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Infection and Transmission
Infection occurs when pathogens establish themselves in a host, while transmission describes how they spread between sources and hosts.
#Infection is more than the presence of a microbe
CDC explains that germs are found in everyday environments and in and on the body; some are helpful and others harmful. Its infection overview describes germs entering the body, increasing in number and causing a host reaction. Colonization is a different term: germs can be present without symptoms of infection, and a colonized person can still transmit them.
These distinctions explain why the presence of a microbe and the spread of a microbe are different questions. They do not let this page decide whether a personal test shows colonization or disease, or whether someone without symptoms is safe to be around others.
Evidence: CDC: infection control basics
#A pathway connects a source with a host
CDC calls the place an infectious agent lives a source or reservoir, and describes transmission as its movement to a susceptible person. Its NERD Academy lesson uses the agent, the way it spreads and the ways it exits and enters hosts to build a chain-of-infection model.
That model separates the source, route and host instead of treating exposure as a complete explanation. It is a framework for learning, not a way to trace an individual's infection or calculate the chance of illness after a particular contact.
Evidence: CDC: infection control basics / CDC NERD Academy: how disease spreads
#Routes differ with the agent and setting
In healthcare examples, CDC describes physical contact, sprays and splashes, inhalation and sharps injuries as ways germs can move. Sources include people, surfaces and moist environments. These examples show that transmission can involve the environment or equipment as well as direct contact between people.
The examples are not a claim that every infectious agent uses every route. Disease-specific and setting-specific information is needed for practical decisions. This general page gives no isolation period, workplace clearance, post-exposure advice or instructions for managing an outbreak; Mynd does not provide infection-control services.
Evidence: CDC: infection control basics / CDC NERD Academy: how disease spreads
Source note
The sections above were checked against the linked sources. No clinical review has been performed. This is general research education, not a clinical guideline.