Diseases

World Health Organisation (WHO) defines health as complete physical, mental, and social well-being. So, what are diseases? The disease represents any variation from the standard physical health of human beings. The classification of diseases is based on the affected body system, damaged organ, physiological alterations, pathological effects, causes or aetiology, progression, epidemiology, and prevalence. One disease may have characteristics belonging to each category. A major cause of the disease is infection by disease-causing microorganisms such as viruses, bacteria, fungi, and parasites. Parasites affecting humans may be protozoa or helminths. Some diseases affect one individual, while others can be spread from one person to another. 

What Are Diseases?

A disease is any unfavourable deviation from an organism’s normal functioning and structure. Various signs and symptoms signify the development of this abnormal state. A disease may be mild or severe depending on its aetiology.

The study of diseases is known as pathology. Medical practitioners first study the normal structural and functional conditions to understand diseases, referred to as homeostasis. Pathologists use this information to review a disease’s cause or aetiology and mechanisms of progression or pathogenesis. They also examine the structural changes that occur due to the disease known as morphological changes and the practical ramifications of these changes. Pathology facilitates an accurate diagnosis and correct treatment.

Homeostasis is the physiological balance of the body’s physical and chemical processes resulting in a condition of normal structure and function. Disease signifies a disruption in the homeostatic mechanisms. 

Classification of Diseases.

Topographic classification subdivides these conditions according to the body system or region affected, giving rise to neurological, cardiovascular, abdominal, and pelvic diseases. Furthermore, anatomical classification centres on the specific affected organ leading to heart, kidney, and pancreas diseases. 

Physiological classification concerns the functional disruption of body processes resulting in subgroups such as metabolic diseases like diabetes. On the other hand, pathological classification deals with the nature of the disease process. This category features neoplastic diseases like cancer.

Etiological classification is based on the causative agents culminating in four major groups. These include idiopathic, iatrogenic, communicable and non-communicable diseases.

Types of Diseases.

The four main types of diseases include:

• Infectious diseases or communicable diseases due to exposure to pathogens.
• Non-infectious diseases or non-communicable diseases are caused by various factors and pathogens but do not spread from one person to another.
• Degenerative diseases are caused by the deterioration of tissues and organs, like Alzheimer’s disease.
• Deficiency diseases are caused by insufficient nutrients and hormones, such as goitre and kwashiorkor. 

Causes of Diseases.

Students usually have two predominant questions. What are diseases, and what causes them? An abnormal physical state arises due to an unhealthy diet, stress, and external toxic agents. Lifestyle choices like excessive alcohol consumption, drug use, unprotected sex, and lack of exercise also shift the normal homeostasis. Furthermore, some microorganisms are responsible for diseases. These include viruses, fungi, parasites, and bacteria.

• Viral diseases.

Scientists do not consider viruses living organisms because they rely on the host cell for reproduction. These conditions include HIV, influenza, HPV, chickenpox, and herpes. The causes of viral diseases are the entry of a virus into the body, where it penetrates the cell. The virus spreads between cells and multiplies within them.

• Bacterial diseases.

Not all bacteria are pathogenic, as some exist as flora within the GIT to aid in digestion and immune function. Disease-causing bacteria include salmonella, staphylococcus, streptococcus, pseudomonas, and chlamydia. Bacteria enter the body through a cut and rapidly reproduce, resulting in a bodily reaction such as diarrhoea.

• Parasitic diseases.

Parasites depend on another organism, known as the host, for their survival. They may be protozoa or helminths. Examples of protozoan diseases include malaria and toxoplasmosis. Malaria is a common parasitic disease caused by Plasmodium and spread by the female anopheles mosquito. Furthermore, examples of helminth infections include schistosomiasis, ascariasis, and hookworm.

• Fungal diseases. 

Fungi such as yeast are non-pathogenic. Examples of fungal infections include athlete’s foot, fungal nail infection, histoplasmosis, candidiasis, and blastomycosis. 

Illness and Disease.

What are diseases, and how do they differ from illnesses? These terms are commonly used interchangeably without much consideration. Public health studies define and differentiate these terms.

Illness refers to the health problems an individual uses to describe their condition derived from their analysis of mental and physical symptoms. These symptoms may be mild, temporary, chronic, or severe and limit the person’s ability to lead a normal life.

Furthermore, the disease is a health condition discovered through a diagnosis from a certified medical practitioner. The diagnostic process involves using comprehensive, standardised laboratory and diagnostic strategies. The medical practitioner also determines the most likely causes and treatments. 

Conclusion.

Diseases encompass any divergence from the normal functioning and structure of the whole organism or a part such as an organ. The study of diseases is pathology. Understanding the different categories of diseases is essential in mastering pathology. The various diseases include non-communicable, communicable, deficiency, and degenerative diseases. Communicable and non-communicable diseases are clinically significant. Communicable diseases can spread from one person to another and are commonly caused by pathogens. Examples include HIV, TB, malaria, food poisoning, and flu. Moreover, non-communicable diseases are caused by external and internal agents and do not spread to others. These are cardiovascular diseases, diabetes, and Alzheimer’s disease.