Ask Emily

29 12 2011

Do cold viruses mutate, or are we simply encountering new viruses with each new infection?

If you’re in situations that expose you to frequent cold viruses, I’ve got some bad news for you. First, what we collectively call the “common cold” is a non-medical way of saying “general upper respiratory infection.” Those sniffles and coughs don’t trace to a single virus or even to a single group of viruses. In fact, more than 200 different viruses can cause what we think of as a cold, and they fall into various classes. The most common is the rhinovirus (rhino refers to the nose). These cause up to 40% of colds. The other two types are coronaviruses and respiratory syncytial virus, which is fairly harmless in healthy people but can be dangerous, particularly for premature infants. Coronaviruses made the news when one turned up as the culprit in the SARS outbreak earlier this decade.

Every time we encounter and do battle with one of these viruses, we develop immunity to that specific microbe. But there are another couple of hundred of them out there, waiting to get into our nasal passages with someone else’s cough or sneeze. In addition, it doesn’t take a lot of viral particles to cause an infection, so trace exposures can still lead to illness.

That’s not even the bad news, though. While people probably muse aloud every time they get the sniffles, wondering why scientists have yet to come up with a cure or a vaccine for the common cold, the fact is, a single vaccine is unlikely. Rhinoviruses, for example, are quite complex and mutate fairly rapidly, evading any immunity we’ve built up to previously encountered strains. In that way, it’s like influenza viruses, which reassort around the globe each year and usually turn up as different strains in each new season.

One thing is certain: You won’t get a cold virus just from being cold. You might be more susceptible to infection if you’re stressed or tired or have allergies.

Some people may think they have the flu, but the difference between an influenza virus infection and a cold virus infection is usually quite stark: a flu infection hits hard and fast, often within hours, with a high fever, extreme fatigue, chills, and possibly gastrointestinal involvement. A cold builds up more slowly, peaking after a few days, and fever is relatively uncommon.

Is there anything you can do to at least ease the symptoms of this incurable but usually benign blight on humanity?  Washing hands is one way to avoid picking up a nasty cold virus, but once symptoms develop, your options are limited. Antibiotics are useless against any viral infection. Vaporizers, fluids, some TLC, and time are your best weapons against riding out infection with any of the viruses that cause the common cold.

And go ahead and resign yourself to the idea that even when you’re over this one, new versions linger out there, waiting to find their way up your nose.

Do you have a question for Emily? Send it to: pkids@pkids.org

By Emily Willingham 


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