Etiology of Pneumonia

Viral Causes

• RSV
• Influenza virus
• Parainfluenza virus
• Adenovirus

Bacterial Causes According to Age

Age Group	Common Organisms
First 2 months	Klebsiella, E. coli, pneumococci, staphylococci
3 months–3 years	Pneumococci, H. influenzae, staphylococci
>3 years	Pneumococci, staphylococci
Adolescents	Mycoplasma, Chlamydia

Opportunistic Organisms

• Pneumocystis jirovecii
• Histoplasma