Pneumonia
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Direct answer
Pneumonia is an acute bacterial infection of the lungs in which Streptococcus pneumoniae or Haemophilus influenzae colonises the alveoli. The alveoli and small bronchioles fill with fluid and mucus, so gas exchange is impaired and the patient suffers fever, chills and a cough, often with bloody sputum and breathlessness. The disease spreads from infected persons through droplets and aerosols released on coughing or sneezing, and also by sharing glasses and utensils.
What you must remember
- Causative organisms: Streptococcus pneumoniae and Haemophilus influenzae — the two bacteria NCERT names as agents of pneumonia.
- Site of infection: the alveoli of the lungs; in a severe infection the alveoli and bronchioles accumulate fluid and mucus, choking ventilation.
- Symptoms: fever, chills, cough productive of rusty or bloody sputum, headache and breathlessness in advanced disease.
- Transmission: inhaling droplets or aerosols expelled by patients, and using contaminated articles such as shared glasses and utensils.
- Portal: the respiratory tract, classifying pneumonia among the air-borne bacterial diseases along with typhoid's contrast as a water-borne infection.
- Vulnerable groups: the elderly, the very young, smokers, and people with weak immunity or co-existing lung disease suffer more severe illness per general medical observation.
- Prevention: avoiding close exposure to coughing patients, not sharing personal articles, hand hygiene, and timely medical care, since the disease is treatable with antibiotics prescribed by a physician.
Common confusion
Pneumonia and the common cold are both respiratory infections, but pneumonia is bacterial, lodges deep in the alveoli and produces fluid-filled lungs with bloody sputum, whereas the rhinovirus of the common cold infects only the nose and upper passages and never the lungs. Students also confuse the two pneumonia bacteria with the virus Haemophilus influenzae's misleading name suggests — despite "influenzae", it is a bacterium.
Exam-focused takeaway
NEET-UG tests pneumonia as an air-borne bacterial disease of the alveoli, asking for the two causative bacteria, the fluid accumulation that explains breathlessness, and the transmission modes of droplets and shared utensils. Match-the-following tables pair disease, pathogen and affected organ, and statement questions test that pneumonia, unlike the common cold, is alveolar rather than upper-respiratory.
Frequently asked questions
Which bacteria cause pneumonia?
Streptococcus pneumoniae and Haemophilus influenzae, both of which infect the alveoli of the lungs.
Which part of the lung is damaged in pneumonia?
The alveoli and the small bronchioles, which become filled with fluid and mucus, reducing oxygen uptake and causing breathlessness.
How does pneumonia spread?
Through droplets and aerosols from an infected person's cough or sneeze, and by sharing articles such as glasses and utensils with patients.
How is pneumonia different from the common cold?
Pneumonia is a bacterial infection of the alveoli with fever, chills and bloody sputum, while the common cold is a viral infection of the nose and respiratory passages that spares the lungs.
Is Haemophilus influenzae a virus?
No — despite its name it is a bacterium, and it is one of the two recognised bacterial causes of pneumonia.