Infection is the process and result of the introduction of foreign agents into the body. Usually distinguish lesions by viruses, fungi, protozoa, bacteria. Lately, mysterious prions have also been added to these categories of pathogens, but we will leave them for dessert in a story about pathogenic agents.
Let us consider in more detail the various pathogens that cause infectious diseases.
Not really life
Viruses are unique creatures because not all biologists agree to call them living beings. They are so strange. They are DNA (RNA) in a protein “coat”, very small and ubiquitous. A genome can be just a couple of genes, or it can contain a couple of hundred of these elements of heredity. Sometimes the protein coat is covered with another, in which the proteins of the host organism are involved. For example, infectious diseases such as influenza are caused by conspiratorial viruses.
Primitive plants
Everyone who has ever experienced mycosis of the foot or thrush, can assume that they met with "bad fungi." Most fungi live in the body peacefully and do not interfere with the host. Although there are pathogens. But the thrush - normal fungi that got out of control. Usually they are slightly suppressed by vaginal lactobacilli, therefore, an infectious disease of thrush occurs when the population of natural lactobacilli is reduced or the immune system worsens. So you should not use soap when washing, and also drink antibiotics unnecessarily.
Difficult diseases
Sometimes the disease is caused by organisms called protozoa. They cause such serious infectious diseases as malaria, dysentery and African sleeping sickness. Biologists do not like the name "protozoa", but doctors are conservative in their classifications.
Asexual creatures
Bacteria are prokaryotic creatures. They do not have a pronounced core, and this distinguishes them from the simplest. Propagated by division. Evolutionarily unpromising, but very reliable. Infectious diseases caused by bacteria, a person has learned to treat best. At least, these pathogens, unlike viruses, could be seen through a not-so-powerful microscope.
The punishment of cannibals
Prions are strange proteins that themselves cause disease, live in the brain. Similar to viruses, only without nucleic acids. Especially common in New Guinea, where people have a cute custom to eat the brain of the dead. So, most Europeans are not threatened with the disease, unless they want exoticism. For the same reason, it is better not to eat a livestock brain, even if they try to convince you that at least once in your life you should definitely try a “delicacy”.
What to do?
Now you know what causes the disease. The treatment of infectious diseases, of course, depends on the type of pathogen. Good old antibiotics will only help against bacteria. Fungi are treated with special drugs like fluconazole, and they also try to restore the normal bacterial background of the body so that beneficial bacteria keep pathogens in check. Viruses are treated with special antiviral drugs that target a specific virus, as well as immune stimulants. Better than immunity, nothing can destroy viruses. The only exception is HIV. But many viral infectious diseases we have learned to win. Protozoa are destroyed by various chemicals, which were sometimes found by chance. Infectious disease provoked by prion is almost always a sentence. We still know too little about these pathogens, even their nature is not completely clear.
Reminders of the need for hygiene have already snapped everyone’s teeth, but we have to admit that it was increased hygiene measures that saved mankind from repeating epidemics of terrible diseases that “mowed” people in the Middle Ages. So washing your hands once again is not out of place. Well, it's better not to try brains ...