Contagious vs. Infectious: Understanding the Difference

Understanding the Difference Between Contagious and Infectious

Many people mix up the words “contagious” and “infectious” because they both have to do with spreading illness. But, they are not the same. Let’s learn about each one and when to use them.

History of the Words

The word “contagious” comes from an old Latin word “contagiosus,” which means “to touch.” It first came to English in the 14th century to describe diseases that spread easily from one person to another by touch.

On the other hand, “infectious” comes from the Latin word “infectus,” meaning “to stain or spoil.” It entered English use in the 14th century too, but it refers to diseases caused by germs like bacteria or viruses.

How to Use Them

Contagious: This word means you can get the disease from someone else by being near them or touching things they have touched.

• The flu is contagious; it spreads easily from person to person.
• A cold is very contagious, especially in crowded places.
• Her laughter was contagious; soon everyone was laughing.
• Chickenpox is a contagious disease that causes itchy skin.
• Mom told me to wash my hands because the sickness is contagious.

Infectious: This word is about diseases that spread from germs, but not always by direct touch from one person to another.

• The doctor said the infection was caused by an infectious germ.
• This bacteria can be infectious if it gets into your body.
• Some infectious diseases can spread through the air.
• Measles is an infectious disease that can be stopped by a vaccine.
• The scientist studies different infectious viruses in the lab.

Trick to Remember the Difference

Think of “contagious” like when you “catch” it because someone touched something you touched, or they were very close to you. “Infectious” means the disease is spread by germs, but not always by touch.

Summary of the Usage

Use “contagious” when talking about diseases that spread easily by touch or being near someone. Use “infectious” when referring to diseases caused by germs, which do not always need touch to spread.