diseases

Diseases are abnormal conditions that disrupt the structure or function of living organisms and cause distress, impairment, or death. They arise from a variety of causes, including infections by pathogens such as bacteria, viruses, fungi, and parasites; genetic or developmental defects; nutritional or metabolic problems; immune dysfunction; and environmental or lifestyle factors.

Diseases are commonly classified by etiology, mode of transmission, and duration. Infectious diseases are caused by pathogens and can spread between individuals or populations, while non-communicable diseases arise from non-infectious processes. Acute diseases present quickly and may resolve, whereas chronic diseases persist for extended periods, sometimes lifelong, and may have relapses.

Diagnosis involves medical history, physical examination, and specific laboratory tests or imaging studies to identify the cause and extent of impairment. Treatments vary accordingly and may include medications, surgery, rehabilitation, lifestyle changes, or palliative care. Prevention includes vaccination, sanitation, safe behavior, nutrition, and early screening to reduce incidence and improve outcomes.

Examples of diseases can be infectious, such as influenza and malaria, or non-infectious, such as diabetes, cardiovascular disease, cancer, and chronic respiratory conditions. Some conditions have multifactorial causes, involving genetic susceptibility combined with environmental triggers.

Public health efforts aim to monitor disease patterns, control outbreaks, and promote prevention. Access to timely diagnosis and effective treatment varies across populations, influencing prognosis and equity. Ongoing research seeks to understand mechanisms, develop new therapies, and improve prevention strategies.