Epidemiological Observations on the Association Between Anosmia and COVID-19 Infection: Analysis of Data From a Self-Assessment Web Application

J Med Internet Res. 2020 Jun 11;22(6):e19855. doi: 10.2196/19855.


Background: We developed a self-assessment and participatory surveillance web application for coronavirus disease (COVID-19), which was launched in France in March 2020.

Objective: Our objective was to determine if self-reported symptoms could help monitor the dynamics of the COVID-19 outbreak in France.

Methods: Users were asked questions about underlying conditions, sociodemographic status, zip code, and COVID-19 symptoms. Depending on the symptoms reported and the presence of coexisting disorders, users were told to either stay at home, contact a general practitioner (GP), or call an emergency phone number. Data regarding COVID-19-related hospitalizations were retrieved from the Ministry of Health.

Results: As of March 29, 2020, the application was opened 4,126,789 times; 3,799,535 electronic questionnaires were filled out; and 2,477,174 users had at least one symptom. In total, 34.8% (n=1,322,361) reported no symptoms. The remaining users were directed to self-monitoring (n=858,878, 22.6%), GP visit or teleconsultation (n=1,033,922, 27.2%), or an emergency phone call (n=584,374, 15.4%). Emergency warning signs were reported by 39.1% of participants with anosmia, a loss of the sense of smell (n=127,586) versus 22.7% of participants without anosmia (n=1,597,289). Anosmia and fever and/or cough were correlated with hospitalizations for COVID-19 (Spearman correlation coefficients=0.87 and 0.82, respectively; P<.001 for both).

Conclusions: This study suggests that anosmia may be strongly associated with COVID-19 and its severity. Despite a lack of medical assessment and virological confirmation, self-checking application data could be a relevant tool to monitor outbreak trends.

Trial registration: ClinicalTrials.gov NCT04331171; https://clinicaltrials.gov/ct2/show/NCT04331171.

Keywords: COVID-19; anosmia; epidemiological surveillance; epidemiology; outbreak; self-assessment; surveillance; symptoms; web application.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Betacoronavirus / pathogenicity*
  • COVID-19
  • Coronavirus Infections / epidemiology*
  • Coronavirus Infections / virology*
  • Disease Outbreaks
  • France / epidemiology
  • Humans
  • Middle Aged
  • Olfaction Disorders / epidemiology*
  • Olfaction Disorders / virology*
  • Pandemics
  • Pneumonia, Viral / epidemiology*
  • Pneumonia, Viral / virology*
  • SARS-CoV-2
  • Self-Assessment*
  • Surveys and Questionnaires*
  • Young Adult

Associated data

  • ClinicalTrials.gov/NCT04331171