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?

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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.

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.

Herpes just chills arround until the host is to weak to hide it. They you will see an outbreak.