How the common cold works
By Marshall Brain
http://www.JewishWorldReview.com | (MCT) This week I have a cold. You know the drill - runny nose, cough, scratchy throat and phlegm. The average adult gets a cold two to four times a year, and kids get even more. So the obvious question is: How does the common cold work?
It all starts with a virus particle. And there are lots of different virus particles that can cause the symptoms that go with the common cold. You might have heard that it is hard to cure the common cold because there are so many viruses that cause it, and that is true. There are rhinoviruses, coronaviruses, adenoviruses and so on, all of which cause the same package of symptoms.
We pick up these virus particles from other people. When they sneeze or cough or wipe their noses, they release the virus particles that have been reproducing inside their bodies. Their particles spray into the air or wipe onto door knobs, banisters, telephones and so on. Eventually some of the particles land in your nose, and there is some chance that you will "catch a cold".
This brings up the obvious question: What is a virus particle? The first thing to understand is that a virus particle is not a living cell. It is not like a bacteria cell, or a cell in your body. That's why antibiotics won't work with a cold. Antibiotics kill living bacteria, not viruses.
Instead, a virus particle is a container holding a little bit of genetic material in the form of RNA or DNA. Once this genetic material from the virus particle gets inside a living cell (like one of the cells lining your nose), it tells the cell to make more virus particles. A virus particle hijacks a living cell to create more virus particles. It does not take very long for a few virus particles to become thousands of virus particles inside your body.
So the sequence of events looks something like this: A virus particle gets into your nose. There is a chance that it gets blown back out or swallowed. But there is also a chance that it enters one of your cells and tells the cell to start making more virus particles. The infected cell dies, bursts and releases thousands of new virus particles into your body. Those particles start infecting new cells. The whole reproductive cycle, from cell infection to cell bursting, takes about 10 hours.
As your cells start dying and bursting, your body starts to understand that something has gone wrong. It cranks up your immune system.
Your immune system does the same kind of thing that it does when you get a sunburn. This may sound odd, but when you get a sunburn, you actually can see your immune system in action. In a sunburn, infrared light in the sun kills skin cells. Your body senses the dead cells and activates the immune system to clean them up. Capillaries swell in the sunburn area to let more blood in (your skin gets red and warm from the extra blood flow), and nerve endings sense pain. The extra blood brings in fluids and white blood cells to clean up the damage.
Now imagine this same kind of thing happening in your nose and throat. Your immune system senses the dying cells, and it does the same kind of thing it does for a sunburn. The capillaries swell, bringing in more fluid and white blood cells. Your nose starts to run and gets stuffy. Pain cells are activated, leading to a sore throat and coughing.
In two to three days, the virus load in your nose and throat reaches its peak. As your immune system attacks the virus and cleans it out, things start getting better, and generally the symptoms are gone in 7 to 10 days. Meanwhile, after about 2 weeks, your body is producing antibodies that will prevent that one virus from attacking you again. The problem is, there are a hundred other cold viruses waiting in the wings.
It's funny - all the symptoms from a cold are actually caused by your own body, rather than by the cold virus. What you are seeing is your immune system doing its job to get rid of the virus particles.
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