dcyphr | Influenza-associated pneumonia as reference to assess seriousness of coronavirus disease (COVID-19).


Understanding the severity of COVID-19 is crucial for proper healthcare. A simple approach to assessing disease seriousness is presented. The reference group consists of influenza patients with pneumonia from German hospitals. It was found that there were more deaths among COVID-19 patients without underlying conditions than in the reference group.  


The assessment of the seriousness of COVID-19 was generated by comparing well-described cases from hospitalized COVID-19 patients from Wuhan, Beijing, Shenzhen, Hubei and Zhejiang to a reference group consisting of inpatients diagnosed with influenza-associated pneumonia in several German Hospitals. Several parameters of seriousness associated with COVID-19 were compared, such as acute respiratory distress syndrome, ventilation, intensive care, and case fatality. Outcomes and risk factors for critically ill patients such as the reception of intensive care and ventilation were also compared. Differences in the different cohorts, such as age and gender ratios, were adjusted accordingly. 


Before discussing outcomes, it is important to note that the proportion of patients with co-morbidities was much smaller in the COVID-19 groups (20-51 percent) than in the pneumonia group (70-77 percent). Hypertension and diabetes were the most important chronic co-morbidities among both COVID-19 patients and pneumonia patients.

The proportion of patients in the ICU among the German pneumonia cohort was 20 percent. Three case series of COVID-19 produced proportions of ICU patients at 10 percent or lower, and two produced proportions of around 20 percent.

The median age of ICU patients for COVID-19 and influenza-associated pneumonia were 66 and 67 years respectively.

28 percent of COVID-19 patients treated on the ICU did not have any reported comorbidity, whereas only 16 percent of German ICU patients were without comorbidities.

Three COVID-19 case series found the proportion of COVID-19 inpatients who required ventilation was around 25 percent. German pneumonia patients had a much lower ventilation rate of 9 percent. This difference can be attributed to a high rate of acute respiratory distress syndrome (ARDS) among COVID-19 patients. ARDS is only observed in 1 percent of influenza-associated pneumonia patients.

The case fatality rate of the German pneumonia cohort hovered at around 6 percent. For case studies of COVID-19 in which the proportion of patients who were still hospitalized was 60 percent or below, the fatality rate ranged from 4 percent to 12 percent.

A different study by Yang et al. found that among 25 critically ill COVID-19 patients younger than 60 years, 12 died within 28 days after admission to the ICU, and that of 31 patients without chronic illnesses, 15 died.

In the German hospitals, of 462 pneumonia patients who were critically ill, 92 were younger than 60 years, of whom 12 (13 percent) died. In addition, 18 of the critically ill pneumonia patients were without chronic preconditions and four of them died. 


The proportion of severe cases requiring intensive care and the case fatality ratios were strikingly similar among COVID-19 and German pneumonia patients. Disease severity in younger adults below the age of 60 and in patients without chronic preconditions seems to be higher in COVID-19 patients than in pneumonia patients. Also, the rate of ARDS and use of ventilation was higher in COVID-19 patients than in influenza-associated pneumonia patients. 


Hospitals in regions across the globe that are becoming increasingly affected by COVID-19 must prepare for the high utilization of ventilation and intensive care resources, and this early preparation can promote positive outcomes. Also, although fatalities occur mostly among elderly people with chronic preconditions, COVID-19 infection still occurs in younger, healthy patients, and in a much higher rate than previously expected.