Collecting and analyzing data from devices like smartphones could be crucial for governments in managing the coronavirus outbreak. But these same techniques could also pose serious threats to civil liberties, data privacy advocates say.

Consider countries like China, Taiwan, and Singapore, which have mostly contained the spread of COVID-19 by collecting vast amounts of data to help officials track confirmed cases. These countries along with Hong Kong are examples of governments that have managed to “flatten the curve,” Michele Barry, a Stanford University professor and senior associate dean of global health, said during an online conference about A.I. and the coronavirus hosted by her university on Wednesday.

Singapore was the first country to have the highest confirmed cases out of China, said Barry, but a policy of “strict containment” has led to the city-state avoiding a major increase in new coronavirus cases. To aid this policy, government officials tracked people’s smartphones using GPS technologies to check whether people stayed at home, she said.  

Some Singapore residents were required to take photos “showing they were at home” in order to prove to the government that they were complying with the containment policies, Barry said. 

Meanwhile, China’s coronavirus containment policies involve “unprecedented surveillance,” going so far as using drones outfitted with temperature-tracking sensors to fly over crowds so police could identify people who may have had fevers, she said. In Hong Kong, residents returning from high-risk areas were given tracing bracelets to help officials keep tabs on them to ensure they were being quarantined.

Taiwan has successfully navigated the epidemic largely due to what the country learned from dealing with the SARS epidemic in 2003, explained Jason Wang, director of Stanford University’s Center for Policy, Outcomes, and Prevention. During the SARS crisis, Taiwan created its Central Epidemic Command Center, an emergency control center that lets government agencies better coordinate with each other.

Through that command center, officials were able to link a national health insurance database and an immigration database so that when doctors or nurses saw patients, they were notified whether those patients recently visited high-risk areas like Wuhan, the Chinese city at the center of the COVID-19 outbreak. With that information, health care staff could know whether they had to take any other precautionary measures like wearing protective gear that could limit their chances of contracting the virus, Wang said.

Despite the success these Asian governments have had managing the pandemic, Barry acknowledged that the data-tracking methods could prove hard to swallow for Western countries like the U.S., which tend to value individual privacy. 

Authoritarian governments, Barry said, rarely “unroll strict laws” after they’ve debuted.

Human rights organization Amnesty International is concerned about that problem. Michael Kleinman, the group’s Silicon Valley Initiative director, cited a policy in China that requires citizens who want to participate in the broader economy to download an app, referred to in Chinese media as Alipay Health Code, that assigns people certain colors like green, yellow, and red that determine whether they must be quarantined. The problem is that the “Chinese government has not shown how it works,” he said, adding that the information the app collects is shared with the police. 

Amnesty International worries that monitoring programs will be left in place long after the coronavirus pandemic subsides.

Wang noted that at least in Taiwan, the country’s various data-tracking and sharing policies are set to expire a year from March. Any personal data like travel history that its command center collects during the coronavirus pandemic will eventually get destroyed, Wang added.

Kleinman acknowledged that Amnesty International is still in its early stages of learning about each country’s specific data policies, so the group can’t comment about every government’s tactics. But generally, Amnesty International said, that if government officials say they will roll back certain policies after a specific amount of time, they need to be transparent so that third parties can verify their claims. 

Adam Schwartz, a lawyer for the digital rights group Electronic Freedom Frontier (EFF), told Fortune that his organization is reviewing government data-tracking policies that are better for privacy, including Singapore’s use of Bluetooth technologies. Some researchers say that using Bluetooth, a wireless technology standard, instead of GPS to track the spread of coronavirus, would keep the government from collecting personal details about individuals.

“We are studying that closely,” Schwartz said, but added that the EFF is “not yet persuaded” by current evidence.

Asked whether there are any examples of governments rolling back surveillance policies after a crisis recedes, Schwartz couldn’t recall any.

“That is exactly the problem,” Schwartz said.

Story updated on April 3, 5:30 PM ET to clarify information about the app that concerned Amnesty International.

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