The app sends alerts to people if its systems have been triggered by someone in their network potentially receiving a positive test.

But the somewhat confusing notification does not necessarily mean that users have to self-isolate. The notification only means that the system is looking at a possible exposure, not that the system has definitely been triggered.

The app's official Twitter account confirmed that users will be sent a specific notification if they are judged to be at high enough risk to need to self-isolate, and that message will be separate from the one indicating that they have been subject to a possible exposure.

Many users of the app – which was released last week – have reported receiving concerning messages on their iPhone or Android phones, which appear to suggest they may be at risk of having been infected with the virus.

“Possible Covid-19 exposure," the notification reads. "Verifying exposure info.

“The app has accessed the date, duration and signal strength of this exposure.”

Given the concerning title of the notification, which reads “possible covid-19 exposure”, many have been concerned that this could mean the app has judged them to be at risk, and that they should self-isolate.

But it is actually the latter part of the message – that the exposure is still being verified – that is important. The notification only means that a potential exposure has been detected, and it is only if a future message arrives that users need to take action.

Apple and Google’s contact-tracing APIs allow phones to connect to other devices and take note of any they come into contact with. If the owner of one of those phones indicates that they have had a positive test, anyone whose phones they came into contact with can then be alerted, and that first notification will be sent.

But further examination of the data is required before people will be told to self-isolate. That will look at further information to judge precisely how likely it is that someone may have been exposed to the person in question – if they are judged to be at risk, that is when they will be given the instruction to self-isolate, in a separate and more straightforward notification.

That second message will include information about what to do when self-isolating, the app’s official Twitter account posted.

“The app will send you an alert if you need to self-isolate and how long for, it'll provide a countdown timer, and when you reach the end of your self-isolation period, you will receive a notification with a link to the latest advice for you,” a representative wrote.