V is for Virus

I’d planned something else for today, but life intervened as it did last week. In this case, it’s because I’ve come down with the common cold. Naturally, all I’m aware of is this virus, and how it makes me feel.

The common cold is mostly caused by rhinovirus. Among the other types of viruses that can cause the common cold are coronavirus, so-called because of its corona-like ring. This is the same family of viruses that were linked with the SARS outbreak a few years ago.

The common cold is very unpleasant, but for most people it’s not particularly dangerous. Nevertheless, people often wonder why there’s no vaccine, cure or, at least, effective treatment. The short answer is that it’s because it’s a virus.

Viruses are complicated organisms that can replicate only inside a cell. One theory suggests that viruses are left over from evolutionary processes, what biologists call “horizontal gene transfer”. While this can lead to genetic diversity, it more often results in what we call disease.

Vaccines work by creating immunity in the body, that is, the body’s convinced to attack and destroy the infection. To do that, viruses are often killed, so that they can’t produce disease, then injected into a patient to produce immunity. The problem is that viruses can mutate fairly quickly, and some viruses—like the rhinovirus that causes most human colds—has dozens and dozens of serotypes, or, basically, variations in viruses. Immunity to one serotype doesn’t necessarily give immunity to another, so there’d need to be at least 99 different vaccines to protect against the common cold—that sounds like it would be a big injection or a lot of little ones!

Treatment of viruses is also difficult. The drugs used are called “anti-viral”, and there are none that are effective against rhinovirus. In fact, there are very few drugs that are effective against viruses generally.

People often assume that antibiotics will work against a viral infection, but they won’t: Antibiotics only work against bacterial infections (though sometimes anti-fungal medications are called “antibiotic”, too). Bacterial infections can be serious: Bubonic plague, cholera, syphilis, anthrax and leprosy are all caused by bacterial infection. Many upper-respiratory infections are actually bacterial, tuberculosis being the most serious. But all of these diseases usually respond to antibiotics.

Unlike virues.

And that’s why we’ll continue to feel miserable with the common cold for a long time to come: Viruses are difficult to protect against and difficult to treat. In the meantime, pain relief, keeping warm, drinking plenty of fluids and sleeping is about all we can do for the common cold.

Pardon me while I go do that now.

The graphic with this post is of the “molecular surface of the capsid of human rhinovirus 16, one of the viruses which cause the common cold.” It’s available under Creative Commons License from Wikipedia.

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