Disease
An impairment of the normal state of the living animal or plant body or one of its parts
that interrupts or modifies the performance of the vital functions, is typically manifested
by distinguishing signs and symptoms, and is a response to environmental factors (as
malnutrition, industrial hazards, or climate), to specific infective agents (as worms,
bacteria, or viruses), to inherent defects of the organism (as genetic anomalies), or to
combinations of these factors (1)
Diseases may be characterized as infectious / communicable / non-communicable,
acute / chronic, mild / severe,
Infectious disease
Infectious diseases are caused by pathogenic microorganisms, such as bacteria,
viruses, parasites or fungi;. (2) Some — but not all — infectious diseases spread
directly from one person to another. Infectious diseases that spread from person to
person are said to be contagious/communicable (5)
Contagious/communicable disease
Contagious/communicable diseases are infectious diseases communicable by contact
with one who has it, with a bodily discharge of such a patient, or with an object touched
by such a patient or by bodily discharges (3,4)
Noncommunicable diseases
Noncommunicable diseases (NCDs), are not passed from person to person. (6)
Acute and ChronicDisease
Acute conditions are severe and sudden in onset. This could describe anything from a
broken bone to an asthma attack. A chronic condition, by contrast is a long-developing
syndrome, such as osteoporosis or asthma. Note that osteoporosis, a chronic
condition, may cause a broken bone, an acute condition. An acute asthma attack
occurs in the midst of the chronic disease of asthma. Acute conditions, such as a first
asthma attack, may lead to a chronic syndrome if untreated. (1)
Mild and Severe diseases
Diseases are also characterized as mild/severe, with definitions depending on the
clinical manifestations of the respective disease.
(1) Merriam-Webster Dictionary: disease
(2) WHO: Infectious diseases
(3) Merriam-Webster Dictionary: contagious disease
(4) Merriam-Webster Dictionary: communicable disease
(5) kidshealth.org:infectious disease
(6) WHO: Non-communicable disease
(7) NIH Medline Plus: Acute vs. Chronic Conditions