modes of infectious disease transmission

direct

pathogens pass immediately from an infected person or reservoir to a new host through close physical contact or short-range droplets

indirect

a pathogen transfers from a reservoir to a host using an intermediary, such as an object, air, or a vector

vertical

passage of an infectious pathogen from a mother to her embryo, fetus, or newborn baby

horizontal

the spread of infections between individuals of the same or different species, usually within the same generation

direct vertical

transplacental, childbirth, breast feeding

direct horizontal

intercourse, short-distance airborne, fecal-oral, transfusion, organ transplant

vehicle borne (indirect)

fomite becomes contaminated with an infectious agent and passively carries it to a new host (food, water, surfaces)

vector borne (indirect)

transmitted to humans by vectors like mosquitoes, ticks, fleas, etc.

parenteral (indirect)

pathogens bypass the body’s primary barriers and enter directly into the blood, tissue, or deeper laters (needlestick injuries, injection drug use, medical procedures, animal and human bites)