From December 2019 to April 2020, we recruited all eligible hospitalized adults with respiratory infection to a prospective observational study at a tertiary care hospital in Finland. Influenza and SARS-CoV-2 infections were confirmed by RT-PCR. Follow-up lasted for 3 months from admission.
We included 61 patients, of whom 28 were COVID-19 and 33 influenza patients with median ages of 53 and 56 years. Majority of both COVID-19 and influenza patients were men (61% vs. 67%) and had at least one comorbidity (68% vs. 85%). Pulmonary diseases and current smoking were less common among COVID-19 than influenza patients (5 [18%] vs. 15 [45%], =.03 and 1 [4%] vs. 10 [30%], =.008). In chest X-ray at admission, ground-glass opacities (GGOs) and consolidations were more frequent among COVID-19 than influenza patients (19 [68%] and 7 [21%], <.001). Severe disease and intensive care unit (ICU) admission occurred more often among COVID-19 than influenza patients (26 [93%] vs. 19 [58%], =.003 and 8 [29%] vs. 2 [6%], =.034). COVID-19 patients were hospitalized longer than influenza patients (six days [IQR 4-21] vs. 3 [2-4], <.001).
Bilateral GGOs and consolidations in chest X-ray may help to differentiate COVID-19 from influenza. Hospitalized COVID-19 patients had more severe disease, required longer hospitalization and were admitted to ICU more often than influenza patients, which has important implications for public health policies.