Comparing COVID-19 and Influenza Presentation and Trajectory

Abstract

Background: COVID-19 is a newly recognized illness with a predominantly respiratory presentation. It is important to characterize the differences in disease presentation and trajectory between COVID-19 patients and other patients with common respiratory illnesses. These differences can enhance knowledge of pathogenesis and help in guiding treatment. Methods: Data from electronic medical records were obtained from individuals admitted with respiratory illnesses to Rambam Health Care Campus, Haifa, Israel, between October 1st, 2014 and October 1st, 2020. Four groups of patients were defined: COVID-19 (693), influenza (1,612), severe acute respiratory infection (SARI) (2,292), and Others (4,054). The variable analyzed include demographics (7), vital signs (8), lab tests (38), and comorbidities (15) from a total of 8,651 hospitalized adult patients. Statistical analysis was performed on biomarkers measured at admission and for their disease trajectory in the first 48 h of hospitalization, and on comorobidity prevalence. Results: COVID-19 patients were overall younger in age and had higher body mass index, compared to influenza and SARI. Comorbidity burden was lower in the COVID-19 group compared to influenza and SARI. Severely- and moderately-ill COVID-19 patients older than 65 years of age suffered higher rate of in-hospital mortality compared to hospitalized influenza patients. At admission, white blood cells and neutrophils were lower among COVID-19 patients compared to influenza and SARI patients, while pulse rate and lymphoctye percentage were higher. Trajectories of variables during the first 2 days of hospitalization revealed that white blood count, neutrophils percentage and glucose in blood increased among COVID-19 patients, while decreasing among other patients. Conclusions: The intrinsic virulence of COVID-19 appeared higher than influenza. In addition, several critical functions, such as immune response, coagulation, heart and respiratory function, and metabolism were uniquely affected by COVID-19.

Keywords: COVID-19; SARI; biomarkers; disease trajectory; influenza.

Figure 1

Cohort selection and criteria for exclusion. Data from a total of 9,670 admitted cases were extracted from the Rambam Health Care Campus electronic medical records system.

Figure 2

Comorbidity prevalence rates among study patients at admission. Moderate to severe cases were considered for COVID-19 patients. For all disease types but dementia, rates were lower among COVID-19 patients compared to other patients. The differences between disease groups were all statistically significant except for diabetes.

Figure 3

Heatmap of admission median standardized scores of (A) vital signs and (B) lab tests in COVID-19, influenza A/B, SARI and Others. All variables are introduced on the same scale, relative to the variable overall median. The standardized scores is positive if the group median is greater than the overall median (orange-red) and negative otherwise (purple-blue). Hierarchical clustering on the left points to groups with similar pattern across diseases.

Figure 4

Comparing trends across time—ranks means vs. time intervals. Blood pressure and pulse were decreasing more slowly during 6–48 h after admission among COVID-19 patients compared to influenza and SARI patients. Glucose and measures related to white blood cells (white blood count, lymphocytes, and neutrophils) among COVID-19 patients showed distinct trajectories, with respect to other patients.

Figure 5

Volcano plot of pairwise post hoc analysis of patients trajectory of COVID-19, influenza, SARI, and others for each lab tests. The level of significance is shown vs. the effect size, namely the slope difference (x—COVID-19). The most highly significant result was for average blood pressure, as seen at the left window, which refers to all influenza-COVID-19 comparisons, and at the right window, which refers to all SARI-COVID-19 comparisons. Trends for WBC, glucose, and diastolic blood pressure for COVID-19 patients were found to be different from both influenza and SARI.