Overview of Human Disease

There are many types of human diseases caused by a variety of internal and external issues. There are really only two types of diseases affecting humans:

• External: where something outside the body causes a disease, like a virus, bacteria, or other microbe. or poisonous toxin.
• Internal: where something goes wrong with an internal body system, like in genetic diseases.

Much of the arguments about various diseases are over whether a particular disease is caused unnaturally from the external environment, versus naturally by some internal mistake. For example, are cancers caused by a virus, or do they occur naturally by the normal process of DNA mutation that occurs in every person? In the case of cancers, it is far from clear, but certainly there is some internal aspect from over-reproduction, which is perhaps triggered initially by external agents.

There are a variety of clearly "external agents" that cause damage or diseases:

• Bacteria: single-celled creatures
• Viruses: not even a full single cell, but small entities that actually live within our own body cells.
• Single-cell parasites: protozoa, filaria, richettsias and spirochettes.
• Multi-cell parasites: worms, flukes, insects, fungi, yeasts
• Malnutrition disorders: inadequate diet leads to various disorders such as vitamin deficiencies and mineral deficiencies.
• Toxins: chemicals, poisons and pollutions that damage the body cells
• Radiation: cell damage from sunlight, nuclear, electromagnetic and other energies.
• Physical damage: the situation where some physical activity or event causes a condition, such as accidents, homicides, and so on.

The other class is disease arising from an internal failing of the body's system. Although perhaps some are triggered by an external environmental cause, they all end up with the body acting improperly, somehow getting into the wrong mode. There are a variety of common types of "internal problems" that lead to diseases:

• Inherited genetic defects: diseases that are already programmed into the body at birth, leading to genetic diseases.
• Cancers: mutated body cells that grow too quickly, creating clumps of cells called tumors.
• Leukemias: a particular type of cancer.
• Immune response disorders: an overactive immune system leads to various problems such as allergies and asthma.
• Autoimmunity: a severe immune-response disorder where good cells are mistakenly killed by our own immune system
• Metabolic disorders: disorders of the control of the body's energy metabolism (e.g. Type 2 diabetes).
• Prions: where "bad" proteins somehow over-replicate like viruses
• Mitochondrial disorders: rare type of genetic diseases that affect the cell's power plant called the "mitochondria".
• Anatomical problems: where some part of the body's structure creates an obstruction or internal problem, such as birth defects.