Why Is It So Hard To Cure The Common Cold

The Challenge of Treating the Common Cold

In 2000, ViroPharma, a pharmaceutical company, conducted clinical trials for pleconaril, a new pill designed to treat the common cold. While the pill proved effective for many patients, seven of them developed mutated virus variants that were almost completely resistant to pleconaril just a few days into the treatment. This rapid mutation outmaneuvered years of research and development, highlighting the challenges of treating viral infections.

Without an immune system, a cold infection could quickly spread deep into the lungs, leading to tissue destruction and eventual asphyxiation due to insufficient oxygen supply. This is a real risk for millions of people worldwide living with a less-than-fully-functional immune system or those on immunosuppressant drugs. However, for those with a fully functional immune system, a cold usually results in relatively mild symptoms.

The Complexity of the Common Cold

On average, adults catch more than 150 colds throughout their lives. Despite similar symptoms, the cause could be different each time. Common colds are caused by at least eight different families of viruses, each with its own species and subtypes. These viruses invade our bodies in a few ways, one of which is through the air we breathe. Our immune system sets up frontline defenses that produce many of the symptoms of a cold, such as a runny nose, fever, and inflammation.

Is a Cure for the Common Cold Possible?

Given that the common cold is caused by many different viruses, finding a cure is challenging. However, one fact in our favor is that a single family of viruses, rhinovirus, causes 30 to 50% of all colds. If we could eliminate all rhinovirus infections, we’d go a long way towards curing the common cold. There are two main ways to fight a virus: vaccines and antiviral drugs.

The Challenges of Vaccines and Antiviral Drugs

The first attempt to create a rhinovirus vaccine in 1957 was a short-lived success. William Price vaccinated 50 kids with inactivated rhinovirus and gave 50 others a placebo. A rhinovirus outbreak soon followed, and only three kids in the vaccinated group got sick compared to 23 in the placebo group. However, later trials of the vaccine showed no protection at all due to the multiple subtypes of rhinovirus.

Creating antiviral drugs is also challenging because viruses hijack human cellular machinery to replicate and spread. It’s hard to make a molecule that’s toxic to the virus without also being toxic to the human. Even if this is achieved, the virus could mutate out of reach of the drug.

Hope for the Future

Despite these challenges, there have been some incredible successes. Smallpox was eradicated thanks to an effective vaccine, the fact that it can’t hide out in other species, and its relatively low mutation rate. HIV, which mutates quickly, can be managed with an effective cocktail of drugs that the virus can’t easily mutate away from.

While we are stuck with colds for now, the last few decades have featured some entirely game-changing medical breakthroughs, like mRNA vaccines and CRISPR. CRISPR, which originally evolved in bacteria as an immune defense against viruses, could be particularly promising as an antiviral agent. Early in the COVID-19 pandemic, a research team showed that a CRISPR system could degrade coronavirus and influenza genomes in our lung cells. They called their system prophylactic antiviral CRISPR in human cells, or PAC-MAN for short.