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

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.

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

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.

Adverse functioning of one or more organs or systems of the body, characterised by specific signs and symptoms, is called disease.

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

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

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

The microbes that cause disease are called pathogens.

Example : Bacteria, virus, etc

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

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.

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

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

• Communicable / Infectious diseases are caused by pathogens and spread from an infected to a healthy person via air, water, food, vectors, or contact.
• Common pathogens: bacteria (cholera, typhoid, TB), viruses (AIDS, hepatitis), protozoa (malaria), and helminths (ascariasis, filariasis).
• Incubation period: time between infection and symptoms — varies from hours (cholera) to years (HIV/AIDS, leprosy).
• TB (Mycobacterium tuberculosis) spreads through air; prevented by BCG vaccine, isolation, and DOTS.
• Hepatitis spreads through contaminated water, needles, or blood; prevented by boiled water and hygiene.
• Cholera, typhoid, and dysentery spread through contaminated food and water; prevented by hygiene, boiled water, ORS, and vaccination.

• Vaccination and immunisation work on the immune system's memory.
• A vaccine may contain a weakened pathogen, an inactivated pathogen, or antigenic proteins.
• The body produces antibodies against these antigens.
• Memory B-cells and T-cells enable a faster response during later exposure.
• Passive immunisation involves direct injection of preformed antibodies or antitoxins.
• Examples of passive immunisation include tetanus and snakebite treatment.
• Vaccines may be made from protein or sugar from a pathogen, a dead or inactivated pathogen, a toxoid, or a weakened pathogen.
• Antigenic polypeptides can also be produced using recombinant DNA technology in bacteria or yeast.