How Infections Spread

Germs are a part of everyday life and are found in our air, soil, water, and in and on our bodies. Some germs are helpful, others are harmful. Many germs live in and on our bodies without causing harm and some even help us to stay healthy. Only a small portion of germs are known to cause infection.

How Do Infections Occur?

An infection occurs when germs enter the body, increase in number, and cause a reaction of the body.

Three things are necessary for an infection to occur:

• Source: Places where infectious agents (germs) live (e.g., sinks, surfaces, human skin)
• Susceptible Person with a way for germs to enter the body
• Transmission: a way germs are moved to the susceptible person

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• Source
• Susceptible Person
• Transmission

Source

A Source is an infectious agent or germ and refers to a virus, bacteria, or other microbe.

In healthcare settings, germs are found in many places. People are one source of germs including:

• Patients
• Healthcare workers
• Visitors and household members

People can be sick with symptoms of an infection or colonized with germs (not have symptoms of an infection but able to pass the germs to others).
Germs are also found in the healthcare environment. Examples of environmental sources of germs include:

• Dry surfaces in patient care areas (e.g., bed rails, medical equipment, countertops, and tables)

Wet surfaces, moist environments, and biofilms (e.g., cooling towers, faucets and sinks, and equipment such as ventilators)