Eli5 if disease’s want to live in a host’s body without being discovered, then why do they have such nasty symptoms that can be used to easily identify and destroy them?
In: 106
Everything needs to replicate and spread to survive so something that causes sneezing and coughing is helping itself spread to new hosts.
Some symptoms of disease and illness are actually not caused by the sickness itself but rather our immune system trying to fight it off.
Also remember diseases don’t “want” anything and they don’t make any decisions as to how to affect the host. The diseases that spread around are just the ones that happened to have or develop features over the years that make them infectious in one way or another. Could be they happen to cause sneezing or coughing in the host, which helps them spread to other hosts. They didn’t make a plan or get designed to do this, it’s just how it turned out based on the environment.
Herpes just chills arround until the host is to weak to hide it. They you will see an outbreak.
It depends a lot on the disease. Many of the nastiest diseases aren’t supposed to be in humans at all. All strains of influenza originally come from birds, where they cause almost no symptoms and live perfectly happily alongside each other. However when they cross into a species they are not evolved for, such as humans, they cause problems, as the mechanisms they evolved to replicate without problems for the host don’t work properly in humans.
This is the case for many (but not all) of the nastiest diseases, Ebola, Covid, etc, which come from bats and cause no symptoms in their original host, as well as HIV, which originated in chimpanzees.
Humans do have many bacteria and viruses that do live inside them and cause no problems at all in most cases. CMV and EBV are common viruses that cause zero symptoms in most people, but sometimes cause bad reactions in those who are immune deficient. Most cases of meningitis are caused by bacteria that live inside the noses of 80% of people perfectly happily, and only rarely decide to cross into the blood and cause problems.
Then you have diseases like colds, which are evolved for humans and cause only mild symptoms, but make you sneeze and cough, allowing you to spread the virus much further and to more hosts than you would normally
The human body is also full of all sorts of other bacteria and viruses that help us in many ways, and could be called the most effective ones to co evolve with us.
Our bodies cause the symptoms. Not the virus directly. Your immune system is trying to eliminate a “contaminate.”
Think about how you can also get a runny nose from pollen that isn’t a threat. Your body only thinks it is, and creates the symptoms.
it triggers a lot of symptoms that are used to spread itself. sneezing, coughing etc. body fluids everywhere. theyre bloody clever. it doesnt benefit a virus to kill its host. the run-down feeling is our body diverting resources to fight it
First, the goal of every disease to spread, to “procreate”. They are mindless and while the disceory chance increases, if it increases the transmission and successful spread more, than the loss due to discovery and immune response, it is a positive change.
Just laying dormant in the body having a low reproductive rate and hiding, is worse than making the host ache and sneeze and vomit. Eventually the hidden organisms either die off or got destroyed anyway.
—
Second, many most obvious symptoms are caused by your immune system and reflexes, rather than the “pathogen”. Fever, coughing, sneezing, increased mucus production
—
Third, survival of the fittest… the version that could spread and multiply wins… again, lying dormant doesn’t work, just in extreme cases
Symptoms are an indication of the fact that your immune system is fighting the infection/disease. They are caused by the immune system, not the sickness itself.
The second part of your question is kind of muddled up, as others have explained.
But at a more basic level, if a microorganism doesn’t create nasty symptoms, then it’s not a disease.
Countless harmless or beneficial microorganisms do just fine by living inside or on the skin of humans and spreading through casual contact.
Latest Answers