Singapore has asked its citizens for help. Half a million people reacted within the first 24 hours.

A new app – TraceTogether – lets the government use citizens’ smartphones to see whether they have been in proximity with someone infected with the novel coronavirus Covid-19.

The app uses Bluetooth signals to record when citizens come within Bluetooth range of another app user.

These records are stored on citizens’ phones. If they fall ill with Covid-19, contact tracers can use these records to alert other people at risk.

The service was built by the Government Technology Agency of Singapore, the Ministry of Health and the new SGUnited initiative.

Jason Bay, the Senior Director at GovTech who led the tech development, said that: “By alerting you sooner, you can avoid inadvertently transmitting the virus to those around you, including your loved ones and family,” on a public Facebook post.

“Since the virus appears to be capable of asymptomatic or mildly symptomatic transmission, we may not know that we may be carriers of the disease until after transmission has occurred.”

The process of finding people at risk of illness, called contact tracing, is highly manual and relies on people remembering who they met with days later. This new app aims to solve that problem, Senior Minister of State Dr Janil Puthucheary told a press conference yesterday. It crowdsources the response to Covid-19, ensuring that MOH contact tracers receive data faster to keep people safe.

GovInsider understands that GovTech is planning to make this an open source platform, which means that the code will be available for other governments to use.

Singaporean officials also told GovInsider that they would be willing to support international organisations who want to use the same technology to battle community spread within their own countries.

The app is an experiment in trust because it logs who users are meeting with. However, GovTech moved to clarify some questions around privacy.

The data is stored only on the users’ local device, according to an official press release. It will be accessed by the Government only in the case that someone contracts Covid-19.

The app does not send any data to government servers, officials have said. Citizens have used packet scanning technology to show that it does not communicate with any government systems.

“When requested by [Government], users can send their TraceTogether logs to facilitate the contact tracing process. Up to that point, the authorities, including MOH and GovTech, have no knowledge of the user’s TraceTogether data. The TraceTogether logs are only deciphered and analysed after the user sends the information,” according to the official press release.

Reports have noted that the app requires location permissions on Android devices. However, officials said that Google requires this for any Bluetooth connections “because Bluetooth can be used to derive location information when combined with beacons in fixed locations”.

This approach provides greater consent and anonymity than measures being taken in some other countries. Israel, for instance, has authorised its anti-terrorism agency to track the movements of all Israeli citizens using cellular data, Bloomberg reported.

“These means will greatly assist us in locating patients and thereby stop the spread of the virus,” the Israeli Prime Minister said.

Wuhan, the Chinese city where the disease first emerged in large numbers, has used drones to monitor the streets and ensure that people stay in their houses.

TraceTogether is available on the App Store and the Google Play store.