The clinical spectrum of COVID-19: A population-based cohort study in Iceland

  1. Elias Eythorsson
  2. Dadi Helgason
  3. Ragnar Freyr Ingvarsson
  4. Helgi K Bjornsson
  5. Lovisa Bjork Olafsdottir
  6. Valgerdur Bjarnadottir
  7. Hrafnhildur Linnet Runolfsdottir
  8. Solveig Bjarnadottir
  9. Arnar Snaer Agustsson
  10. Kristin Oskarsdottir
  11. Hrafn Hliddal Thorvaldsson
  12. Gudrun Kristjansdottir
  13. Brynja Armannsdottir
  14. Agnar Bjarnason
  15. Birgir Johannsson
  16. Olafur Gudlaugsson
  17. Magnus Gottfredsson
  18. Martin I Sigurdsson
  19. Olafur S Indridason
  20. Runolfur Palsson
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Abstract

Background

Previous studies on the epidemiology and clinical characteristics of COVID-19 have generally been limited to hospitalized patients. The aim of this study was to describe the complete clinical spectrum of COVID-19, based on a nationwide cohort with extensive diagnostic testing and a rigorous contact tracing approach.

Methods

A population-based cohort study examining symptom progression using prospectively recorded data on all individuals with a positive test (RT-PCR) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who were enrolled in a telehealth monitoring service provided to all identified cases in Iceland. Symptoms were systematically monitored from diagnosis to recovery.

Results

From January 31 to April 30, 2020, a total of 45,105 individuals (12% of the Icelandic population) were tested for SARS-CoV-2, of whom 1797 were positive, yielding a population incidence of 5 per 1000 individuals. The most common presenting symptoms were myalgia (55%), headache (51%), and non-productive cough (49%). At the time of diagnosis, 5.3% of cases reported no symptoms and 3.1% remained asymptomatic during follow-up. In addition, 216 patients (13.8%) and 349 patients (22.3%) did not meet the case definition of the Centers for Disease Control and Prevention and the World Health Organization, respectively. The majority (67.5%) of patients had mild symptoms throughout the course of the disease.

Conclusion

In the setting of broad access to diagnostic testing, the majority of SARSCoV-2-positive patients were found to have mild symptoms. Fever and dyspnea were less common than previously reported. A substantial proportion of patients did not meet recommended case definitions at the time of diagnosis.

Key points

Question

What is the frequency and progression of various symptoms experienced by patients with COVID-19?

Findings

In this population-based cohort study that included all SARS-CoV-2-positive patients in Iceland, most patients (67.5%) had mild symptoms throughout their disease course. At the time of diagnosis, 5.3% were asymptomatic, of whom roughly half developed symptoms during follow-up. Common presenting symptoms included myalgia (55%), headache (51%), and non-productive cough (49%). At diagnosis, 13.8% and 22.3% did not meet the Centers for Disease Control and Prevention and World Health Organization case definitions for suspected COVID-19, respectively.

Meaning

In the setting of broad access to diagnostic testing, the majority of SARSCoV-2-positive patients were found to have mild symptoms and almost one-fifth did not meet published clinical criteria for RT-PCR testing.

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