Bacteria, Fungi, Viruses

show/hide words to know

Airborne: moving through the air.

Antiseptic: a substance that is applied to skin to prevent infection by microorganisms.

Direct transmission: passing pathogens by the direct contact (touching) of two people.

Disinfectant: a substance that is applied to non-living surfaces to kill microorganisms.

Indirect transmission: passing pathogens from one person to another by way of an intermediate object, like a doorknob.

Passing Pathogens

Sneezing man

Airborne transmission is the passing of pathogens through the air. This happens most often when people sneeze or cough. Image by James Gathany via the CDC.

You are sitting in class, reading. The room is quiet and no one is talking. A sudden loud noise causes you to jump. Someone has sneezed. It was especially loud because they didn’t cover their mouth. You don’t think much of it and go back to reading.

Two days later, more people are sneezing. The day after that, half of your class is sick at home. How did this happen? You think back to the sneeze. Was that how it started?

Did you know that when a person sneezes, water droplets from their mouth and nose rush out at up to 150 feet per second? That’s over 100 miles per hour!

Baby touching hand, direct transmission

Direct transmission can occur when direct contact is made between two people. A baby grabbing your finger is a good example of direct contact. Image by Rufino.

Additionally, a single sneeze can release around 40,000 separate droplets of liquid that might carry pathogens. This can spread pathogens over a wide area and can cause many infections. The spread of pathogens in this way is called airborne transmission.

A lot of pathogens cause symptoms, or signs of illness, like sneezing and coughing. This way, they can spread, infecting as many people as possible. This is why it is so important to cover your mouth when you sneeze and to wash your hands.

Limiting the Spread of Infection

The very best way to prevent catching or spreading a pathogen is to wash your hands regularly with soap and water.


Indirect transmission occurs when one person touches something, like this doorknob, leaving behind germs. When another person touches it, they pick up some of the germs. Image by Joel McCoy.

There are two kinds of person-to-person disease transmission: direct contact and indirect contact. Direct contact is when one person transfers a pathogen to another by direct touch. This can happen in the form of a handshake for example.

Indirect contact occurs when someone with a disease touches an object and accidentally leaves some of the pathogen. The next person who touches that object can get infected.

To prevent these kinds of transmission, we can use antiseptics and disinfectants. Antiseptics are used on our skin, like the soap we use when we wash our hands. Disinfectants are used to kill microorganisms on surfaces, but not the skin.

Images via Wikimedia Commons.

View Citation

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Bibliographic details:

  • Article: Passing Pathogens
  • Author(s): Steven Hart
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: July 24, 2014
  • Date accessed: June 12, 2024
  • Link:

APA Style

Steven Hart. (2014, July 24). Passing Pathogens. ASU - Ask A Biologist. Retrieved June 12, 2024 from

American Psychological Association. For more info, see

Chicago Manual of Style

Steven Hart. "Passing Pathogens". ASU - Ask A Biologist. 24 July, 2014.

MLA 2017 Style

Steven Hart. "Passing Pathogens". ASU - Ask A Biologist. 24 Jul 2014. ASU - Ask A Biologist, Web. 12 Jun 2024.

Modern Language Association, 7th Ed. For more info, see
Cover coughs, cover sneezes

People have known how to decrease transmission of pathogens for decades. This ad from the 1940s urges you to cover your coughs and sneezes.

This activity has a companion experiment Let the Germs Begin.

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