, and apartment towers of this global financial hub work to ensure that no one flouts the mandatory quarantine order. That confines residents returning from travel to two weeks in their homes or hotel rooms, with no option of leaving. And Hong Kongers have been taking it very seriously. One of the major supermarket chains, Park’n’Shop, even put notices on its doors warning wristband wearers to stay away and threatening to report offenders to authorities.

The apex of corona vigilantism may have been on March 23, when a 13-year-old girl with a wristband was taped eating dinner and walking around the town of Sha Tin with an older man. With a recording device in hand, a fellow diner stopped the “escapees” from getting into a taxi and followed them to the nearby Courtyard by Marriott hotel. The video was posted on Facebook, YouTube, and Twitter and was picked up by the Hong Kong–based media outlet South China Morning Post, where it netted 325,000 views. Of the 1,200 comments, a few people complained that the teenager should have been reported to authorities instead of being doxed.

The bulk of commenters applauded the brave and heroic “corona police” for exposing her and her companion. “I just can’t understand how come some people are so selfish/ignorant. Like it’s only 14 days not 14 years. How can you not stay inside for 14 days to save yourself and others,” a woman named Babette Radclyffe-Thomas wrote on Twitter. Within hours of the Sha Tin video being posted, the offending girl and her uncle were sent to a government quarantine facility.

This special administrative region of China shares a border with the mainland, and its first COVID-19 patient arrived via high-speed rail from Wuhan on January 21. Hong Kong is one of the densest cities in the world — it has 17,000 people per square mile — and clusters soon emerged within the skyscrapers and colonial-era tenements. A family sharing a hot pot meal in Kwun Tong were among the first, but others were linked to a Buddhist temple in North Point and a karaoke bar in Tsim Sha Tsui.

Since early February, Hong Kong has allowed arrivals from mainland China and other high-risk countries to go into home or hotel quarantine, but some have ignored the restrictions, prompting the city’s health authorities to send out more than 400 warning letters. When the outbreak spread overseas in mid-March, thousands of Hong Kongers flew home each day, triggering a second wave of infections. Members of a band that had performed in the nightlife area of Lan Kwai Fong fell ill, as did guests at a wedding in Discovery Bay, a 25-minute ferry ride from Central. Both these clusters are thought to be linked to overseas arrivals, said Benjamin Cowling, head of epidemiology and biostatistics at the University of Hong Kong. At this point, the city had reported 192 COVID-19 cases and four deaths.

On March 19, authorities ordered all arrivals into mandatory quarantine and distributed monitoring wristbands printed with QR codes, similar to the ones used at concerts. Anybody who left their home or removed their tracker risked prosecution. Farah Siddiqi, co-founder of the 6,800-person-strong Hong Kong quarantine support group on Facebook, said that, right away, there were technical problems. Some trackers barely worked. In one instance, the Wi-Fi in a bedroom was so weak that “authorities picked up a returnee and took her to a quarantine facility,” Siddiqi said. At the same time, debate arose over whether the devices actually did any tracking. “Ironically, in Hong Kong, our main gripe about the so-called trackers is that they did not work properly,” said Wilson Leung, a member of the Progressive Lawyers Group. They seemed “quite easy to fool,” and people were often seen wearing them outside, he said.

On March 31, authorities switched from the bracelets back to the electronic wristbands, which is what I received several weeks later when I was one of nearly 500 residents returning to Hong Kong. (In April of last year, the city averaged around 200,000 arrivals each day.) Upon boarding the plane in Sydney, crew members handed out compulsory quarantine orders, which laid out the rules about the trackers. As with the earlier models, any attempt to go outside or tamper with the device, which was produced by a local startup called Compathnion, could lead to a fine of around $3,225 and six months of jail time.

After landing at the Hong Kong airport, I downloaded the StayHomeSafe app and paired it with the tracking device, which was so big it dwarfed my iPhone. Once I got home, I activated the “geofencing” setting. Suddenly, my phone was using the surrounding GPS, Wi-Fi, telecom, and Bluetooth signals to set up a virtual boundary. Any breach of that boundary would alert health authorities and the police.

After three days of quarantine, I received a text message informing me that my location had been checked 127 times. Over the entire two-week period, I got four phone calls from authorities and a surprise visit from two firemen. I also received random requests to scan a QR code — a way of ensuring I was staying inside. But the biggest intrusions were the video calls, which government officials would make without warning. As of May 4, the government had made 14,000 such “surprise visits” and 390,000 phone or video calls to people in quarantine.

Given recent concerns over surveillance of the city’s protest movement, Hong Kong’s zero-tolerance approach to COVID-19 might seem as if it would be controversial. Instead, the trackers have been met with widespread approval. While there are no polls specific to Hong Kong, neighboring Asian nations have won strong public support for following similar strategies. A study commissioned by Seoul-based TV and radio broadcaster TBS showed that nearly eight in 10 South Koreans were in favor of quarantine wristbands. And the first cohort of “graduates” from the HK Facebook quarantine support group celebrated the end of their two-week lockdown by posting photos of themselves trying on shoes and cutting off wristbands. Cowling, the epidemiologist, attributes this positive response to a mix of practical and cultural elements, including a strong sense of civic duty, which encourages people to act in the best interest of their community. But perhaps the most significant factor is the recent memory of the SARS outbreak, which killed nearly 300 people in 2003. Soon after COVID-19 began to spread in Hong Kong, old SARS-era habits resurfaced. Temperature checks and face masks in public became the norm once again, and hand sanitizer returned to lobbies. 

Still, Leung says that if trackers were introduced now, when infection numbers have dropped, citizens would be more concerned about privacy. As time passes, he says, “We see more and more instances of the Hong Kong authorities apparently using emergency COVID-19 measures to suppress protests and dissent.” (China is also using this moment to try to establish its authority over the semi-autonomous territory. After nearly a year of pro-democracy protests, Beijing announced last week that it would consider imposing new national security laws on the city.) For its part, Hong Kong’s Innovation and Technology Bureau says the wristbands are not equipped with GPS, the app does not take data from phones, and, at the end of quarantine, users can simply delete the app and throw away the trackers. And as the number of new cases continues to drop — many days there are zero reported — so has the incidence of corona-shaming videos. The reality of a global pandemic is forcing citizens to consider the trade-offs between health and privacy, and many are leaning toward the former. “Recently, people have preferred to have the tracker over having to go to a quarantine facility,” says Siddiqi, “and have been asking our group why they couldn’t get one.”

Whatever one’s feelings about the trackers, Hong Kong’s efforts have worked. The city has largely stayed open for business, and, along with Taiwan, it is leading the world in containing the virus. This city of 7.5 million people has seen 1,064 COVID-19 cases and four deaths; by comparison, New York City has 8.3 million people and has experienced 16,232 deaths. Bars, schools, and libraries are reopening; government workers have returned to offices, and some people from mainland China are allowed in for school and essential business. But testing, quarantine, and trackers are likely to become the new norm until there is a vaccine, effective antivirals, or a drop in overseas cases. And as the past few months have demonstrated, it’s a norm that will take some getting used to.