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48 hours of hacking in the service of fighting Corona. Together with 44000 participants nationwide, we spent the weekend developing and working on projects for #wirvsvirus, the German government's hackathon on Corona.


From their homes, students, graduates, staff and professors of the HfG worked intensively for two days to trace chains of infection.

Gretel helps to identify and break infection chains: Movement and contact data can be collected from a digital app and an analogue scanning stations. From this, appropriate recommendations for action can be made if "risk contacts" have occurred.

There is a special focus on the involvement of the non-digital risk group. Via The analogue component of the system can also register and classify them.


We wanted to identify chains of infection so that we could interrupt them as quickly as possible. interrupt them as quickly as possible. To do this, it is important to have a good overview of the movement and contact behaviour over at least the last 14 days. In this way, those affected, infected persons can be identified at an early stage and the appropriate measures can be initiated.


Gretel collects, collates and accumulates movement and contact data from various sources - partly automatically, partly manually supplemented. This makes it possible to trace who was in contact with whom, when and in what context, so that infection chains can be quickly identified and interrupted at an early stage.

A digital app is supplemented by analogue ID cards (in the usual cheque card format) and hardware that also allows the participation of non-digitally networked persons. Shops and public institutions will be provided with DIY kits that allow the setting up of scanning stations. Here, participants can be given an analogue ID card which they can scan when entering and leaving the building, means of transport, etc., in order to make their data available. to make their data available.

All those who provide data can be informed promptly about risks of infection. infection. Different statuses - from healthy to infected to cured - are determined. infected to cured - which allow an assessment and information about the overall situation.

Gretel thus provides the user with practical measures for the next few days, to be able to react appropriately and quickly to the current situation.


Early on in the process we created click-dummies of the app and Paper prototypes of the hardware components, to simulate and test our concept.

In addition, we started with the development of the frontends (Mobile for end-users, and tablet for stationary scans) and built a backend based on the AWS infrastructure and connected a backend to it. The accumulating data is stored anonymously in the cloud in Amazon DynamoDB, which also scales well for large numbers of users.

There is a functional part of the mobile app based on reactnative, as well as a functional web application for the "analogue" tablet tablet solution based on vue.js. The system is quickly connected via REST APIs to other systems other systems such as health authorities.

The mobile app collects position and "encounter data" using WLAN and Bluetooth scans, GPS and also manual barcode scans/checkins, for example when app users known in person meet. This data is transmitted to the cloud backend and evaluated for potential encounters with infected persons. The app or tablet station can then warn users if they develop symptoms and encourage them to contact a doctor or limit their contacts with other people as a precautionary measure. Planned features include data analysis in the backend AWS services for "matching" and and extended contact score calculation.

build with…

Pen and Paper, Miro, Figma, Illustrator, ProCreate, Photoshop, After Effects, Premiere, draw.io, Vue.js, Expo, Visual Studio Code, React, Node.js, AWS Amplify, Rest:API, API Gateway, Amazon Lambda, DynamoDB


For a better perception of our Gretel stations, they should ideally be placed directly at the entrance or exit. For this purpose, the devices should be specially configurable as entrance or exit devices. The scanner used in supermarkets for the payback card could also take over the task of the exit device.

In the course of this, the customer should be asked directly by the checkout staff if they would like to sign out with their Gretel card.

We also see a lot of potential in the application for other infectious diseases.


We are very proud of what we have achieved within 48 hours. At the beginning there was nothing except for some ideas. We managed the available time optimally. The team and the spirit of the last days was overwhelming.

We gained a lot of experience about remote work. Although we were scattered all over Germany, we worked together on the project for almost 48h. With tools like Miro for ideation or Fimga for design, we were able to work together on content and designs.

Project Info

Carmen Menzel
Dominik Fink
Dominik Witzke
Felix Arnold
Felix Häberle
Florian Geiselhart
Julia Wittich
Lisa Amanm
Luca Stetter
Mario Rieker
Marius Schnabel
Max Walter
Michael Schuster
Sven Löchner
Tobias Schmücker
Vanessa Stöckel