So, I have a cold. A common cold. A rhinovirus.
There are a wealth of misconceptions surrounding the common cold. All of the supposed “cures” for the common cold have absolutely no evidence backing them up. This is what we know for sure: You get a cold. It will last about a week. A bit longer for children. You can control the symptoms, but other than that, there is nothing you can do about it. (Note: If you have faith in megadoses of vitamin C, go ahead… The power of the mind is great indeed, and I’m sure it will make you feel better, even if it won’t get rid of the virus any faster.)
MISCONCEPTION: “Oh, man, I never get colds. My immune system is so good.” Occasionally some obnoxious fool wants to brag about this. Through an implied superiority of diet, exercise, lifestyle, morality, or simple genetics, they claim that they “haven’t had a cold in 10 years! I really feel for you, man. It must suck, getting colds all the time.”
This person is likely full of baloney. If someone “doesn’t get colds,” these are the conclusions you might draw: (1) They are deluded. (2) They have an extremely weak immune system. (3) They completely avoid all human contact.
Let’s back it up and look at the common cold. Basically, this is what happens. The common cold is a virus. There are hundreds of variations on it; the viruses mutate rapidly, and every season brings a fresh crop of new cold viruses that all do more or less the same thing. Because the viruses change so quickly, it’s nigh-impossible for you to have immunity to the common cold; though you may develop immunity to dozens of variations on the cold virus, there will always be a new version to invade you. The virus is most often transmitted through airborne particles: an infected person coughs or sneezes in your vicinity and you inhale a particle or two. It is less often transmitted by hand-to-hand contact. Once a viral particle invades you, it starts replicating. You may have inhaled one copy of the virus, or one thousand. At any rate, the virus starts replicating as fast as it can. At this stage – when the virus is replicating quickly – you are most contagious.
Meanwhile, your immune system is trying to deal with this situation. You have billions of white blood cells of different varieties, which are always circulating through your body checking for infection. Some cells (macrophages) will envelop any kind of invader, deactivating but not destroying them. Other cells are equipped with very specific antigen receptors; they are built to recognize a particular invader, and will react ONLY to that antigen. These B- and T-cells are generated randomly and with an incredible amount of variety – billions and billions are possible. They float around your body looking for a matching invader. Once white blood B- and T-cells that “match” the common cold virus meet and recognize it, they activate and start to clone themselves very rapidly. B-cell clones also produce antibodies which attach to and disable the cold virus. The B-cells keep cloning until the virus attack is under control. Eventually your immune system overcomes the virus completely and you’re cured.
The timeline for this process is usually a few days. The virus enters your body and settles in, starting replication 8-15 hours after initial invasion. Within a few days – although it can be under 24 hours – your immune system catches up and you start to experience symptoms. This short lag is the time it takes for the correct B- and T-cells match up with the cold virus and start replicating. It is this process which actually eliminates the virus. The symptoms, however, are caused by other aspects of your immune system reacting to the invader. It’s somewhat counterintuitive, but a stronger immune system probably leads to stronger symptoms; it’s not the strength of the virus that causes coughing and runny noses, but your own immune response. Your symptoms hit a peak 1-3 days after your immune response begins, and then taper off. The viral load is also tapering off; in the latter days of your cold, you aren’t very contagious, as your immune system has more-or-less taken care of the virus and is just clearing out damaged cells. This is why you’re most contagious before symptoms appear.
Note: Once a specific B- or T-cell has activated in response to a particular virus, it’s stored as a “memory cell” so that if your body is invaded by the same virus again, your immune system already has the right cells in reserve and can respond immediately rather than going through the whole trial-and-error process of running millions of cells against the virus until it hits a match. If the memory cell is available, your immune system can match and stop the virus before it replicates many times, meaning that you never get a very high viral load and you essentially don’t “get” the disease. This is the concept behind vaccination: you’re injected with a small dose of a particular pathogen that has been weakened or killed. Your immune system runs through its “matching” process and once the correct cells “recognize” the pathogen and destroy it, the cell is stored so that the next time you encounter the pathogen, your body can mount an immediate immune response. The pathogen is eliminated before it can reach high enough levels in your body to do damage.
So, back to our “I never get colds” hero. Statistics (trust ‘em or not..) say that the average adult gets 2-4 colds yearly. About 25% of colds are asymptomatic – your B- and T-cells kick in and destroy the virus, but the rest of your immune responses don’t activate. Apparently they’re not necessary to remove the virus. (Our immune system doesn’t always do what’s most convenient for us; just ask people who suffer from allergies.) Anyhow, statistically, it’s highly unlikely that you’re not getting colds. Even if you DO have a very strong immune system, it just means that you might eradicate the virus a bit faster. It’s impossible for you to be immune to the common cold because there are so many variations; you may have immunity to the particular cold virus you caught last year, but this year’s viruses will be different. The only foolproof way to avoid catching colds is simply to avoid human contact! So, the next time someone brags about their superior immunity, hit them back with, “Wow, I feel for you, man – it must suck to have no friends!”
I do realize this post isn’t properly cited, and I apologize, but this is JUST A CASUAL BLOG PLEASE DON’T GET ANGRY AT ME.
The Canadian Medical Association’s Complete Home Medical Guide (2001)
Wrongdiagnosis.com Stats on the Common Cold: http://www.wrongdiagnosis.com/c/cold/stats.htm
Wikipedia’s page on the Common Cold: http://en.wikipedia.org/wiki/Common_cold
Various notes and textbooks from my undergraduate education