Development of Interstitial Lung Disease (ILD) in Patients With Severe SARS-CoV-2 Infection

COVID-19, the infectious disease caused by the novel coronavirus SARS-CoV-2, currently poses a global economic, social, political and medical challenge. The virus originated in December 2019 in Wuhan, China, and has spread rapidly around the world. Currently, European countries, including Austria, are severely affected. In January 2020, the World Health Organisation declared a "Public Health Event of International Concern" and since 11 March 2020 COVID-19 has been classified as a pandemic. Overall mortality rates vary widely, ranging from 0.5 to 7%. These highly depend on the stringency of the tests in a particular region and the age of the patients with higher mortality rates in older people. The majority of patients show only mild symptoms with fever and/or cough, and it is even believed that there is a significant proportion of untested asymptomatic carriers that can transmit the virus to other people. 26 to 33% of in-patients have been admitted to intensive care due to a severe lung disease. Of these, 2.5 to 10% required invasive mechanical ventilation and 15 to 22% of these patients died in hospital, indicating the potential risk to public health. As a result, the current global death toll from COVID-19 already exceeds 37,000 people on 31 March 2020.

In the SARS-CoV-1 outbreak of 2003, clinical course was characterized by fever, myalgia and other systemic symptoms, which generally improved after a few days, followed by a second phase with recurrence of fever, oxygen saturation and imaging progression of pneumonia, similar to that experienced by severely affected patients in the current pandemic. Importantly, a significant number of patients infected with SARS-CoV-1 suffered acute respiratory failure (ARDS) requiring invasive ventilatory support. The pulmonary pathology of fatal SARS cases was dominated by diffuse alveolar damage (DAD), epithelial cell proliferation, an increase in macrophages in the lung and extensive consolidation, but features of bronchiolitis obliterans and organizing pneumonia were also noted. In addition, survivors of severe SARS-CoV-1 infection showed significant functional and radiological changes in the lungs even 6 months after infection.

In the current SARS-CoV-2 pandemic, the most common computed tomographic changes in acute lung injury include bilateral and subpleural milk glass opacity, consolidation in lower lobes, or both. In the intermediate phase of the infection (4-14 days after the onset of symptoms) a so-called "crazy paving" may occur. The most prominent radiological changes occur around day 10, followed by gradual resolution, which begins two weeks after the onset of symptoms.

Given the phylogenetic relationship between SARS-CoV-1 and SARS-CoV-2, the similar clinical course in severe cases and overlapping CT patterns in the acute setting, persistent radiological and pulmonary functional changes in survivors are conceivable. It is also conceivable that a proportion of survivors will develop progressive ILD, either due to viral or ventilator-induced alveolar damage, or both.

Here, the investigators intend to investigate COVID-19 survivors through clinical examinations, functional lung examinations, HR-CT scans, and by determining the "immunofibrotic" pattern in peripheral mononuclear cells (PBMCs) 1, 3, and 6 months after discharge.