A disease is a condition that impairs the proper functioning of the body or one of its parts. Every living thing, both plants, and animals can succumb to the disease. People, for example, are often infected by bacteria. But bacteria, in turn, can be infected by viruses. Hundreds of different diseases exist. Each has its own particular set of symptoms, signs, and 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 partially disables or kills its victim.
* An epidemic disease strikes many persons in a community. When it strikes the same region year after year, it is an endemic disease.
* An acute disease has a quick onset and runs a short course. For example, an acute heart attack. A chronic disease has a slow onset and sometimes runs for years. The gradual onset and long course of TB make it a chronic ailment.
Based on their occurrence, diseases are of two types congenital and acquired disease. Congenital diseases are inborn diseases present from birth & which are generally inheritable. These diseases occur due to gene or chromosomal mutations. e.g., color blindness, thalassemia, etc. A detailed study is given in the human genetics chapter.
Acquired disease 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) can be passed among persons, such as using 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 the stomach and intestine disturbances, 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 dean.
SEXUALLY TRANSMITTED DISEASES
Sexually transmitted diseases (STD) are communicable diseases transmitted predominantly by sexual contact and caused by a wide range of bacterial, viral, protozoal, and fungal agents and ectoparasites. During the past two decades, STDs have undergone a dramatic transformation. First, the change in name from venereal diseases (V.D) to sexually transmitted diseases (STD) indicates this transformation.
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