Imaging Features of COVID-19 Compared to SARS and MERS

Overview of COVID-19

COVID-19, caused by the novel coronavirus, is a highly contagious respiratory illness that originated in Wuhan City, China. This disease belongs to the same viral family as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).

Symptoms and Diagnosis

The respiratory manifestations of COVID-19 are akin to those observed in SARS and MERS, including fever, cough, malaise, and breathing difficulties. Researchers have examined imaging data from patients infected with SARS and MERS to identify common changes in chest images that may also present in COVID-19 cases. The findings of this radiological investigation were published in the American Journal of Roentgenology.

Importance of Chest Imaging

Chest imaging is crucial for diagnosing and tracking the progression of respiratory illnesses. In the context of SARS and MERS, chest images during both acute and chronic stages tend to be non-specific. Approximately 80% of SARS patients display abnormal chest imaging, often characterized by unilateral, focal disease with peripheral airspace opacity. Follow-up imaging typically reveals multifocal consolidation in one or both lungs. Similarly, CT scans reveal consolidation alongside patchy areas of ground-glass opacities.

For MERS patients, about 83% show abnormal chest imaging, primarily exhibiting multifocal airspace opacities in the lower lung regions on X-ray or CT scans. Long-term imaging follow-ups for SARS infections often reveal transient reticular opacities and air trapping, with fibrosis being rare. In contrast, MERS follow-ups may show similar transient opacities, with approximately one-third of patients developing fibrosis.

COVID-19 Imaging Characteristics

The imaging features of COVID-19 are also non-specific. Initial imaging reports from 40 out of 41 COVID-19 patients indicated bilateral lung involvement during the first CT scan, with non-ICU patients displaying a ground-glass pattern and ICU patients showing consolidation. It was confirmed that 86% of patients had both lungs affected, with 57% presenting multifocal ground-glass opacities and 29% exhibiting consolidation.

While imaging results for COVID-19 share similarities with those of SARS and MERS, a notable distinction is that COVID-19 typically affects both lungs, whereas SARS and MERS often present unilaterally. It is crucial to recognize that a normal early CT scan does not rule out an infection.

Expert Insights

Melina Hosseiny, one of the authors of the study, remarked, “Early evidence suggests that initial chest imaging will show abnormality in at least 85% of patients, with 75% of patients having bilateral lung involvement initially that most often manifests as subpleural and peripheral areas of ground-glass opacity and consolidation.” She also noted that “older age and progressive consolidation” may indicate a poorer prognosis overall.

Hosseiny et al. further stated, “To our knowledge, pleural effusion, cavitation, pulmonary nodules, and lymphadenopathy have not been reported in patients with COVID-19.”

References

1. Hosseiny, M., Kooraki, S., Gholamrezanezhad, A., Reddy, S. and Myers, L. (2020). Radiology Perspective of Coronavirus Disease 2019 (COVID-19): Lessons From Severe Acute Respiratory Syndrome and Middle East Respiratory Syndrome. American Journal of Roentgenology, pp. 1-5.
2. EurekAlert!. (2020). AJR: Novel coronavirus (COVID-19) imaging features overlap with SARS and MERS. [online] Available at: https://www.eurekalert.org/pub_releases/2020-02/arrs-anc022820.php [Accessed 3 Mar. 2020].
Image by Gerd Altmann from Pixabay.