PARIS: As countries emerge from lockdowns imposed to blunt the coronavirus pandemic, dozens have rolled out phone apps to track a person's movements and who they come into contact with, giving officials a vital tool for limiting contagion risks.
The technology could help avert new surges in COVID-19 infections that might overwhelm hospitals battling an outbreak that has killed more than 350,000 people worldwide in just six months.
While many apps and related technologies are voluntary, other governments are enforcing their use, since health experts say at least 60 percent of a population needs to activate them for contact tracing to be effective.
But privacy advocates warn they give unprecedented access to personal data that could be exploited by authorities or even third parties, despite pledges that information will be kept out of reach.
Here is a rundown of the different approaches adopted since the first COVID-19 cases were reported in China last December, and what officials have learned from their experiences.
Asia: Asian countries were the first to roll out tracing apps, with China launching several that use either direct geolocalisation via cellphone networks, or data compiled from train and airline travel or highway checkpoints.
Their use was systematic and compulsory, and played a key role in allowing Beijing to lift regional lockdowns and halt contagions starting in April.
People are ranked green, yellow or red based on their travel history and exposure to infected people, to determine if they can travel or enter public areas.
In Hong Kong and Taiwan, which have managed to limit deaths despite their proximity to China, officials use GPS and Wi-Fi to keep strict tabs on people in quarantine.
India's government launched the Aarogya Setu ("Bridge to Health") app, with more than 100 million downloads since April -- less than one-tenth of its population, since only one in four Indians owns a smartphone.
In Iran, home to the deadliest outbreak in the Middle East, the Mask app is being pushed by officials, though rights groups say the government could be tempted by surveillance possibilities after months of unrest.
Pakistan, for its part, has tapped its powerful intelligence services to deploy secretive surveillance technology normally used to locate insurgents to track coronavirus patients and the people they come into contact with.
Europe: Concerns about privacy protections are particularly acute in Europe, where officials have called for collaborative efforts that would include intense oversight to make sure users know when and how personal data is being exploited.
France, for example, will launch next week a voluntary bluetooth-tracing app that it says will not disclose any personal information, with records erased once the crisis is over.
Britain´s National Health Service is also developing its own system, which is still undergoing testing. In the meantime it is relying on manual tracing, mobilising 25,000 people to contact people who test positive.
Middle East: A number of Gulf countries including Saudi Arabia, the United Arab Emirates, Qatar, and Bahrain have rolled out bluetooth tracing apps -- Doha has even made its use mandatory, warning that violators face up to three years in jail, prompting a rare backlash over privacy concerns.
Israel´s health service in March launched the Hamagen app, Hebrew for "the Shield," which uses a phone´s GPS data and is available in five languages.