| Estimated frequency, percent | Examples | |
| Common bacterial pathogens | 15 | Group A streptococci |
| Group C streptococci | ||
| Group G streptococci | ||
| Less common bacterial pathogens | <5 | Chlamydophila pneumoniae (TWAR) |
| Mycoplasma pneumoniae | ||
| Arcanobacterium haemolyticum | ||
| Corynebactrium diphtheriae | ||
| Fusobacterium necrophorum | ||
| Neisseria gonorrheae | ||
| Treponema pallidum | ||
| Francisella tularensis | ||
| Viruses | 50 | Rhinovirus |
| Adenovirus | ||
| Influenza A and B | ||
| Parainfluenza | ||
| Coxsackievirus | ||
| Coronavirus | ||
| Echovirus | ||
| Herpes simplex virus | ||
| Epstein Barr virus | ||
| Human immunodeficiency virus | ||
| Cytomegalovirus | ||
| Respiratory syncytial virus | ||
| Metapneumovirus | ||
| No pathogen isolated | 30 |
