Pathogenic micro organisms generally have a definite path by which they
• enter the body of a person , and
• leave the body of an infected person to find new hosts.
These path of entry and exit from the host determine how these micro organisms are spread or transmitted to new hosts.
Pathogens can spread through
• air, I.e. air borne pathogens,
• water, I.e. water borne pathogens,
• food, I.e. food borne pathogens,
• direct skin contact, and
• animals vectors.
Spread through air
Many disease causing organisms are light or have light spores which can easily float in air. These air borne pathogens enter the body of a person in the air he breathes through the nose and mouth. They often affect the nose, throat, trachea, bronchi and lungs. They also leave the body of the infected persons in droplets in the air he breathes out, and when he sneezes, coughs and spits. Disease like pneumonia, tuberculosis, influenza and mumps are caused by air borne pathogens.
Spread through Water
Certain disease causing organisms are spread by drinking contaminated water. Thus, these water borne pathogens enter their new host through his mouth. They often affect their intestines of their host, causing diarrhoea. They leave the body of their host via his faeces. In places where sanitation and personal hygiene are poor, drinking water can easily become contaminated by such infected body wastes. Diseases like typhoid and cholera are caused mainly by water borne pathogens.
Note some people can harbour pathogenic organism in their bodies without showing any signs of disease. These people are known as carriers. a carrier is a source of infection. For example, the faeces and urine of a person who is a carrier of water borne disease will be full of the pathogens causing that disease.
Spread through Food
Pathogenic organisms can be spread by eating contained food. Like water borne pathogens, food borne pathogens enter and leave the body of their host via the mouth, and in the faeces and urine, respectively. Food borne pathogens also tend to affect the intestines.
Food becomes easily contaminated
• when handled by infected persons or carriers who have poor personal hygiene habits;
• by contaminated water;
• by animal vectors like flies.
Foods milk and ice cream are some of the most common sources of infection as pathogens can multiply rapidly in these foods. This is because they contain all the nutrients needed for microbial growth. Diseases like bacillary dysentery, amoebic dysentery, salmonella food poisoning and cholera are caused by food borne pathogens.
Spread through direct skin contact
Certain pathogenic organisms are spread from one person to another by direct physical or skin contact. The diseases they cause are known as contagious diseases.
Physical contact occurs in crowded places, when playing games, and during activities like kissing and sexual inter course. Suing the personal things of a person with a contagious disease can also cause infection.
Contagious diseases usually affect the skin and mucous membranes. Leprosy, ringworm, yaws, syphilis and gonorrhea are examples of contagious diseases.
Note : scabies , a common contagious diseases, is caused by itch mites. The female mites burrow into skin and lay eggs. This causes severe itchiness in the affected parts.
Spread through animal vectors
Animals , especially insects, can spread diseases causing organisms from person to person.
