Description and analysis of representative COVID-19 cases-A retrospective cohort study

PLoS One. 2021 Jul 30;16(7):e0255513. doi: 10.1371/journal.pone.0255513. eCollection 2021.


Background: Most data on COVID-19 was collected in hospitalized cases. Much less is known about the spectrum of disease in entire populations. In this study, we examine a representative cohort of primarily symptomatic cases in an administrative district in Southern Germany.

Methods: We contacted all confirmed SARS-CoV-2 cases in the administrative district. Consenting participants answered a retrospective survey either via a telephone, electronically or via mail. Clinical and sociodemographic features were compared between hospitalized and non-hospitalized patients. Additionally, we assessed potential risk factors for hospitalization and time to hospitalization in a series of regression models.

Results: We included 897 participants in our study, 69% out of 1,305 total cases in the district with a mean age of 47 years (range 2-97), 51% of which were female and 47% had a pre-existing illness. The percentage of asymptomatic, mild, moderate (leading to hospital admission) and critical illness (requiring mechanical ventilation) was 54 patients (6%), 713 (79%), 97 (11%) and 16 (2%), respectively. Seventeen patients (2%) died. The most prevalent symptoms were fatigue (65%), cough (62%) and dysgeusia (60%). The risk factors for hospitalization included older age (OR 1.05 per year increase; 95% CI 1.04-1.07) preexisting lung conditions (OR 3.09; 95% CI 1.62-5.88). Female sex was a protective factor (OR 0.51; 95% CI 0.33-0.77).

Conclusion: This representative analysis of primarily symptomatic COVID-19 cases confirms age, male sex and preexisting lung conditions but not cardiovascular disease as risk factors for severe illness. Almost 80% of infection take a mild course, whereas 13% of patients suffer moderate to severe illness.

Trial registration: German Clinical Trials Register, DRKS00022926. URL:

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • COVID-19* / mortality
  • COVID-19* / pathology
  • COVID-19* / therapy
  • Child
  • Child, Preschool
  • Female
  • Hospitalization*
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Risk Factors
  • SARS-CoV-2*
  • Severity of Illness Index
  • Sex Factors

Grants and funding

This work was supported by internal COVID funds of the Heidelberg University Hospital.