The Most Successful Pathogen
Looking at disease from the POV of the microorganism
During my years studying microbiology, a professor once said,
“The most successful pathogen is one that doesn’t kill its host”.
Let’s pick apart this statement.
A pathogen is a microorganism that infects a ‘host’ and causes illness. So, what does a ‘successful pathogen’ mean? Let’s look at it from the microorganism’s point of view. Without a host, most deadly pathogens—especially viruses—can’t stay alive for too long. So, they need to effectively infect the cells of an organism – the ‘host’. The microorganisms’ main goal is to infect a host cell so that it can reproduce. Viruses can’t reproduce or multiply on their own; they need to use the proteins, enzymes, and other machinery of the host cell. When they do this, the host becomes ill, and their immune system starts working to destroy the pathogen. What happens if the host becomes too ill and dies? Any pathogens inside the host would die with it because it’s not mature enough to move out into the environment. The pathogen has successfully reproduced only if the newly formed pathogen cells become mature enough to be released from the host and infect a new one. The host should be healthy enough to allow full maturity of the microorganism, but the microorganism should also be strong enough to withstand the host’s immune system.
Think about the CoVID19 pandemic. It was devastating, and many people died. But eventually it was brought under control. The newer variants of the CoVID19 virus became less deadly to us hosts; not because we became stronger, but because the virus tried to become a better pathogen. Of course, the vaccines helped to bring it under control as well. If a virus is too deadly, it doesn’t get enough time to evolve and mutate to form too many new variants, and so, the vaccines work quickly in bringing it under control.
Let’s talk about another example – the seasonal flu. It’s not a deadly disease, but it recurs again and again. Every year, millions of people around the world fall sick with the common cold whenever there’s a change of season. However, almost every one of these people recover as well. If you’re a healthy individual, a flu infection wouldn’t kill you. What is happening? It’s simply this – the pathogen successfully reproduces and completes its life cycle to maturity, and the newly produced mature microorganisms exit the host successfully without making the host too ill. The host recovers and becomes healthy again. By the time the next flu season comes around, the pathogen changes itself enough to evade the immune system and infect the healthy host again!