Chapter 2

Virus

|Chapter 2: What is a virus and how can viruses affect you?|

A virus is a non-living, super microscopic (many times smaller than bacteria!) structure of nature that connects to tissue inside its host (animal or plant) often causing infection (sickness) and disease. Viruses contain chemical structures called DNA and RNA that are surrounded by a protein wall. DNA contains the code that in a way tells the virus what to do which is mainly to reproduce to spread throughout the host. This is what makes us sick!

When viruses take over the cells in a host, they inject their DNA into the DNA of the host cell. This leads to more viruses. The more viruses reproduce, the more they take over cells of the host’s body. This leads to the host becoming sicker.

Let's watch a video that shows how a virus enters our body and makes us sick.

Scientists and doctors create vaccines to fight viruses. Scientists develop a weakened version of a virus which is made into a vaccine (medicine). The idea is that if we put a weak version of the virus into our bodies that our body will fight and destroy it. This builds up our resistance to the virus. So when we do get the virus, our bodies know how to destroy it.

We take vaccines usually by injection (a shot). The vaccine helps our immune system prevent specific viruses from making us sick. One difficulty with viruses is that they change over time. This means that the vaccines created for a specific virus will not work as the virus changes its chemical structure. It is this changing that makes it so difficult to stop viruses from spreading. A vaccine might work to stop one type or strain of a virus but the changing virus might be immune to the vaccine.

The BBC has a short video that shows how a vaccine injected into the body will fight the virus (pathogen) by making the body produce anti-bodies against it. The video uses some big words but it is worth watching to see how a vaccine works. Now watch the video and then come back here to go to the next chapter.

What are some diseases caused by virus infections?

  • Common Cold

  • Chickenpox

  • Influenza (the flu)

  • Mumps

  • Polio

  • Smallpox

  • Warts

We get vaccines through shots when we go to the doctor to prevent us from getting all the diseases in the list. You might remember getting what we call a flu shot each year. The flu shot is a vaccine against the influenza virus. Each year scientists take flu viruses from the previous flu season to create a vaccine. The vaccine contains a little of the virus that is no longer active. Once it is injected into your body, your natural defenses in the form of antibodies multiply as they destroy the weakened virus in the vaccine. Your body now has built up the antibodies that are ready in case you get the flu.

Now how about playing a game and visiting a website to learn about cells? Visit the sites but then return here to go to the next chapter.

  • Go to a game that let’s you get a feel for how antibodies attack viruses like the influenza virus.

  • Take a look at what a cell looks like.

Let's take a look at Chapter 3

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