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Corona warning app: Questions and answers about the German tracing app

In earlier versions of the Corona warning app, the automatic risk assessment in the background on some Android smartphones was interrupted because the operating system put the app into sleep mode as soon as it was no longer opened regularly. The sending and receiving of the pseudonymized IDs continued to work. Because the special Bluetooth interface from Google is responsible for this.

What are QR codes in the Corona Warning app from version 2.0 for?

The Corona Warning App 2.0 was published on April 21, 2021. It now enables you to scan QR codes of events, restaurants and shops, which is also known as "check-in". The codes are created by the shopkeepers or organizers. However, the app is not suitable for fulfilling the contact details required in many federal states. Because the Corona-Warn-App still does not save any personal data such as name, address, e-mail and telephone number. This means that no health department can contact you.

But with the new function you increase the likelihood of being warned of an increased risk of infection. Technically it works like this: The data of your check-in are saved locally on your device for 14 days. If someone reports a positive Covid-19 test result in the app, their check-in data and IDs are transferred to the server of the Corona app and distributed to the other Corona warning apps. If there is a match with your check-ins, you will receive a red or green warning. The color depends on how long you have been in the same place with the infected person: if it is less than 10 minutes, the tile stays green. In the contact diary, you can see whether a low or high risk encounter is an event-based warning.

In the developer blog for the Corona-Warn-App you can see in a video how you can share information to warn others.

What is the rapid test profile from version 2.2?

With the update to version 2.2. the Corona-Warn-App got the possibility in mid-May 2021 to activate a Quick test profile to put on. This means that you can enter your personal data name, date of birth, postal address, telephone number and email address in the app. A QR code is then created from this, which can be scanned at the test centers. This speeds up the registration process there, because you do not have to enter or name your data there by hand. However, this only works for stations that no own appointment booking system and also support the QR code of the Corona warning app. The participating organizations are listed here.

None of the fields in the Corona-Warn-App is a mandatory field - so you do not have to enter all of the information there. What you leave open, you have to state at a test center. The data is required there so that it can be forwarded to the health department in the event of a positive test result. This is why you always have to show your identity card to confirm your data.

The data entered will be only saved on your smartphone. This means that it is not possible to steal it, e.g. by attacking a server - a difference to apps like "luca", which are used to track contacts. Once a profile has been created, you can also remove it again. Creating the profile and showing the QR code at the test sites is voluntary.

I received the message that I had contact with someone who tested positive. What does that mean in concrete terms?

The Corona warning app only informs you that you have had contact with a person who tested positive, while this person was in all likelihood contagious. That doesn't mean you actually got infected, however, that there is a risk.

However, the warning about the risk of infection does not imply any obligation, e.g. to stay at home. Those affected are also not obliged to report the warning, for example to the health authorities. However, the app then recommends that you report to the health department. The medical on-call service by telephone is also an alternative 116 117 or your family doctor.

If you have received a warning, you should still behave particularly cautiously and, as far as possible, in domestic quarantine go. However, this is just a recommendation. Tips on how to behave in quarantine at home can be found here in a separate article.

App users who have received a warning are not automatically entitled to a corona test. It is best to discuss with your doctor whether a test is appropriate Family doctor.

The app shows risk encounters, but stays green. Why?

The green indicator means there is a low to no chance that you have contracted COVID-19 from someone. Ideally, the Corona warning app shows in a green box: "Low risk, so far no risk encounters". But there are also cases in which the app shows risk encounters, but still remains green. The reason lies in how the algorithm calculates the risk of infection. The developers at SAP and the Robert Koch Institute explain this in this blog post, for example, and explain an adjustment in this post in February.

Put simply, it depends on how long A person reported as infected how close arrived. The number of risk encounters displayed are, for example, people with a positive test result (who also reported this in the app) whom you have met in the past few days. But it can also be a person you have met several times.

Whether the app shows a red or green risk depends on how close you got to infected people or how long you were near them and how much time there is between the encounter and the test result. Among other things, the app adds up the length of time in which you have come very close to people with a high risk status.

Since version 1.9, the app has been filtering out low-risk encounters. This should reduce the number of reports of low risk encounters.

