Basic Disease Investigation Module One: Communicable Disease Basics

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Indirect Transmission

Indirect transmission occurs when an agent moves from a reservoir or host to another host by means of a living organism or an inanimate object. Examples of indirect transmission include:

Vehicle borne Transmission Transmission via a contaminated inanimate object, such as food, water, objects such as toys or bedding, medical devices, etc.   The organism may or may not multiply in or on the vehicle. One common type of vehicle borne infection is foodborne illness resulting from food prepared by an ill food handler.

Vector borne Transmission

Transmission via a living object (vector).   Examples of vector bone transmission include infection with West Nile virus and plague. Indirect transmission through the bite of a flea is the most common route of transmission between plague-infected rodents and humans.

Airborne Transmission Transmission via droplet nuclei, or aerosols, that remain airborne for long periods of time and are inhaled. Examples of diseases spread by airborne transmission include measles and tuberculosis. In contrast, droplets from coughs and sneezes are heavy and settle quickly, so transmission of agents contained in droplets is considered “direct.”