New Study Shows that the Common Cold combats Influenza

Recently, a team of Yale researchers tested the theory that rhinovirus, the most frequent cause of the common cold, can help prevent influenza infections. The team led by Dr. Ellen Foxman, an assistant professor of laboratory medicine and immunobiology at the Yale School of Medicine, concluded the three-year study earlier this month. But before we get to the findings of their research, it's important to distinguish between the common cold and the flu.

Some people might not realize that there is a difference between the cold and the flu, but this couldn’t be further from the truth. The flu is caused by the influenza virus, while the common cold is most often caused by the rhinovirus. The easiest way to tell the two apart is from their symptoms, as shown below in a helpful table made by the CDC:

As you can see, the common cold & the flu are remarkably similar, and cause many of the same symptoms. In general, the common cold can be described as a milder version of the flu. So, you might be thinking to yourself “Then how exactly are they different?”

Firstly, the flu has a more rapid “symptom onset”, meaning you will notice the symptoms appearing more suddenly than with the cold. And while they may both cause coughs, the type of coughs they cause are different. The flu causes a severe, dry cough, which are rarely caused by the cold. The cold typically produces a wet cough, which is the type of cough that brings mucus to your mouth. Another symptom shared by both is a fever. However, the fever caused by the cold is a “low-grade fever”, which means the temperature is lower than 38°C. The flu, on the other hand, causes a fever is greater than 38°C, which is much more severe. Finally, the flu is commonly associated with muscle aches and headaches. These are exceedingly rare in cases of the common cold.

Now that you understand the difference between these two illnesses, we can return to the study. The study analyzed the medical history of nearly 14,000 patients. The data showed that where the rhinovirus was present, the influenza virus was not. The team also experimented with respiratory tissue. Some of the respiratory tissue was infected with the rhinovirus, while the rest was given a “mock” infection (meaning no actual infection took place) as a control group. The picture below shows the comparison between the two after being infected with influenza.

As you can see, on the left, the bright green spots (indicating influenza) are much more prevalent than on the right. This evidence shows that the rhinovirus does prevent influenza infections. But why?

When you are infected with rhinovirus, it jumpstarts the immune system before the influenza enters the body. Think of it this way: your body is a house. The way your body deals with invaders is by lighting the house on fire, killing the invader. Now imagine the rhinovirus comes along; this causes your body to light the house on fire. If influenza attempts to infect you, the house is already on fire. This causes the influenza to die before it can spread, and thus, no flu.

One highly relevant question is: “Can this help prevent the spread of COVID-19?” And the answer is… We simply don’t know. When asked, Dr. Foxman responded with “It is impossible to predict how two viruses will interact without doing the research”. And so, it seems that, for now, we’ll just have to settle with masks, hand sanitizer, and staying at home.

Stay safe everyone.