The term ‘epidemiology’ is derived from “epidemic” which means ‘among people’ and “logy” mean ‘to study’. So epidemiology refers to the study of the variation in human environment and state health. It also gives the information about distribution and magnitude of diseases in human population at a place.
Transmission of communicable Diseases:
The communicable diseases are transmitted the source of infection to a susceptible individual by the inflections agents and the ecological condition etc. The diseases are communicated by direct ways and indirect ways. The direct transmission is made by. Direct contact, Droplet infection , contact_ with soil; inoculation into skin etc, and Indirect Transmission is made by – vehicle borne , vector borne such as mechanical arid Biological and Airborne by droplet unclear dust and unclear hands and figures .
Infection is made direct contact from skin to skin, mucosa to mucosa or mucosa to skin. The disease from affected individual to the susceptible man is possible by such direct contract.
By the process of a spray of droplets of saliva, and during coughing, sneezing speaking. The examples are common cold, diphtheria and tuberculosis etc.
Contact with soil:
The disease agent may be acquired by direct exposure of the susceptible sues to soil” compost or decaying materials etc. The example are hookworm, tetanus etc.
Inoculation into the skin:
The disease agent may be directly inoculated into skin. The examples are rabies, virus hepatitis etc.
It implies the transmission of the infectious agent through the of water, food etc. serum food and water are the common medium of transmission.
Water borne disease:
Various types of bacteria and chemicals are found in drainage water etc. concatenates the water sources and disease. Such water born diseases are biological and chemical. The biological agents are bacteria, protozoa’s viruses, parasites etc. and the chemical agents are minerals, metals, cynamides, pesticides, and organic aids and these agents pass into the drinking water and cause diseases.
Food borne disease are caused by agents that enter the body through the indigestion of food and such food born infection is caused by the organisms growing food large numbers. Cooked food when kept open, may be infected by soiled fat of flies sitting on, them similarly, uncooked food when kept open, soiled; eaten up by raw but not cleaned properly may cause infection. Raw meat when no cooked properly may transmit worms and also infected.
This means when any living carrier that transfect an infectious agent to a susceptible individuals by vector transmission agents like biting , scratching in of infective places, contamination of host with body fluids of vector .
The infections agent is mechanically transmitted by a crawling or flying vector through soiling of its fact. There is no development or multiplication of agent on or within the other.
The infection agent under goes application or development, or both in vector and requires an incubation period before vector can transmit.
The air borne infection is possible by the evaporation of droplets coughed or sneezed into the air, almost ting device and practical formed by accidentally in microbiological labs.
Droplets expelled during talking, coughing or sneezing, settle down by the sheer weight on the floor, carpets, furniture, clothes, bedding, liner etc. and become part of the dust. During sweeping, dusting and bed making the dust released into the air and becomes air borne. Such air borne dust settles on uncovered food and milk and transmit diseases.
Fumites are inanimate articles or substances or food contaminated by infections discharges tom a patient and capable or transferring the infection to a healthy person.
Unclean hands and figure:
By hands the pathogenic agents are transferred to food from the skin nose, bowel etc. Such transmission possible by hands and fingers to the mouth by indirect ways and caused communicable diseases.