Cold vs Flu. There’s a difference between the two.

At some point in the coming months, most of us will start getting the sniffles, the coughing fits, and in general feel miserable. Most of the time it will be nothing more than a cold, but some of us will get the flu. How would you know if you have one or the other, and does it even matter?

Let’s settle this once and for all. Next time you get “sick”, don’t say you have the flu, unless you really know you have the flu. Because, for starters, the cold and the flu are not the same thing. Yes they are both respiratory illnesses, but they are caused by different viruses. The predominant cause of the common cold is by the Rhinovirus (from the Greek, rhinos “of the nose”, and Latin, virus “poison”), whereas the flu is caused by the Influenza A, B or C virus (A and B being the more common severe forms of the virus).

The symptoms you experience with a cold or flu are not only the result of the infection, but they are your body’s immune response to the infection. For example, a high fever is the body’s response to a virus, because a high temperature can inactivate the virus.

As a rule of thumb, the symptoms associated with the flu are more severe. In fact, the flu can be deadly. This is more likely to be the case in children, the elderly, or those who are immunocompromised, all of whom that have a weakened immune system; a prime environment for a virus to thrive in. Both the cold and flu can lead to a runny, stuffy nose, congestion, coughing and a sore throat. But the flu can cause a high fever that can last for several days, along with a headache, fatigue, and general aches and pain. In terms of symptoms, this is where they are different. Colds tend not to have symptoms affecting the whole body, and you can soldier on with a cold, than if you have the flu.

So why is there a vaccine for one and not the other? Brace yourself for Immunology 101 in a way you’ve never seen.

When you’re faced with an infection, you have two arms in your immune system. The innate and adaptive arms. The innate immune response is designed to handle the initial response to a pathogen, and the adaptive immune response is what clears the infection totally. Now, with a viral infection, the adaptive immune response recruits several white blood cells to clear an infection: the key players being T-cells and B-cells.

To explain this bit, I’m going to refer to Lord of the Rings where your immune system is Middle Earth. HURRAH. Now imagine that viruses are like the Orcs, the Uruk Hai that are invading your land. Your T-cells are basically like Aragorn, and have multiple roles: 1) to raise an alarm once they have detected invading viruses (or orcs); 2) kill viruses (or orcs) directly; or 3) help B-cells produce antibodies, ie Legolas firing his arrows. Antibodies are what vaccines are full of. They are synthesised by B-cells as a response to the virus, and bind to the viral particles, in an attempt to neutralise infectivity; basically to stop the virus from multiplying. Once this happens, the T-cells then come along and kill the infected cell. So Legolas (B-cell) fires an arrow (antibodies) which stuns the orc (virus) and then Aragorn (T-cell) comes and saves the day. YAAAAY. And no, Frodo doesn’t get a mention. Because he’s useless. End of Lord of the Rings reference.

Now a small portion of B and T-cells persist and retain an accurate memory of the destroyed virus. Which means, our immune system is primed to prevent another infection from the same virus. Pretty nifty huh? It’s like your body has ammo ready to fire when necessary. HOW AMAZING IS OUR IMMUNE SYSTEM!

But here comes the problem.

Along with viruses being highly contagious, they have the capability to multiply very quickly, and because of this, they have high mutation rates. This means that they can alter the sequence of the viral proteins they express. Much like Mystique from X-Men. HURRAH FOR DC COMIC REFERENCE. Mystique has the mutant ability of metamorphosis, which allows her to be unrecognisable and evade detection. So, if the virus is different enough due to mutation, the antibodies that are required to neutralise them, won’t recognise it, and the virus evades detection by the immune system. Ninja levels 1000.

So what does this all mean? Essentially, we can develop long lasting immunity to a virus that causes us a cold today, but a virus that causes a cold in a few months time, will be somewhat different. And the T-cells and B-cells will have to start from scratch.

This is why there is no vaccine for the common cold caused by the rhinovirus, because there are multiple strains that co-circulate around the world. However there are vaccines for Influenza, because the strains that are likely to dominate each year, are known, and vaccines can be tailored to match them. But once again, as mutations accumulate with future generations of the virus, the virus “drifts”from its parental strain. Which is why a flu vaccine generated for one strain in one year, will prove ineffective for the same flu strain the following year.

The final thing that shall be mentioned, is that antibiotics cannot treat the common cold virus. People think antibiotics are the cure for everything. No. Just no. Antibiotics are prescribed to fight off bacterial infections, and bacterial infections only. And what have I been saying the common cold and flu are caused by? VIRUSES. During a cold, you’re likely to pick up a sore throat, (or strep throat as it is commonly called) which is caused by the bacteria Streptococcus, at the same time as a viral infection. Which is why you are prescribed with them at the time you have a cold. So remember, antibiotics eliminate bacteria. Antibodies assist the clearance of viruses. Best way to remember it is, T in BioTics is for T in BacTeria. Remember that, and you’ll know the difference between the two.

So, whilst the southern hemisphere is enjoying blissful sunshine and warm weather, the northern hemisphere is experiencing the cold and flu season right now. Considering, January just disappeared before our eyes, don’t worry fellow Australians, before you know it, winter is coming. And now you know more about the common cold and flu, than you ever have. Next time someone at work “chucks a sickie”, (which means “use up sick leave” for you northern hemispherians), and say they have the flu, and then rock up to work the next day, either they were lying and went gallivanting, or they didn’t actually have the flu, …they had the cold.

At that point, you catch them. And I say catch THEM. Not their colds.