Disease



A disease is an illness, sickness, or abnormal condition of an organism that impairs bodily functions and is often characterized by typical symptoms (problems) and signs (physical findings). Diseases or unhealthy states can be caused by infection, diet or other conditions of life, or may be inherited.

Epidemiology is the branch of medical science which investigates and describes the causes and spread of disease and develops the means for prevention or control. Epidemiologists may study many different illnesses, often focusing on major infectious diseases such as influenza or chickenpox. Epidemiologists can be separated into two groups—research and clinical.

Chronic disease
Chronic (long-term) diseases—such as heart disease, cancer, and diabetes—are the leading causes of death and disability in the United States. Chronic diseases account for 70% of all deaths in the U.S., which is 1.7 million each year. These diseases also cause major limitations in daily living for almost 1 out of 10 Americans or about 25 million people. Although chronic diseases are among the most common and costly health problems, they are also among the most preventable. Adopting healthy behaviors such as eating nutritious foods, being physically active, and avoiding tobacco use can prevent or control the devastating effects of these diseases.

Infectious disease

 * Main Article: Infectious disease

Infectious diseases (also called communicable diseases) are diseases caused by germs. Germs are microbes (microscopic organisms) that are found everywhere - in air, soil and water. You can get infected by touching, eating, drinking or breathing something that contains a germ. Germs can also spread through animal and insect bites, kissing, sexual contact, blood transfusions, or by entering wounds. Vaccines, proper hand washing and medicines can help prevent infections.

Infectious diseases kill more people worldwide than any other single cause.

Symptoms
A symptom is any sensation or change in bodily function that is experienced by a patient who is suffering from a particular disease. Symptoms are frequently seen as simply a departure from normal function or feeling which is noticed by a patient. They indicate the presence of an abnormality, and are therefore used by physicians to diagnose specific ailments. For example, symptoms of the common flu (influenza virus) include the following:
 * Fever (usually high)
 * Headache
 * Tiredness (can be extreme)
 * Cough
 * Sore throat
 * Runny or stuffy nose
 * Body aches
 * Diarrhea and vomiting (more common among children than adults)