Abstract
The presence of secondary bacterial infection is important in viral infectious disease. Influenza is known to become more severe with secondary bacterial pneumonia in particular when the Streptococcus pneumoniae and Haemophilus influenzae are co-infected, but with COVID-19, there are thought to be few concomitant bacterial infections. However, mortality in COVID-19 patients also increases with secondary bacterial infections, mainly Staphylococcus aureus such as MRSA and Gram-negative bacilli, and vigilance is needed. Consequently, there is a rising trend in prescriptions for antibiotics, but more appropriate diagnosis and antimicrobial stewardship are needed to suppress antimicrobial resistance, and vaccination will be the key strategy to prevent the severe viral infections related with secondary bacterial infection.