What is the biological purpose of sexually transmitted diseases?

STDs serve the organisms that cause the disease.

To be effective as a species, any organism has to find food, mate, reproduce, and spread itself (or it’s children) to new sources of food. A lot of organisms use our bodies for food and reproduction. There are different ways they transmit themselves outside of our bodies. The problem (for the organism) is that the environment outside our bodies is not very conducive to transmission. Air and water borne organisms have to harden themselves. Sexually transmitted organisms are actually body-fluid transmitted. It just so happens that humans don’t usually exchange body fluids unless they have sex, so these diseases are called Sexually Transmitted Diseases. STDs can be passed by blood transfusion and from mother to child during birth. The sexually transmitted organisms have merely figured out that they don’t need to harden themselves against the environment if they are transmitted sexually.

The question remains: Why do these organisms cause disease? Isn’t it illogical that they kill or reduce the health of the host? It reduces the chances that they can transmit themselves. Yes, that is a very good question. And most organisms in our bodies don’t kill us or cause disease. Many of them are sexually transmitted. The vast majority of organisms in our bodies are either beneficial or don’t do any harm. It’s only when the organism causes harm do we start worrying about it. For the most part, organisms do not kill the host. The number of organisms that cause disease are the minority.

But, even so, why do these minority of organisms cause disease? It’s because they can’t help it. Disease really is a side effect of something else that the organism uses us for. HIV, for example, cannot reproduce on it’s own. It reproduces by hijacking some of our white blood cells. The side effect is that this kills our immunity, and then our body cannot fight all the other diseases. HIV isn’t trying to kill us. Its trying to reproduce. The death of the host is a side effect that HIV doesn’t care about because it has already reproduced.

Source: Here

Author: Jayesh Lalwani (GQA gold writer)