Estimating the COVID-19 Prevalence in Spain With Indirect Reporting via Open Surveys

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found at: https://github.com/GCGImdea/coronasurveys.
During the initial phases of the COVID-19 pandemic, accurate tracking has proven unfeasible. Initial estimation methods pointed toward case numbers that were much higher than officially reported. In the CoronaSurveys project, we have been addressing this issue using open online surveys with indirect reporting. We compare our estimates with the results of a serology study for Spain, obtaining high correlations (R squared 0.89). In our view, these results strongly support the idea of using open surveys with indirect reporting as a method to broadly sense the progress of a pandemic.
At the time of writing this article, Corona Surveys has received no public funding. Social networks surveys have been partially funded via donations through our website. CoronaSurveys received an award from the UMD/CMU COVID-19 Symptom Data Challenge.