We all hear about colds and flu being "bad" for us and how the viruses make us sick but is that really what is happening? Viruses, after all, are not alive like bacteria are, and they simply find hosts that they can replicate in. It's more of what our bodies do in response to viral infections that makes people feel bad when fighting the flu. Let's go through the different parts.
The quick answer is that inflammation caused by our immune systems fighting the viral infection with 3 main chemicals is why our symptoms arise. These symptoms range from a runny nose, sore throat, aches and even green mucus.
The first thing that happens when you inhale or ingest a cold or flu virus is that it will start invading your individual cells, replicate and then rupture those cells to spread more copies of the virus around. This behaviour and having genetic material inside them means viruses are seen as organisms on the edge of life.
But as we have evolved along with viruses, we don't just wait for the viruses to go through all our cells killing us. We mount an immune response as soon as one of our white blood cells encounters a virus. Those first white blood cells that encounter the virus churn out molecules called cytokines in order to draw other white blood cells to the area infected by the virus.
Cytokines also trigger other cells to release bradykinin and prostoglandins which act together in modifying the blood vessels. This is to swell the blood vessels and make them leaky so that white blood cells can more easily migrate though and out to the infected tissue. Once there the white blood cells and T cells literally destroy and mop up the viruses.
So that's the immune response but how do the cold and flu symptoms arise? It's not the virus making them but the symptoms are mainly the effect of those 3 main molecules named above, cytokines, bradykinin and prostoglandins on the body.
When healthy volunteers are administered a dose of cytokines in research, they develop symptoms of colds and flu from fever to headaches. The fever comes about due to exposure of cytokines to some of the nerve endings that communicate with the temperature control centre of your brain. This part of the brain is called the hypothalamus and you can think of one of its functions as being a thermostat. The cytokines would be the finger pushing the set temperature up to fever amounts. Read more about why fever is good for you.
Also while not fully understood, cytokines seem to be producing the chills, loss of appetite and aches in your body as well. So the general unwell sensations and signs of viral infection are due to cytokines and not directly by the virus, our immune system releases more cytokines as part of fighting the virus.
Bradykinin and Prostaglandins
As described before, bradykinin and prostoglandins are part of the inflammation process bring more of your immune cells to the infected area. As most viruses are inhaled or ingested, the nose and throat are some of the first areas affected.
The scratchy throat, going from a tickle to a painful throat is the effect of bradykinin and prostoglandins on the nerve endings for pain in the throat.
The sneezing is due to the same molecules triggering the sensory nerves in your upper throat and nose that go to the brain's sneeze centre. Please note that it is another molecule, histamine, responsible for the sneezing associated with allergies.
The coughing is also an excitation of different nerve endings below the throat, in the airways.
The blocked nose comes about as bradykinin and prostoglandins dilate blood vessels and so the swelling of veins in your nose eventually leads to the sense of being blocked.
As too, the watery eyes are coming from blocking of tear ducts with the same type of swelling.
So if you realise by now, the symptoms of colds and flu is more about what your body is doing to purge itself of an intruder, not the virus itself causing you trouble. Just like vomiting can be a very unpleasant experience but when it is clearing bad food out of your stomach, it's a worthy process. So you would be wise to strengthen your body and your immune system so that it can withstand the inflammatory process easily and if your immune system is functioning well it can combat the virus rapidly and effectively for less trouble and time out than other people. But what about the green mucus?
This is a green coloured protein found in some infection fighting white blood cells. During the early stages of inflammation in the nasal mucosa, the discharge is clear to white. As more white blood cells come to fight the viral infection the increased amount of myeloperoxidase makes the discharge go from white to yellow and eventually green when there is sufficient amounts of it. This is the same as the mucus you cough up as well.
The idea that green mucus means bacterial infection is wrong.
So with this understanding of colds and flu symptoms you should be less wanting to say how bad virus are and more how amazing your body is in what it can do. In chiropractic we see a lot of the problems people having as a disruption of normal mechanisms in their body leading to symptoms rather than just a medical term being cursed onto them. In this case we can see the body defend itself and as part of that it is purging itself as well as making you seek rest so it can focus on recovery and reduce spread of infection.