The National Academies: What You Need To Know About Infectious Disease

The National Academies

What You Need To Know About Infectious Disease

How Infection Works

Microbes occupy all of our body surfaces, including the skin, gut, and mucous membranes. Most don’t do us any harm—in fact, many help us survive. But there are certain bacteria, viruses, and other microbial life forms that can cause illness, or even death. Here we learn the basics about microbes and the fascinating relationship we have with them.

Microbes & Humans

A human body contains at least 10 times more bacterial cells than human ones.

Microbes and humans have evolved a complex relationship over thousands of years. Find out just how interconnected we are.

More about microbes & humans

Types of Microbes

There are five major categories of infectious agents. 

Viruses, bacteria, and helminths—oh my! Learn about the different microorganisms that are the source of infectious disease in people.

More about types of microbes

Encountering Microbes

Microbes may be the earliest life forms on Earth.

People and microbes have always shared this planet. But changes in the way we live are affecting how and where we encounter microbes. Discover the impact of our modern way of life.

More about encountering microbes

How Pathogens Make Us Sick

Infection does not necessarily lead to disease.

Pathogens (microbes capable of causing disease) call our immune systems into action. Find out more about how the body responds to these tiny invaders.

More about how pathogens make us sick

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Infectious Disease Videos

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What You Need to Know About Infectious Disease

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Disease Watchlist

What do you know about infectious disease?

The 1918 influenza pandemic (the so-called “Spanish” flu) is estimated to have killed how many people worldwide?

  • Sorry, that’s incorrect.

    The 1918 influenza pandemic is estimated to have killed between 50 million and 100 million people worldwide. Many of those deaths were due to the effects of pneumococcal pneumonia, a secondary complication of flu for which no antibiotics existed in 1918.

  • Sorry, that’s incorrect.

    The 1918 influenza pandemic is estimated to have killed between 50 million and 100 million people worldwide. Many of those deaths were due to the effects of pneumococcal pneumonia, a secondary complication of flu for which no antibiotics existed in 1918.

  • Correct!

    The 1918 influenza pandemic is estimated to have killed between 50 million and 100 million people worldwide. Many of those deaths were due to the effects of pneumococcal pneumonia, a secondary complication of flu for which no antibiotics existed in 1918.

Infectious Disease Defined

Cirrhosis

A condition caused by chronic liver disease characterized by the development of scar tissue leading to a loss of liver function.

View our full glossary

National Academies Press

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