Pique the Geek 20100214: The “Common” Cold

Well, I am back now.  I had planned to provide an installment last week, but I had a bad cold and just did not feel much like setting at the keyboard.

Personally, I do not mind the coughing nor the sneezing, or even the sore throat.  The one thing that bothers me the worst is to lose my ability to thermocompensate, such that I feel either cold or hot when I should be in my comfort zone of temperature.  Aspirin assists me to regulate a bit better, but being well is the better feeling.

No one knows how long the common cold has been with us humans.  There are literature references from antiquity, so this is not anything new.  We do know that a virus is responsible for it, specifically a rhinovirus, and there are many of them.  Without getting too technical, there are many different ones, and they all have different signatures on their protein coats.  I must have picked one up for which my immune system had no primer.  In addition, some colds are caused by a conronavirus.

Interestingly, both of these types of virus are retroviruses, meaning that their genetic information is encoded with single strand RNA rather than double strand DNA.  HIV is another a retrovirus, but infection with it has much more grave consequences, since the HIV virus causes AIDS.  Interestingly, the rhinovirus is one of the smallest RNA viruses, whilst the coronavirisus are some of the largest.  Go figure.

UPDATE:  Commenter ebohlman points out to me, correctly, that not all RNA viruses are retroviruses.  He or she points out that “typical” RNA viruses like the ones that cause the cold merely hijack the cellular metabolism over to produce more of their own RNA without going into too many more steps.  Retroviruses, on the other hand, transcribe their RNA into your cells’ DNA and then express it.  This is a significant difference, and I apologize for being incorrect.  By the way, the process of transcription of the viral RNA to your DNA requires an enzyme called, sure enough, reverse transcriptase, and it this enzyme is blocked the retrovirus can not reproduce.  This is one of the approaches that several of the modern anti-HIV drugs use.  Once again, thanks to Kossack ebohlman for calling my attention to an error.

There are differences in behavior between the two kinds of viruses.  Rhinoviruses tend to reproduce more quickly at temperatures a little below body temperature, so this is why they almost exclusively cause upper respiratory infections (the nasal lining is cooler than body temperature because of cool atmospheres and evaporative cooling.  My guess is that colds are more frequent in the winter partly because the dry winter air causes the nasal lining not only to dry out, but to stay cooler because of evaporation.  If this hypothesis be correct, then running a humidifier should help to reduce the frequency of colds, and it does seem to be the case for me.  Coronaviruses are not so limited, and can cause lower respiratory infections, including the deadly SARS outbreak a couple of years ago.  They also cause some rather serious gastrointestional infections as well.

For the most part, you can not get the same cold more than once.  Your immune system makes you, well, immune, after you get a specific infection.  Thus, if you have worked with food or other intimate things when you have a cold, those will not reinfect you since, after you get well, you are immune to that specific serotype of virus (there are hundreds of rhinovirus serotypes), so it is fine to freeze that leftover food and eat it later.  However, since there are so many serotypes, it is unlikely that you would ever be infected by all of them, so there are varieties to which you have no immunity.  This is thought the be the main reason that children gets colds much more often than older folks; they have not been exposed to very many common serotypes, so are susceptable to many more than geezers like I am.   Just do not take food items to to your neighbors, because they might not be immune to your strain, so be kind to them.

Now, that rinovirus is clever, even though not really even living, and mutates from time to time, so that is why we still get colds.  A mark of a successful disease is that it only infects it host for a while, reproduces, and then goes away for a bit.  The most successful germs do not kill their hosts, or have such a long incubation period before a full blown, fatal disease develops, like AIDS, giving the virus ample opportunity to infect other hosts before the first host expires.

The incubation period for the rhinovirus is extremely short.  It begins to bind to the receptor in the nasal cavity within 15 minutes of introduction, and symptoms can be felt, in some cases, in as little as under a day, and almost always within four days or so.  Two days is typical.  There is not really a whole lot that you can do once you are infected.  Some studies suggest that zinc preparations can reduce the binding of the rhinovirus to the receptor in the nasal passages to which it binds, but they are not conclusive.  Vitamin C is also suggested as a preventative, but the studies regarding it are inconclusive as well.  I will say that if you are deficient in either of those essential nutrients, you are more likely to catch a cold because your immune system is not at its best, but that is a far cry from saying that either of those materials definitely has a specific beneficial effect beyond good nutritional value.

Having stated that, I will point out the I regularly take extra zinc and Vitamin C, along with a multivitamin and extra D, not s much to prevent colds but rather to make up so some extent for a diet that is not quite as good as it should be.  One product that is heavily promoted is Zicam, mainly zinc gluconate and some homeopathic extras.  There is no evidence that these types of products reduce the duration or severity of a cold, regardless of what Rush Limbaugh says.  The FDA actually forced Matrixx Initiatives, the company that owns Zicam, to remove several of their nasal swab products from the market a couple of years ago because of a rather alarming association between use of the nasal swabs and the irreversible loss of sense of smell.  It might not sound like a big deal, but in addition to the lack of sensory enjoyment of food and drink, having no sense of smell can actually be quite dangerous (for example, you would have no way to know about a natural gas leak).  In my opinion, a cheap generic zinc supplement is as good as branded products

The best was to deal with a cold it to avoid getting one, and the best way to do that is avoid people who have one.  That is more easily said than done, but recent studies seem to indicate that the majority of colds are caused by self inoculation after touching contaminated surfaces.  You touch something with the virus on it, then rub your nose or eyes, and you get infected.  Thus, there is real value in frequent hand washing, the use of hand sanitizer, and trying not to rub your nose and eyes.  I am pretty sure that I caught my cold from a contaminated shopping cart handle at the store, and will take extra precautions in future.  As a matter of fact, they have begun to sanitize the cart handles at Wal-Mart, at least here in the Bluegrass.  By the way, do NOT shake hands with people if you have or think that you are getting a cold.  Simply explain the situation and I would be shocked if anyone would be offended.

Once you get a cold, you pretty much just have to put up with it.  There are lots of OTC remedies that make the symptoms less aggravating, but note that many of them contain acetaminophen, which consider to be a very dangerous drug.  If you can tolerate aspirin, I recommend it.  Ibuprofen is also a good choice.  If I take aspirin to reduce the low grade fever, I am much more comfortable and can live with the other symptoms.  Lots of hot drinks are good, too.  The old standby, chicken soup, if not improving the disease outcome, at least opens up your nose and provides excellent nutrition.

There are a couple of antiviral drugs that work on the rhinoviruses, but it is almost never wise to use powerful drugs for a condition that is rarely life-threatening (in some folks with asthma there might be a reason to reconsider).  Antibiotics have no effect at all on a cold, but may be of value if a bacterial secondary infection develops, but this is quite rare.

There may be the possibility of a vaccine in future for a wide range of serotypes of the rhinoviruses, since one particular protein is strongly conserved over them.  However, I would not hold my breath, because our native immune system does not recognize that protein very well or we all would only have one cold, ever.  On the other hand, there are some techniques that can be used to boost the immune response to vaccines, so it may be possible.

Well, you have done it again.  You have wastes a perfectly good batch of photons reading this rubbish.  Even though Rush Limbaugh swears off Zicam when he reads me say it, I always learn much more than I could possibly hope to teach writing this series, so keep those comments, questions, corrections, and other thoughts coming, regardless where you choose to insert them in the comments.

Warmest regards,

Doc

Crossposted at Daily Kos