I mean common cold has been around for a long time. How has the immune system not learned how to fight it?
In: Biology
Three main reasons.
One:Just as our immune systems are evolving to fight diseases better, diseases evolve to avoid the immune system better. One of the most tenacious things about the common cold is that viruses of that type can evolve very quickly to avoid being destroyed by our immune system. This also makes it very difficult if not impossible to design a vaccine against them.
Two: We have enough humans globally interconnected enough that diseases can continue finding humans that haven’t experienced the disease(and begun developing immune defenses) yet for a LONG time. Imagine how long it would take for a cold that started in south America to travel and infect people in Mongolia.
Three: your immune system doesn’t remember diseases forever. It depends on a lot of factors but you can be reinfected with a strain of cold that you’ve experienced before several years after your infection.
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