What are mutations of diseases?

OK… most diseases are caused by viruses and by bacteria.

Those viruses and bacteria proliferate inside the body. They reproduce. Now in every reproduction, there is a possibility that the genes aren’t copied exactly from the parent organism. But they “mutate”, that is, become different. Many mutant organisms will be weaker than the parent organism. But a few will be stronger. Or more fit to survive and reproduce.

If that happens and the mutant virus or mutant bacteria reproduces a lot, there will be a new breed of viruses/bacteria. It might be more contagious that the original. Or more resistant to antibiotics. Or just different in its surface structure. Often, the medicaments that are known to cure a disease will fail to cure the mutant of a disease.

There’s one of the dangers of overusing /wrongly using antibiotics… You have a patient with a bacterial infection (that can be cured with antibiotics). The patient gets antibiotics. But doesn’t take them long enough. So the antibiotics kill all the bacteria that are easy to kill. And then the more resistant ones survive. But they are few. But as the patient feels healthy, he stops taking the meds. Now the resistant bacteria have a lot of space to reproduce. And they do. After that the patient has a fall-back with the same disease, but the antibiotics will not help at all. The same happens when unnecessarily overusing disinfection agents. The tough germs survive and come back later. And bring their family.

Diseases that have other causes than living things (for example auto-immune diseases, metabolism disease and malnutrition diseases) do not have mutant forms.