COVID-19 vs. Influenza: A Chest X-ray Comparison.

Introduction COVID-19 and influenza are primarily respiratory diseases, have similar symptoms with most patients developing mild to moderate illness, and show similar features on chest X-rays. We hypothesize that patients seeking treatments at the emergency department (ED) due to COVID-19 or influenza infection will have similar severity levels of features on chest X-rays, with most of them demonstrating normal to mildly abnormal chest X-ray findings.  Methods Chest X-ray images of 312 COVID-19 patients and 312 influenza patients were obtained from the teaching files of a general diagnostic radiologist. Images from each of these two groups were reviewed and classified. Based on the severity levels of lung abnormalities, each image was categorized into one of four categories: normal, mildly abnormal, moderately abnormal, or severely abnormal. The total number of images in each category within each disease group was counted, and the percentage was calculated compared to the total number of images analyzed in that group. Results from both groups were then compared. Results The severity levels of chest X-ray abnormalities were similar between the COVID-19 group and the COVID-negative influenza group at the time of ED visits, with most images being normal or mildly abnormal. The percentages of the images categorized as normal, mildly abnormal, moderately abnormal, and severely abnormal in the COVID-19 group and the influenza group were 38-39%, 28-29%, 22-21%, and 12-11%, respectively. Conclusion Our findings suggest that in the ED setting, no distinction can be made between COVID-19 and Influenza infections if based just on chest X-rays.