To better understand and more quickly identify how coronavirus is spreading among the Swiss population, the team led by Gunnar Rätsch, Professor for Biomedical Informatics at ETH Zurich and University Hospital Zurich, developed the COVID-19 symptom survey (see ETH News, 31 March 2020 ). Anyone living in Switzerland can fill out the questionnaire on the website in just a few minutes.

Independently of this project, a small group of students and companies had already been working with the canton of Bern’s former cantonal doctor, Jan von Overbeck, to set up a similar survey platform. The two platforms and their questionnaires have now been combined to offer a single Covid-19 symptom tracker, which was put on the website www.covidtracker.ch on Sunday.

One goal of the survey is to quickly develop a meaningful map of potential hazard clusters in order to show where there are particularly high numbers of COVID-19 cases and how the pandemic is distributed regionally. This would allow very targeted containment measures and identification of a second wave of infections at an early stage.

A current map is available at: www.covidtracker.ch/map . The combined data from the two sources currently comprises about 225,000 responses – primarily from the Zurich, Bern and Lake Geneva regions.

“For us researchers, combining the data gives the advantage that coverage is now broader, and the questionnaire is more meaningful and interactive,” says Rätsch. Respondents are asked whether they have experienced typical COVID-19 symptoms now or in the past, if they have been tested for coronavirus, how they would describe their state of health along with any relevant pre-existing conditions, and whether they go to work regularly, live in self-isolation or work in healthcare. Their gender, age, size of household and postal code are also collected.

Anonymised data for early detection

The data collected with the Covid-19 symptom tracker is anonymised. The survey is designed so that it can be completed multiple times by assigning each person a code, which the system uses to aggregate the appropriate data. At the same time, the data cannot be traced back to any specific individual. However, the data can still be used for various types of analyses.

One of the researchers’ objectives is to develop new data analysis methods and models of the epidemic using real-time data. Since the questionnaires are completed over an extended period, researchers also obtain data on how a respondent’s state of health changes over time.

Rätsch and his team are developing algorithms that will one day contribute to the early detection of COVID-19; for example, by linking a positive coronavirus test to symptoms in the days prior, thus determining whether and when the symptoms actually reflect the respiratory infection.

In order to help the authorities curb the coronavirus epidemic, ETH Zurich and the canton of Bern have formed a consortium as part of the project to combine the two platforms. It includes representatives from ETH Zurich and the canton of Bern’s health, social and integration directorate (GSI). The consortium has already started its work and is pooling all existing data records.

As part of the collaboration, Rätsch’s team is responsible for research. The scientific part of the joint project is called “Tracking the Dynamics of COVID-19”.

Another goal beyond this partnership is to coordinate with similar projects and combine collected data – for example, the creators of covidtracker.ch are coordinating with the app-based initiative “ Corona Science ” launched by Bern University of Applied Sciences to complement each other’s data and help fight the pandemic.