BERLIN (Reuters) – Germany sought to mobilize the public on Tuesday to download a new smartphone app that seeks to help break the chain of coronavirus infections, one of several such apps in Europe that governments hope will revive travel and tourism.

The new Covid-Warn-App, which became available for download for Apple and Android phones overnight, uses Bluetooth short-range radio to monitor close contacts between people and issue a warning should one of them test positive.

“Everyone who downloads the app, and everyone who encourages friends to do so, is making a difference,” Health Minister Jens Spahn told ZDF public television ahead of a launch event in Berlin.

Germany follows European countries like Italy, Poland and Switzerland in launching an app based on technology from Apple and Alphabet’s Google that protects privacy by storing Bluetooth logs securely on devices.

The project nearly went off the rails in April as Berlin abandoned an initial approach that stored data on a central server – which privacy experts said could allow people’s relationships to be spied on.

Still, public enthusiasm for the app is moderate – last week’s Politbarometer opinion poll for ZDF found that 42% of people would download it and 46% would not, while 8% didn’t have a smartphone.

Millions of downloads will be needed to increase the chance of both people in a risk event having the app, but officials have backed away from earlier aspirations to reach as much as 60% of the population.

Downloading the Covid-Warn-App was easy enough on an iPhone on Tuesday morning, although some people may be deterred by the need to upgrade first to the latest version of the iOS operating system.