Revision: Infectious Diseases and How to Prevent Them Environmental Studies 1 SSC (English Medium) 5th Standard Maharashtra State Board

A pathogen is a biological agent that causes disease to its host. e.g. bacteria, virus, etc.

Disease:
The disease can be defined as an impairment or malfunctioning of the normal state of the living organism that disturbs or modifies the performance of vital functions of the body.

Any deviation from normal state of health is called disease.

A disease caused by a specific pathogenic organism and capable of being transmitted to another individual by direct or indirect contact is known as communicable (infectious) disease.

Droplet infection is an infection transmitted from one individual to another by droplets of saliva or nasal moisture during coughing, sneezing, speaking and spitting.

A vector is an organism that carries disease causing microbes (pathogens) from one host to another. They are the carriers of infection.

Example: Mosquito, housefly, etc

The diseases which spread from an infected person to a healthy person through air, water, food, soil or physical contact are called communicable diseases.

Example : Common cold, chickenpox, etc

The microbes that cause disease are called pathogens.

Example : Bacteria, virus, etc

The process of administering a vaccine to stimulate the immune system and provide protection against infectious diseases is called vaccination.

Infection is the entry, development, or multiplication of an infectious agent in the human body or animals.

Preparation of antigenic proteins of pathogens (weakened or killed) which on inoculation into a healthy person provides temporary/permanent immunity against a particular disease.

Antibiotics are metabolic products of microorganisms whose very low concentrations are inhibitory or detrimental to other microbes.

A preparation containing specific antigens that is administered to induce temporary or permanent immunity against a particular disease is called a vaccine.

• Principle: Works on the immune system's memory. A vaccine (weakened/inactivated pathogen or its proteins) stimulates antibody production and generates memory B and T-cells.
• On Re-exposure: Memory cells quickly recognise the pathogen and produce massive antibodies to neutralise it.
• Passive Immunisation: Preformed antibodies/antitoxins are directly injected when quick response is needed (e.g., tetanus, snakebite).
• Types of Vaccines: Protein/sugar from pathogen, dead/inactivated pathogen, toxoid, or attenuated (weakened) pathogen.
• Recombinant DNA Vaccines: Antigenic polypeptides produced in bacteria/yeast for large-scale production (e.g., Hepatitis B vaccine from yeast).