Introduction: Respiratory viruses can occur with endemics and pandemics worldwide, which cause high morbidity and mortality in solid organ transplant (SOT) recipients. In this study we aim to evaluate the differences between two respiratory viruses (Influenza and SARS-CoV-2) in SOT recipients.

Method: In the study was compared SOT patients diagnosed with Influenza by PCR test between 2018-2020 and diagnosed with COVID-19 by PCR test between 2020-2022. Clinical characteristics and clinical course of two respiratory viruses were evaluated. The data of the patients were obtained from the hospital information management system and was analyzed with the SPSS.25 programme.

Results: There were a total of 95 patients. Fifty-three patients were diagnosed with COVID-19 and 42 patients diagnosed with Influenza. The median age was 49 (range 20-72) years for patients with COVID-19 and 47.5 (range 18-80) years for patients with Influenza. Male gender was higher than females in all cohort (71.6%). At admission 49.1% of patients with COVID-19 reported fever, 39.6% reported cough, 9.4% reported sore throat. The 71.4% of patients with Influenza reported fever, 57.1% reported cough and 31% reported sore throat. Fever and sore throat was significantly higher in Influenza group (p: 0.028, 0.008 respectively). Thorax computed tomography (CT) was performed 84.9% (p<0.001) patients in COVID-19 group, and 86.7% of them had any sign in CT (p:0.003). While there was no significant difference in hospitalization between the groups, the need for intensive care support (32.1%) and mechanical ventilation (26.4%) was significantly higher in the COVID-19 group (p: 0.009, 0.005 respectively). Despite the fact that there was no significant difference, the duration of hospitalization and intensive care unit was longer in the COVID-19 group. The 90-days mortality rate was significantly higher in the COVID-19 group (13/53 (24.5%), p: 0.009).

Conclusion: Although solid organ transplantation can save lives, there is an increased risk of infection. Respiratory viral infections are among the most common infections, causing significant morbidity and mortality. Based on our results, COVID-19 have devastating effects as pulmonary involvement, ICU support, and higher mortality in SOT recipients than Influenza.  Due to the ongoing pandemic and changing SARS-CoV-2 variants and effects, SOT patients should not neglect non-pharmaceutical interventions and their primary or booster vaccines.