Too many viruses, too few ‘cures’ for the common cold

February 2003

Got a cold? Well, here’s some good news for you: there’s a strong possibility you’ll never get the same virus that caused your cold again.

The bad news is, just as your body has primed itself to avoid getting that particular virus again, there are more than 200 other viruses circling around to take its place.

That — in a nutshell — is precisely the reason why it is so difficult to find a cure for the common cold. Just as the body has a difficult time warding off viruses circulating in the air, researchers are having an equally difficult time finding a medication that targets all of those illnesses.

“The key thing is we’re not dealing with a single virus here,” said Ronald Eccles, PhD, director of the Common Cold Centre at Cardiff University in Wales. “If it was something like smallpox, we would have had a cure for it years ago.”

Causes of the cold

According to estimates from the National Institute of Allergy and Infectious Diseases (NIAID), rhinoviruses are believed to cause most adult colds, from 30% to 35%, with coronaviruses coming in second. The importance of coronaviruses as causative agents is hard to assess, because unlike rhinoviruses they are difficult to grow in the laboratory. NIAID estimates 10% to 15% of adult colds are caused by viruses also responsible for other, more severe illnesses: such as adenoviruses, coxsackieviruses, echoviruses, orthomyxoviruses (including influenza A and B viruses), paramyxoviruses (including several parainfluenza viruses), respiratory syncytial virus and enteroviruses. The causative agents behind the rest of the common colds, unfortunately, remain unidentified.

NIAID did not have figures on the viruses that commonly cause colds in children.

Options for treatment

So, with all those viruses out there, what are the options for treatment?

Most physicians agree that symptomatic treatment for symptoms of the cold is the best therapy.

Last summer, the FDA rejected the drug pleconaril (Picovir, ViroPharma), which targeted one cause of the common cold, the picornavirus, after an advisory panel unanimously voted against the drug’s approval. The panel expressed concerns that the medicine might cause serious adverse events, including disrupting the menstrual cycles of women taking oral contraceptives.

The advisory panel also expressed concern that drug-resistant strains of viruses had appeared during company-sponsored studies and that their spread was a factor if the drug was in widespread use.

While the FDA advisers did agree that the drug was effective in reducing the length of a cold by about a day, it concluded that its benefits did not outweigh its risks.

“You can see the way common cold medications have a big hurdle to jump over, if they’re going to be in general use. We’re dealing with a mild illness, therefore, these agencies are not going to tolerate any side effects or any risk,” Eccles said. “Even simple aspirin has risks and side effects, it’s obviously a big hurdle for the drug companies to get over.”

As with the development of a targeted medication, the development of a vaccine that could prevent the common cold has reached an impasse due to the expanse of different cold viruses. Each virus carries its own specific antigens, substances that induce the formation of specific protective proteins (antibodies) produced by the body. Until methods are found to combine many viral antigens in one vaccine, or to take advantage of the antigenic cross-relationships that exist, prospects for a vaccine are dim. According to Eccles, evidence that changes occur in common-cold virus antigens further complicate development of a vaccine.

So, with no other drugs or vaccines specifically to treat the common cold in sight, what are the options for treating the common cold? Eccles said the first step is prevention, by eating properly, exercising and washing hands and surfaces that may come into contact with germs. However, if you already have a cold, a trip to the pharmacy and drinking lots of fluids are still the best options.

If a person’s predominant symptoms are runny nose and cough, he said, the first-generation antihistamines have some benefits. The issue in administering these over-the-counter medications is the consideration of a child’s reaction to it. Many antihistamines have sedative properties, which may be beneficial to the child at nighttime, but could make them drowsy during the day and inhibit their school work.

For nasal congestion, topical decongestants like nose drops are generally effective.

Headaches and sore throats require analgesics and are generally effective in easing those symptoms, but patients should be warned of the dangers of multi-component medications.

Avoiding unnecessary medication also applies to antibiotics, which often get prescribed when children have ear symptoms — even though ear symptoms can accompany common respiratory infections and are probably not caused by bacteria.

Eccles also said he advocates the older homespun remedies, like eating soup and using honey and lemon, because they stimulate salivation, which in turn stimulates mucus production and thus helps to fight the virus and also provide symptomatic relief for cough and sore throat.

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• Dr. Eccles has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.