How Does a Virus Work? Viral Mutations, Antigenic Shift and Drift

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The swine flu virus is an example of adaptive mutation. Image by the CDC

With all this talk about the novel norovirus and the H7N9 bird flu, you maybe hearing terms like ‘mutate’ and ‘antigenic drift.’ This would be the point where you remember back to being in class thinking, “when am I going to need this information?” Well folks, the time is now.  It is helpful to understand these terms so that you understand what’s going on with these new viruses. Here’s the grown-up, simplified, no test-required, mini lesson on viruses and how they work.

Viruses: The Beginning

It all starts with microbes, tiny little things that can either make you sick or keep you healthy. Microbes are divided up into four categories; bacteria, viruses, fungi, and parasites. Due to the new viruses circulating around, we will be focusing on viruses for today.

Viruses are some of the smallest things on earth, even smaller than bacteria; but unlike bacteria, viruses cannot survive on their own – they need to be inside another living cell; this cell is then called a host.

Think of it as going to a party: You are the virus and your friend’s house is the host, aka the cell. In order to dance at the party, you have to be inside your friend’s house. Same with a virus; the virus has to be inside the host to live. Once the virus is inside the host, they begin to make lots and lots of copies of themselves. Once the virus has made so many copies that the cell can’t contain them, then the cell bursts and these copies can then infect other cells. This is when you begin feel sick.

The Ever-Changing Virus

Your body is smart. Once you get sick with a virus, your immune system remembers this virus, so that the next time it can recognize the virus and fight it off. This also applies to animal’s immune systems as well. So the next time a virus tries to make its home in a human or animal’s cells, the virus may find that it cannot attach so easily. The virus is resilient as well, though – it works to change its make up so that it can trick the host’s cells into letting it in. This is mutation – when the virus changes its makeup. This process of the virus continually changing over time is known as antigenic drift. This is why th CDC recommends that you get the flu shot every year – each year’s flu virus is different than the year before.

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