Infectious Diseases: Definition & Types

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Infectious diseases can be as mild as the flu or as deadly as Ebola. In this lesson, you'll learn about infectious diseases: what they are, some examples of common ones, and how to prevent and treat them.

What are Infectious Diseases?

I love my friends and family, but when they have the flu I like to keep my distance. This is because they have an infectious disease, one that can be spread from them to me! Infectious diseases are caused by things that we can't even see, such as viruses, bacteria, fungi, and parasites. Not all infectious diseases are transmitted the same way, either. Some may be shared through direct contact, others through bodily fluids, and still others through another organism that is not affected by the disease but acts as a carrier.

How Infectious Diseases are Spread

You're probably quite familiar with many infectious diseases. I'm not implying that you've had them, I'm just guessing that you've heard of them. That's because spreading the word about infectious diseases is a great way to keep infectious diseases from spreading in the first place!

Chickenpox is a highly contagious disease that is quite uncomfortable for those unlucky enough to get it.
chicken pox

When I got chickenpox as a kid, I had to stay home so that I wouldn't spread it to the other kids in my class because it's shared through contact. As I got older I was warned about sexually transmitted diseases, which are also spread through close physical contact. Viral meningitis is a concern on college campuses, as is hepatitis, pneumonia, and even strep throat because of dorm life and other social interactions on campus. HIV is a lifelong virus that is spread through the exchange of bodily fluids, and I'm sure you're well aware of the recent outbreak of Ebola, a very deadly infectious disease that spreads quickly, also through contact of infected bodily fluids.

Human contact isn't the only way an infectious disease spreads, though. Malaria and West Nile viruses are spread through infected mosquitos, Lyme disease through ticks, rabies through infected mammal bites, and even the spread of the plague was largely assisted by rodents.

Mosquitoes are carriers of Malaria and West Nile virus, both of which are infectious diseases.

Fungal diseases can also be contagious, such as athlete's foot and other fungal skin and nail infections. You can contract a fungal infection in your lungs by breathing fungus in from the air, and though rare, fungal meningitis can travel from your blood to your spinal cord, making you very sick.

Prevention and Treatment

Hand washing is a great way to prevent the spread of infectious diseases.
hand washing

The spread of many infectious diseases can be prevented by proper hygiene and vaccinations. For example, if you are sick and you sneeze onto your hands, simply washing your hands will prevent you from spreading the disease that way. Taking appropriate precautions during sexual activity will limit your risk of contracting (or spreading) a sexually transmitted disease. Vaccinations for polio, hepatitis, and malaria can help your body build up a natural defense in case you ever come in contact with these diseases. Staying home when you're sick with the flu will prevent you from sharing it with your friends, co-workers, and anyone else you may come in contact with (they'll thank you later!).

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