There are many routes by which germs gain entry into human body. They are generally spread in one or more of following ways:

• Direct contact:- Infection is spread by contact between the person who is affected with disease with another person by bodily contacts like hand shaking etc.

• Air:- During coughing, sneezing and speaking loudly, small drops of sputum which are laden with germs are sprayed into the air. The air of crowded places, classrooms, cinema halls and ill-ventilated houses is often full of different kinds of germs. When this air is inhaled by a healthy person, the infection is conveyed to him. Infectious diseases like diphtheria, whooping cough, measles, influenza and common cold spread through air.

• Food and drink:- Flies sit on exposed articles of eating & drinking and thus deposit germs of various diseases such as typhoid, diarrhea etc to spread

• Bites of insects:- Certain insects causes disease through bites on the skin. The example of this type of diseases includes malaria, dengue etc.

• Cuts in skin:- Sometimes there occur cuts in the skin through accidents or sharp blades, knives and other similar weapons. Germs enter through such cuts in the skin and spread infectious diseases like tetanus,syphilis etc.

• Diseases carriers:- When a person possess disease germs and passes on to other, without becoming ill from them himself, he is known as a disease carrier. It means that his body is immune to disease causing germs in a very active form.Diseases such as typhoid fever may spread in this way.

• Through genital passage:- The organism of venereal diseases gain access to the body via the genital passages. Diseases like syphilis etc may spread in this way.