SARS-CoV-2-related pneumonia cases in pneumonia picture in Russia in March-May 2020: Secondary bacterial pneumonia and viral co-infections

Background: We are communicating the results of investigating statistics on SARS-CoV-2-related pneumonias in Russia: percentage, mortality, cases with other viral agents, cases accompanied by secondary bacterial pneumonias, age breakdown, clinical course and outcome. Methods: We studied two sampling sets (Set 1 and Set 2). Set 1 consisted of results of testing 3382 assays of out-patients and hospital patients (5-88 years old) with community-acquired and hospital-acquired pneumonia of yet undetermined aetiology. Set 2 contained results of 1204 assays of hospital patients (12-94 years old) with pneumonia and COVID-19 already diagnosed by molecular biological techniques in test laboratories. The results were collected in twelve Russian cities/provinces in time range 2 March - 5 May 2020. Assays were analysed for 10 bacterial, 15 viral, 2 fungal and 2 parasitic aetiological agents. Results: In Set 1, 4.35% of total pneumonia cases were related to SARS-CoV-2, with substantially larger proportion (18.75%) of deaths of pneumonia with COVID-19 diagnosed. However, studying Set 2, we revealed that 52.82% patients in it were also positive for different typical and atypical aetiological agents usually causing pneumonia. 433 COVID-19 patients (35.96%) were tested positive for various bacterial aetiological agents, with Streptococcus pneumoniae, Staphylococcus aureus and Haemophilus influenzae infections accounting for the majority of secondary pneumonia cases. Conclusions: SARS-CoV-2, a low-pathogenic virus itself, becomes exceptionally dangerous if secondary bacterial pneumonia attacks a COVID-19 patient as a complication. An essential part of the severest complications and mortality associated with COVID-19 in Russia in March-May 2020, may be attributed to secondary bacterial pneumonia and to a much less extent viral co-infections. The problem of hospital-acquired bacterial infection is exceptionally urgent in treating SARS-CoV-2 patients. The risk of secondary bacterial pneumonia and its further complications, should be given very serious attention in combating SARS-CoV-2