My risk status has changed. Does the app show me why?

The Corona-Warn-App does not show you which contacts, when and where your risk status was increased. You could possibly determine this yourself by keeping the contact diary (see next point). Since version 1.14.3, however, the app should show if there is an increased risk,

  • whether your status has changed because of one or more high-risk encounters or
  • whether your status has changed due to multiple low-risk encounters.

In this way you will at least know whether the contact persons had a high or low risk of infection.

What is the contact diary?

Just before the turn of the year brings an update Version 1.10 now a contact diary in the Corona warning app. The developers explain it in this post. There are also step-by-step instructions for using the new module.

In the contact diary you can voluntary write down where you were at what time and which people you met. The data will be saved on your smartphone and not automatically sent to authorities or app servers. The diary should serve as a reminder to inform the health department about possible Contact persons to call if you should be infected. It is up to you whether you give the office the details. All entries in the contact diary will be automatically deleted after 16 days.

Why can I enter my symptoms?

Another new option of the Corona warning app in the version dated October 19, 2020 is that people who tested positive can now voluntarily enter their symptoms in a kind of diary in the app. If you don't want that, you can simply ignore the function.

The background is that this can improve the app's risk calculation. The assumption: people with certain symptoms are more contagious to those around them than without these symptoms. If, for example, you got close to other people on days with these symptoms, this is included in the assessment of how risky the encounter was for these other people (along with a few other factors such as duration and distance during contact). However, other app users do not see what exactly was included in the calculation, including your symptoms.

What role do Google and Apple play in the Corona warning app?

Google and Apple are not providers of the Corona warning app. Nevertheless, they play an important role because they are the two major manufacturers of smartphone operating systems (Android and iOS). Google and Apple provide important technical functionalities on the smartphone so that the app can work properly.

In May 2020, Apple initially made the interfaces available for iPhones with the system version iOS 13 (through an update to version 13.5). In December 2020, the function was also available for iOS 12.5. Google provides the interface for several Android versions.

While Apple users had to update their operating system to version 13.5, Google relies on a solution via the app for the Google account that every Android user has on their smartphone. This means you are independent of smartphone manufacturers and also reach users who no longer receive updates for their operating system. If you Android you can find the new interface as follows:

  • Open the Settings.
  • Tap on Google or. Google settings.
  • The first menu item in the "Services" area should be Notification of possible contact with COVID-19 infected people stand.
  • If you tap the menu item, you can delete your random ID and deactivate contact notifications. However, this only works if a corresponding app, such as the Corona warning app that is currently in progress, has been installed.

Users of AppleDevices can update to iOS 13.5 at Settings, Generally, Software update download and install. After that you can find the function for the tracing app as follows:

  • Open the Settings.
  • Tap on privacy.
  • Tap on Bluetooth or Health (the names may differ depending on the iPhone model).
  • There should be the menu item COVID-19 contact log stand. If you tap it, you can turn on the interface. It is disabled by default. It cannot be activated until you have installed an authorized app on your iPhone or iPad.

IDs are not automatically created and used with the updates. This only works if the Corona warning app is also installed and you have to actively approve it.

The fact that the function "just appeared" on Android, without users having to do anything, provided the breeding ground for chain letters in messengers and social networks with false reports about espionage. In fact, the interface cannot work at all without an additionally installed app.

How error-prone is the determination of the relevant contacts?

This is difficult to assess, as Bluetooth technology is being used for the first time for the purpose of contact tracing and there are no reliable findings on this yet.

Since Bluetooth technology is used for completely new targets, it cannot be ruled out that both false-positive (contact was triggered, although there was actually none) and false-negative (relevant contact remains undetected) messages occur.

What is the difference between a tracing app and tracking apps?

The difference is not just in one letter. The essential component of a tracing warning app, such as the federal government's Corona warning app, is the use of Bluetooth technology. This only records the relevant "digital handshakes", i.e. whether a relevant contact has taken place at all. It is not recorded where these contacts took place. Location tracking, as would be possible via GPS or the cellular network, does not take place with the Corona warning app.