A method of transmission is the movement or the transmission of pathogens from a reservoir to a susceptible host. Once a pathogen has exited the reservoir, it needs a mode of transmission to the host through a portal of entry. Transmission can be by direct or indirect contact or through airborne transmission.
Direct contact is person-to-person transmission of pathogens through touching, biting, kissing, or sexual intercourse. Microorganisms can also be expelled from the body by coughing, sneezing or talking. The organisms travel in droplets over less than 1 metre in distance and are inhaled by a susceptible host.
Indirect contact includes both vehicle-borne and vector-borne contact. A vehicle is an inanimate go-between, an intermediary between the portal of exit from the reservoir and the portal of entry to the host. Inanimate objects such as handkerchiefs and tissues, soiled laundry, and surgical instruments and dressings are common vehicles that can transmit infection.