Disease Severity in Patients with Simultaneous Influenza and Bacterial Pneumonia

Objective To determine the differences in the clinical features of bacterial pneumonia patients between patients co-infected with influenza virus or not co-infected. Methods Fifteen adult patients with bacterial pneumonia (7 men and 8 women) who also tested positive for influenza virus antigen were compared with those with bacterial pneumonia alone (n=28). Results Complications with chronic lung diseases were more frequently found in bacterial pneumonia patients with influenza virus infection, compared with those who had bacteria pneumonia alone. Statistical differences were also found in body temperature, and heart rates between the two groups. CRP levels, chest Xray infiltrates and the severity of pneumonia, as determined using the criteria of the Japan Respiratory Society (JRS) and/or the Infectious Diseases Society of America (IDSA), were also significantly worse in patients of bacterial pneumonia infected with influenza virus, than in those who had bacterial pneumonia alone. Conclusions The severity of pneumonia in patients co-infected with influenza virus and bacteria was significantly higher than in those infected with bacteria alone. These data suggested that the influenza virus infection enhanced the bacterial pneumonia. Further study of the pathogenesis of the synergic interaction between influenza virus and bacteria is warranted.