Hundreds of different diseases exist. Each has its own particular set of symptoms and signs, clues that enable a physician to diagnose the problem. A symptom is something a patient can detect, such as fever, bleeding or pain. A sign is something a doctor can detect, such as a swollen blood vessel or an enlarged internal body organ.
Every disease has a cause, although the causes of some remain to be discovered. Every disease also displays a cycle of onset, or beginning, course, or time span of affliction, and end, when it disappears or it partially disables or kills its victim.
i. An epidemic disease is one that strikes many persons in a community.
ii. When it strikes the same region year after year it is an endemic disease.
iii. An acute disease has a quick onset and runs a short course. For example an acute heart attacks.
iv. A chronic disease has slow onset and runs sometimes for year. The gradual onset and long course of TB makes it a chronic ailment.
On the basis of their occurrence diseases are of two types: – congenital and acquired disease. Congenital diseases are inborn diseases present from the birth & which are generally inheritable. These diseases occur due to gene or chromosomal mutations, e.g. Colour blindness, thalassemia etc. Detailed study is given in human genetics chapter.
Acquired diseases which are caused by pathogens from infected persons to healthy one are infectious diseases. These occur only after birth & are non-inheritable. Acquired diseases are of two types –
Communicable diseases (Infectious) are those that can be passed among persons such as by means of airborne droplets from a cough or sneeze. Tiny organisms such as bacteria and fungi can produce infectious diseases.
So can viruses. So can tiny worms. Whatever the causative agent might be, it survives in the person it infects and is passed on to another or its eggs are passed on.
Sometimes, a disease-producing organism gets into a person who shows no symptoms of the disease. The symptomatic carrier can then pass the disease on to someone else without even knowing he has it.
Non-communicable diseases (Non-infectious) are caused by malfunctions of the body. These include organ or tissue degeneration, erratic cell growth, and faulty blood formation and flow. Also included are disturbances of the stomach and intestine, the endocrine system, and the urinary and reproductive systems.
Some diseases can be caused by diet deficiencies, lapses in the body’s defense system, or a poorly operating nervous system. Advances in medical science make it possible to prevent and treat many diseases that once caused death.