Clinical spectrum of coronavirus disease 2019 in Iceland: population based cohort study

Abstract

Objective: To characterise the symptoms of coronavirus disease 2019 (covid-19).

Design: Population based cohort study.

Setting: Iceland.

Participants: All individuals who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by reverse transcription polymerase chain reaction (RT-PCR) between 17 March and 30 April 2020. Cases were identified by three testing strategies: targeted testing guided by clinical suspicion, open invitation population screening based on self referral, and random population screening. All identified cases were enrolled in a telehealth monitoring service, and symptoms were systematically monitored from diagnosis to recovery.

Main outcome measures: Occurrence of one or more of 19 predefined symptoms during follow-up.

Results: Among 1564 people positive for SARS-CoV-2, the most common presenting symptoms were myalgia (55%), headache (51%), and non-productive cough (49%). At the time of diagnosis, 83 (5.3%) individuals reported no symptoms, of whom 49 (59%) remained asymptomatic during follow-up. At diagnosis, 216 (14%) and 349 (22%) people did not meet the case definition of the Centers for Disease Control and Prevention and the World Health Organization, respectively. Most (67%) of the SARS-CoV-2-positive patients had mild symptoms throughout the course of their disease.

Conclusion: In the setting of broad access to RT-PCR testing, most SARS-CoV-2-positive people were found to have mild symptoms. Fever and dyspnoea were less common than previously reported. A substantial proportion of SARS-CoV-2-positive people did not meet recommended case definitions at the time of diagnosis.

Fig 1

Flowchart describing the derivation of the study cohort

Fig 2

Changes in severity of symptoms from onset to end of follow-up among SARS-CoV-2-positive individuals. The category “not yet diagnosed” comprises people yet to be enrolled in telehealth monitoring, and whose clinical severity had therefore not been evaluated. The severity of symptoms was categorised as low (mild and improving symptoms), moderate (mild dyspnoea, cough, or fever for less than 5 days), or high (worsening dyspnoea, worsening cough, high or persistent fever for 5 days or longer, or lethargy). The top panel includes all SARS-CoV-2-positive people. The other panels show people categorised by age; 0-9, 10-19, 20-39, 40-64, and ≥65 years

Fig 3

Cumulative incidence and proportion of SARS-CoV-2-positive individuals who experienced cough, dyspnoea, fever, and gastrointestinal symptoms by days from symptom onset. The parametric cure-mixture estimate of the cumulative incidence is illustrated in the upper panel with the 95% confidence interval shown as a shaded area. The lower panel depicts the logistic regression estimate of the proportion of infected individuals who experience each symptom by day (95% confidence intervals shown as a shaded area)