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Pneumonia: Causative Bacteria (Streptococcus, Haemophilus) and Symptoms

Biology · Human Health and Diseases · NEET

Pneumonia is a bacterial disease of the lungs caused by two bacteria: Streptococcus pneumoniae and Haemophilus influenzae. These bacteria infect the alveoli (the tiny air sacs of the lungs), which then fill with fluid and cause breathing problems. Memory hook: "Strep and Haemo flood the alveoli" — two bacteria, one target (alveoli), symptoms are fever, chills, cough and headache.
Pneumonia: Bacteria Infect the AlveoliCausative BacteriaStreptococcus pneumoniaeHaemophilus influenzaeAlveoli (lungs)fill with fluidbreathing problemSymptomsFever, chills,cough, headacheSevere case: lips and finger nails turn grey to bluish (low oxygen)Two bacteria - one target (alveoli) - four symptoms
Pneumonia is caused by the bacteria Streptococcus pneumoniae and Haemophilus influenzae, which infect the alveoli of the lungs. The alveoli fill with fluid, causing fever, chills, cough and headache; in severe cases lips and nails turn bluish.

Your doubts, answered

What bacteria cause pneumonia according to NCERT?

NCERT clearly states two bacteria cause pneumonia in humans: Streptococcus pneumoniae and Haemophilus influenzae. For NEET, remember BOTH names. In match-the-column PYQs, the option often shows only one of them (usually Haemophilus influenzae or Streptococcus pneumoniae), and either can be the correct pair for pneumonia.

Is pneumonia caused by a virus or a bacterium?

Pneumonia, as tested in NEET from NCERT, is a BACTERIAL disease. The two causative bacteria are Streptococcus pneumoniae and Haemophilus influenzae. Do not confuse it with the common cold, which is caused by rhinoviruses (a virus). This bacteria-vs-virus difference is a common trap.

Which organ or part does pneumonia infect?

Pneumonia infects the alveoli — the air-filled sacs of the lungs where gas exchange happens. NCERT says the alveoli get filled with fluid due to the infection, which leads to severe problems in respiration (breathing). So the target is the lungs, specifically the alveoli.

What are the symptoms of pneumonia?

The NCERT symptoms of pneumonia are: fever, chills, cough and headache. In severe cases, the lips and finger nails may turn grey to bluish in colour because of low oxygen. Learn the four core symptoms in order — fever, chills, cough, headache — as NCERT lists them.

Is Haemophilus influenzae the same as the influenza (flu) virus?

No. This is a big trap. Haemophilus influenzae is a BACTERIUM that causes pneumonia. The name only sounds like influenza. The influenza virus (flu) is a completely different virus. NEET options use this confusion, so remember: Haemophilus influenzae = bacterium = pneumonia.

⚠️ The NEET trap
✗ Pneumonia is caused by Plasmodium or by a virus, and Haemophilus influenzae causes the flu.
✓ Pneumonia is caused by the bacteria Streptococcus pneumoniae and Haemophilus influenzae; both infect the alveoli. Haemophilus influenzae is a bacterium, not the flu virus.
🧠 In match-the-column questions, pneumonia always pairs with a BACTERIUM (Streptococcus or Haemophilus). If you see Plasmodium (malaria) or a virus next to pneumonia, it is wrong.

Real NEET questions

NEET 2020

Match the following diseases with the causative organism and select the correct option. Column-I: (a) Typhoid (b) Pneumonia (c) Filariasis (d) Malaria. Column-II: (i) Wucheria (ii) Plasmodium (iii) Salmonella (iv) Haemophilus

A · (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
B · (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
C · (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
D · (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii) ✓
Solution: Typhoid = Salmonella (iii); Pneumonia = Haemophilus influenzae (iv); Filariasis = Wuchereria (i); Malaria = Plasmodium (ii). So a-iii, b-iv, c-i, d-ii. Note pneumonia pairs with the bacterium Haemophilus.
NEET 2021

Match List I with List II. List I: (a) Filariasis (b) Amoebiasis (c) Pneumonia (d) Ringworm. List II: (i) Haemophilus influenzae (ii) Trichophyton (iii) Wuchereria bancrofti (iv) Entamoeba histolytica

A · (a)-(i); (b)-(ii); (c)-(iv); (d)-(iii)
B · (a)-(ii); (b)-(iii); (c)-(i); (d)-(iv)
C · (a)-(iv); (b)-(i); (c)-(iii); (d)-(ii)
D · (a)-(iii); (b)-(iv); (c)-(i); (d)-(ii) ✓
Solution: Filariasis = Wuchereria bancrofti (iii); Amoebiasis = Entamoeba histolytica (iv); Pneumonia = Haemophilus influenzae (i); Ringworm = Trichophyton (ii). So a-iii, b-iv, c-i, d-ii. Pneumonia again matches the bacterium Haemophilus influenzae.
NEET 2023 Phase 1

Match List I with List II. List I: A. Ringworm B. Filariasis C. Malaria D. Pneumonia. List II: I. Haemophilus influenzae II. Trichophyton III. Wuchereria bancrofti IV. Plasmodium vivax

A · A-II, B-III, C-IV, D-I ✓
B · A-II, B-III, C-I, D-IV
C · A-III, B-II, C-I, D-IV
D · A-III, B-II, C-IV, D-I
Solution: Ringworm = Trichophyton (II); Filariasis = Wuchereria bancrofti (III); Malaria = Plasmodium vivax (IV); Pneumonia = Haemophilus influenzae (I). So A-II, B-III, C-IV, D-I. Pneumonia is caused by the bacterium Haemophilus influenzae.

Solved Human Health and Diseases NEET PYQs

Try the real previous-year questions from this chapter — each with the answer and a full solution.

See all 45 Human Health and Diseases NEET PYQs ›
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Frequently asked

Which two bacteria cause pneumonia?

Streptococcus pneumoniae and Haemophilus influenzae. NCERT names both, so remember them as a pair for NEET.

What part of the lung does pneumonia affect?

It infects the alveoli (air-filled sacs of the lungs). The alveoli fill with fluid, causing severe breathing problems.

What are the four main symptoms of pneumonia?

Fever, chills, cough and headache. In severe cases, the lips and finger nails may turn grey to bluish.

Is pneumonia bacterial or viral in NCERT?

For NEET, NCERT lists pneumonia as a bacterial disease caused by Streptococcus pneumoniae and Haemophilus influenzae.

Why do lips turn bluish in severe pneumonia?

Because the fluid-filled alveoli cannot take in enough oxygen, so blood oxygen drops and the lips and nails turn grey to bluish.

Related concepts:
Common Cold: Rhinoviruses and Why It Affects the Nose and ThroatTyphoid: Salmonella typhi, Symptoms and the Widal TestDisease and Causative Organism: How to Match ThemWhat Is a Pathogen? Meaning and Common ExamplesHow Infectious Diseases Spread: Modes of Transmission
Practise Biology for NEET:
Biology MCQs (free, chapter-wise)Human Health and Diseases PYQs