Purpose: To differentiate between respiratory infections caused by SARS-CoV-2 and other respiratory pathogens during the COVID-19 outbreak in Wuhan, we simultaneously tested for SARS-CoV-2 and pathogens associated with CAP to determine the incidence and impact of respiratory coinfections in COVID-19 patients.
Patients and Methods: We included 250 patients who were diagnosed with COVID-19. RT-PCR was used to detect influenza A, influenza B and respiratory syncytial viruses. Chemiluminescence immunoassays were used to detect IgM antibodies for adenovirus, Chlamydia pneumoniae  and Mycoplasma pneumoniae  in the serum of patients. Based on these results, we divided the patients into two groups, the simple SARS-CoV-2-infected group and the coinfected SARS-COV-2 group. Coinfected patients were then further categorized as having a coinfection of viral pathogen (CoIV) or coinfection of atypical bacterial pathogen (CoIaB).
Results: No statistically significant differences were found in age, gender, the time taken to return negative SARS-CoV-2 nucleic acid test results, length of hospital stays, and mortality between the simple SARS-CoV-2 infection group and the coinfection group. Of the 250 hospitalized COVID-19 patients, 39 (15.6%) tested positive for at least one respiratory pathogen in addition to SARS-CoV-2. A third of these pathogens were detected as early as the 1st week after symptom onset and another third were identified after more than three weeks. The most detected CAP pathogen was C. pneumoniae  (5.2%), followed by the respiratory syncytial virus (4.8%), M. pneumoniae  (4.4%) and adenovirus (2.8%). Patients coinfected with viral pathogens (CoIV) (n=18) had longer hospital stays when compared to patients coinfected with atypical bacterial pathogens (CoIaB) (n=21). Except for one fatality, the remaining 38 coinfected patients all recovered with favourable outcomes.
Conclusion: Coinfections in COVID-19 patients are common. The coinfecting pathogens can be detected at variable intervals during COVID-19 disease course and remain an important consideration in targeted treatment strategies for COVID-19 patients.
Keywords: SARS-CoV-2, COVID-19, viral coinfection, atypical bacterial coinfection