Principal(aux) agent(s) infectieux responsable(s) :
Nombreux virus : Adénovirus, Cytomégalovirus, Myxovirus influenzae
Virus parainfluenzae, Virus respiratoire syncytial ...
Bactéries :
Acinetobacter baumanii, Burkholderia cepacia, Chlamydia pneumoniae
Chlamydia psittaci, Chlamydia trachomatis, Coxiella burnetti
Enterobacter aerogenes, Enterobacter cloacae, Haemophilusinfluenzae
Klebsiella pneumoniae, Legionella pneumophila, Mycobacterium africanum
Mycobacterium bovis, Mycobacterium tuberculosis, Mycoplasma pneumoniae
Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus
Stenotrophomonas maltophilia, Streptococcus pneumoniae ...
Parasite : Pneumocystis carinii hominis
Champignon :
Cryptococcus neoformans, Coccidioïdes immitis, Histoplasma capsulatum