Communicable diseases are transmitted broadly by two modes: 

1. Direct transmission: It is by 

(a) Direct contact: From skin to skin. Examples: eye infection (conjunctivitis), skin diseases, etc. 

(b) Droplet infection: From droplet of saliva or nose during cough, sneezing, speaking and spitting. 

Examples: Tuberculosis (TB), common cold, whooping cough, influenza. 

(c) Contact with soil. Example: mycosis, tetanus. 

(d) Inoculation into skin: Microbes may inoculate directly into skin. Examples: Rabies virus is inoculated by dog bite, hepatitis B virus is inoculated through contaminated needles and syringes. 

2. Indirect transmission: It is by 

(a) Transmission of microbes through water and food (vehicle borne transmission). Examples: typhoid, cholera, polio, food poisoning, diarrhoea etc. 

(b) Transmission by blood. Examples: Hepatitis B and malaria. 

(c) Transmission of microbes by an arthropod/living carrier (vector borne). Examples: malaria, dengue are transmitted by mosquito, typhoid, cholera are transmitted by housefly, plague is transmitted by rat flea, etc.

(d) Transmission through fomites: Fomites include soiled clothes, towel, cups, spoon, toys, etc. Examples: diptheria, eye and skin infection.

(e) Transmission through unclean hands. Examples: typhoid, intestinal parasites.

(f) Air borne transmission. Examples: epidemic typhus.