Millions of people in the UK are to be asked to use a phone app to help stop the spread of coronavirus.

The Government is “optimistic” people will download the app to allow better contact tracing – a key factor in beating Covid-19 and helping the country out of lockdown.

Communities Secretary Robert Jenrick said he thought the “vast majority” of people would download the app and “play their part” – but insisted it was just one element of the plan to stop the spread.

The app would use Bluetooth to log each time it comes into close range of other devices also running the app.

If someone develops symptoms of Covid-19, they can use the app to inform the NHS, which will then trigger an anonymous alert to any other app users the infected person came into contact with by analysing the collected logs.

Here, the PA news agency looks at how other countries have been using mobile technology in the fight against Covid-19:

– Australia

Australia released COVIDSafe last Sunday evening and more than four million people have started using the app.

Use of the app is voluntary, but the government said 40% of Australians, or 10 million people, need to use it for the program to be a success.

Speaking ahead of the weekend, Australian Prime Minister Scott Morrison said more people downloading the app would speed up the reopening of pubs, adding: “If that isn’t an incentive for Australians to download COVIDSafe on a Friday, I don’t know what is.”

– New Zealand

Across the Tasman Sea and New Zealand is also planning an app to help with contact tracing, but Prime Minister Jacinda Ardern said it would have to be part of a number of measures.

She told reporters: “We are working on it but I have to say our big focus has been getting our in-person contact tracing right, because we will all still be relying on that.”

– Singapore

Developers of the TraceTogether app estimate around one in five people in the city state have downloaded the app, the first Bluetooth contact tracing app in the world.

Half of the 1.1 million downloads of the app came in the first 24 hours.

– India

The Aarogya Setu app uses both GPS location and Bluetooth to track users and has been downloaded 50 million times. It is voluntary for Indian citizens, but the government made it mandatory for all of its employees to download to app and use it last week.

– China

China’s app gives users a colour based on a traffic light system – green for clear, red for a coronavirus contact – and it is reportedly needed to move about as widespread restrictions are lifted.

– South Korea

South Korea sits apart from others on the list as it has not used an app-based solution to trace potential contacts. Instead, authorities have tracked people using a number of sources including mobile device tracking and financial transaction information to alert potential contacts.

– Elsewhere

The Czech Republic has released an app similar to the one from Singapore, while North Macedonia’s StopKorona! app uses Bluetooth. Smittestopp in Norway uses both GPS and Bluetooth, while apps are also in development in Italy, Austria and Germany.