What is the difference between infectious and non-infectious diseases?

Infectious (communicable) diseases are caused by pathogens (bacteria, viruses, fungi, protozoa, or worms) and can spread from one person to another through air, water, food, physical contact, or vectors like mosquitoes. Examples: cholera, malaria, tuberculosis. Non-infectious diseases cannot spread between people — they are caused by genetic factors, nutritional deficiencies, lifestyle, or environmental factors. Examples: diabetes, cancer, deficiency diseases.

Why don't antibiotics work against viral infections?

Antibiotics target specific bacterial cell structures like cell walls, ribosomes, or enzymes that bacteria have but human cells do not. Viruses are fundamentally different — they do not have cell walls or their own metabolism; they use the host's cellular machinery to replicate. So antibiotics have no target to attack in viruses. Antiviral drugs are needed for viral infections, though these are much harder to develop.

How does vaccination prevent disease?

Vaccination introduces a weakened, killed, or partial form of a pathogen into the body. The immune system mounts a response and creates 'memory cells' (memory B and T lymphocytes). If the real pathogen enters later, the immune system recognises it quickly and destroys it before symptoms appear — the person is immune. Examples: BCG vaccine for TB, OPV for polio, hepatitis B vaccine.

Diseases and Health

Why Do We Fall Ill • Class 9 Science • NCERT • CBSE

Health is a state of complete physical, mental, and social well-being. Diseases can be acute or chronic, infectious or non-infectious. Infectious diseases are caused by pathogens (bacteria, viruses, fungi, protozoa, worms) and can spread from person to person.

Frequently Asked Questions

What is the difference between infectious and non-infectious diseases?: Infectious (communicable) diseases are caused by pathogens (bacteria, viruses, fungi, protozoa, or worms) and can spread from one person to another through air, water, food, physical contact, or vectors like mosquitoes. Examples: cholera, malaria, tuberculosis. Non-infectious diseases cannot spread between people — they are caused by genetic factors, nutritional deficiencies, lifestyle, or environmental factors. Examples: diabetes, cancer, deficiency diseases.
Why don't antibiotics work against viral infections?: Antibiotics target specific bacterial cell structures like cell walls, ribosomes, or enzymes that bacteria have but human cells do not. Viruses are fundamentally different — they do not have cell walls or their own metabolism; they use the host's cellular machinery to replicate. So antibiotics have no target to attack in viruses. Antiviral drugs are needed for viral infections, though these are much harder to develop.
How does vaccination prevent disease?: Vaccination introduces a weakened, killed, or partial form of a pathogen into the body. The immune system mounts a response and creates 'memory cells' (memory B and T lymphocytes). If the real pathogen enters later, the immune system recognises it quickly and destroys it before symptoms appear — the person is immune. Examples: BCG vaccine for TB, OPV for polio, hepatitis B vaccine.

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