Question

Write a short note on infectious diseases.

Hint:

Infectious = caused by a pathogen AND transmissible between individuals.

Answer 1

Step 1: Definition:
Infectious diseases are diseases caused by pathogenic microorganisms — bacteria, viruses, fungi, protozoa or helminths — that can be transmitted from an infected person to a healthy one.

Step 2: Modes of transmission:
They may spread through air (e.g. common cold, tuberculosis), contaminated water or food (e.g. typhoid, cholera), direct physical contact (e.g. ringworm), or via a vector such as a mosquito (e.g. malaria, dengue).

Step 3: Examples:
Examples across pathogen groups include: bacterial — typhoid (Salmonella typhi); viral — common cold (Rhinovirus); protozoan — malaria (Plasmodium); fungal — ringworm.

Final Answer:
Infectious diseases are caused by transmissible pathogens and spread via air, water, contact, or vectors; examples include typhoid, the common cold, malaria and ringworm.