How are infections transmitted?

Infections are caused by microorganisms, which are tiny organisms that can only be seen under a microscope. If you could look at your environment under a microscope, you would see that microorganisms are everywhere--on your skin, in the air you breathe, and in people, animals, plants, soil, and water.

Some microorganisms are normally present on your skin and in your respiratory, intestinal, and genital tracts. These are called normal flora. Other microorganisms are normally not found on or in the human body and are usually associated with disease. These are known as pathogens.

Infections are transmitted when microorganisms are transferred from a contaminated person or object to another person. All microorganisms, including normal flora, can cause infection or disease. Normal flora found on the skin of a service provider may cause infection when introduced into an area of the body where they are not normally found, such as into a client's internal organs during surgery. Normal flora can also cause infection in an immunocompromised person who is especially susceptible to infection.

For example:

• If you pick up a contaminated object, microorganisms from that object can contaminate your hand.
• If you touch other objects or persons with your contaminated hand, you can pass the microorganisms on to them.
• If you have a cut on your hand when you touch a contaminated object, the microorganisms can enter your bloodstream and cause an infection.

Modes of transmission

There are four ways that infections are transmitted:

• Contact - Direct transfer of microorganisms through touch (staphylococcus), sexual intercourse (gonorrhea, HIV), fecal/oral transmission (hepatitis A, shigella), or droplets (influenza, TB)
• Vehicle - Material that serves as a means of transfer of the microorganisms. This can be food (salmonella), blood (HIV, HBV), water (cholera, shigella), or instruments and other items used during clinical procedures (HBV, HIV, pseudomonas)
• Airborne - Microorganisms can be carried by air currents (measles, TB)
• Vector - Invertebrate animals can transmit the microorganisms (mosquito: malaria and yellow fever; flea: plague)

Transmission of
HIV & hepatitis B...

All microorganisms, including normal flora, can cause infection or disease under certain circumstances.

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