Bacterial co-infections increase the severity of respiratory viral infections and were frequent causes of mortality in influenza pandemics, but have not been well characterized in patients with coronavirus disease 2019 (COVID-19). The aim of this review was to identify the frequency and microbial etiologies of bacterial co-infections that are present upon admission to the hospital and that occur during hospitalization for COVID-19. We found that bacterial co-infections were present in <4% of patients upon admission and the yield of routine diagnostic tests for pneumonia was low. When bacterial co-infections did occur,
Staphylococcus aureus
,
Streptococcus pneumoniae,
and
Haemophilus influenzae
were the most common pathogens and atypical bacteria were rare. Although uncommon upon admission, bacterial infections frequently occurred in patients with prolonged hospitalization and
Pseudomonas aeruginosa
,
Klebsiella
spp., and
S. aureus
were common pathogens. Antibacterial therapy and diagnostic testing for bacterial infections are unnecessary upon admission in most patients hospitalized with COVID-19, but clinicians should be vigilant for nosocomial bacterial infections.