The table below lists the more common respiratory pathogens:

Pathogen Associated condition
Respiratory syncytial virus Bronchiolitis
Parainfluenza virus Croup
Rhinovirus Common cold
Influenza virus Flu
Streptococcus pneumoniae The most common cause of community-acquired pneumonia
Haemophilus influenzae Community-acquired pneumonia
Most common cause of bronchiectasis exacerbations
Acute epiglottitis
Staphylococcus aureus Pneumonia, particularly following influenza
Mycoplasma pneumoniae Atypical pneumonia
Flu-like symptoms classically precede a dry cough. Complications include haemolytic anaemia and erythema multiforme
Legionella pneumophilia Atypical pneumonia
Classically spread by air-conditioning systems, causes dry cough. Lymphopenia, deranged liver function tests and hyponatraemia may be seen
Pneumocystis jiroveci Common cause of pneumonia in HIV patients. Typically patients have few chest signs and develop exertional dyspnoea
Mycobacterium tuberculosis Causes tuberculosis. A wide range of presentations from asymptomatic to disseminated disease are possible.
Cough, night sweats and weight loss may be seen

Rash in lower limbs ⇒ Mycoplasma

AC vent, water systems & Hyponatraemia ⇒ Legionella

Alcoholic ⇒ Klebsiella

Recent Flu ⇒ Staphylococcus

HIV ⇒ Pneumocystis