What causes pneumonia?

    Last Updated: October 25, 2023

    Many types of pathogens can cause pneumonia, such as:

    • Bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella pneumophila, and methicillin-resistant Staphylococcus aureus (MRSA)

    • Viruses: Human rhinovirus, influenza A or B, coronavirus, and respiratory syncytial virus (RSV)

    • Fungi: Pneumocystis jirovecii, Aspergillus spp., and Mucorales

    The most prevalent causative microbes vary geographically. Viruses account for the majority of cases in children (<5 years)[1], whereas bacteria and viruses account for most cases of pneumonia in adults. Fungal pneumonia is quite rare and usually occurs in people who are immunocompromised (e.g., cancer patients).[2]

    Pneumonia can also be caused by foods, liquids, or gastric contents inadvertently entering the lungs, a condition known as aspiration pneumonia.

    References

    1. ^Jain S, Williams DJ, Arnold SR, Ampofo K, Bramley AM, Reed C, Stockmann C, Anderson EJ, Grijalva CG, Self WH, Zhu Y, Patel A, Hymas W, Chappell JD, Kaufman RA, Kan JH, Dansie D, Lenny N, Hillyard DR, Haynes LM, Levine M, Lindstrom S, Winchell JM, Katz JM, Erdman D, Schneider E, Hicks LA, Wunderink RG, Edwards KM, Pavia AT, McCullers JA, Finelli L,Community-acquired pneumonia requiring hospitalization among U.S. children.N Engl J Med.(2015-Feb-26)
    2. ^Torres A, Cilloniz C, Niederman MS, Menéndez R, Chalmers JD, Wunderink RG, van der Poll TPneumonia.Nat Rev Dis Primers.(2021-Apr-08)