Influenza
URI
Pneumonia
Sinusitis
Toxic exposure
Pyelonephritis
Bronchitis
Coronavirus
MERS-CoV<unk> -CoV
2019-nCoV (COVID-19)
MERS-CoV<unk> -CoV
2019-nCoV (COVID-19)
URI (rhinitis, sinusitis, pertussis)
LRI (bronchitis, pneumonia)
Influenza
Allergy
Asthma
Environmental irritants
Transient airway hyperresponsiveness
Foreign body<unk> 
Postinfectious; pertussis
Smoking and/or chronic bronchitis
Postnasal discharge
Asthma
GERD
ACEI/ARB
CHF
Lung cancer or intrathoracic mass
Emphysema
Interstitial lung disease
Psychiatric
Gram-positive
Streptococcus pneumoniae
Staphylococcus aureus
Gram-negative
Haemophilus influenzae
Klebsiella pneumoniae
Escherichia coli
Pseudomonas aeruginosa 
Moraxella catarrhalis
Atypical pneumonia
Chlamydophila pneumoniae 
Chlamydophila psittaci
Mycoplasma pneumoniae
Coxiella burnetti 
Legionella pneumophila
Streptococcus pneumoniae
Staphylococcus aureus
Haemophilus influenzae
Klebsiella pneumoniae
Escherichia coli
Pseudomonas aeruginosa 
Moraxella catarrhalis
Chlamydophila pneumoniae 
Chlamydophila psittaci
Mycoplasma pneumoniae
Coxiella burnetti 
Legionella pneumophila
Common
Influenza<unk>  syncytial virus
Parainfluenza
Rarer
Adenovirus
Metapneumovirus<unk>  <unk> 
Middle east<unk>  syndrome coronavirus (MERS)
2019-nCoV (COVID-19)
Cause other diseases, but sometimes cause pneumonia
Herpes simplex virus
Varicella-zoster (VZV)
Measles
Rubella
Cytomegalovirus
Smallpox
Dengue
Influenza<unk>  syncytial virus
Parainfluenza
Adenovirus
Metapneumovirus<unk>  <unk> 
Middle east<unk>  syndrome coronavirus (MERS)
2019-nCoV (COVID-19)
Herpes simplex virus
Varicella-zoster (VZV)
Measles
Rubella
Cytomegalovirus
Smallpox
Dengue
Histoplasmosis
Coccidioidomycosis
Blastomycosis
Pneumocystis jirovecii pneumonia (PCP)
Sporotrichosis
Cryptococcosis
Aspergillosis
Candidiasis
Ascariasis
Schistosomiasis
Toxoplasma gondii
Severe acute respiratory syndrome
Influenza
CMV pneumonia
URI
Acute respiratory distress syndrome
Pneumonia
Ventilator associated pneumonia
Sinusitis