Understanding Health and Disease: Key Concepts and Types
Health and Disease: The WHO defines health as the state of complete physical, mental, and social well-being, not merely the absence of disease or ailments. A healthy person should feel good in their body, have harmony in their emotional life and mind, and integrate into society and the environment in which they are immersed.
Term Illness: Illness is the alteration of an individual’s health, i.e., the loss of balance between physical, mental, and social aspects.
Types of Disease
The causes of disease may be external (pathogens and environmental conditions) or internal (individual susceptibility). External factors include:
- Infectious: Caused by biological pathogens, physical, or chemical agents entering the body through direct or indirect infection (e.g., influenza).
- Social: Affect individuals and society as a whole, both in causes and consequences (e.g., drug dependence).
- Professional: Resulting from the development of certain work activities (e.g., hearing loss).
- Traumatic: Changes in health resulting from accidents that cause injuries, fractures, etc.
Internal factors include:
- Congenital and Hereditary: Congenital abnormalities often occur during pregnancy or childbirth (e.g., hydrocephalus), while hereditary diseases are transmitted through genes.
- Functional: Produced by alterations in the functioning of any organ (e.g., heart).
- Mental Disorders: Originating in the nervous system, these produce changes in behavior with temporary or permanent loss of capacity to adapt (e.g., schizophrenia).
- Nutritional: Alterations caused by poor diet, such as rickets, obesity, or anorexia.
Concepts of Epidemiology
Epidemiology is the science that studies how diseases affect groups of people in a specific place and time. When a disease appears suddenly in a particular region and affects a high number of people, it is referred to as an epidemic (e.g., measles in Spain). Diseases that persist for years are called endemic (e.g., malaria in the tropics), while those that spread across countries are termed pandemics (e.g., AIDS).
Disease Transmission
A pathogen is any factor that can cause damage to the body, disrupting the balance that maintains health. Pathogenic agents are classified as biological, chemical, physical, and social agents. Pathogens can be transmitted to a healthy person from the environment or another living being, producing disease through:
- Direct Transmission: Occurs without intermediaries, such as contact with sick animals, coughing, or sneezing.
- Indirect Transmission: Takes place through a living intermediary (vector) or via contaminated objects.
Types of Pathogenic Agents
Biological pathogens, also called germs, are living beings capable of causing disease. The main types include:
- Viruses: Obligate intracellular parasites that distort cellular functioning (e.g., AIDS, influenza).
- Bacteria: Single-celled organisms (e.g., cholera).
- Protozoa: Unicellular organisms responsible for diseases like malaria.
- Fungi: Produce various types of mycosis (e.g., athlete’s foot).
- Metazoans: Multicellular beings with a great diversity of forms (e.g., mites).
Chemical Pathogenic Agents: Can cause food poisoning by acting as toxic compounds found in spoiled food or introduced through bites or stings from animals.
Other Pathogenic Agents
There are four types of harmful agents:
- Radiation (e.g., X-rays)
- Loud noise above 75 decibels
- Blunt objects causing injury
- Psychic, social, and cultural changes (e.g., accelerated pace of life, war, economic problems, social discrimination)
Infectious Diseases
Infectious diseases are characterized by their ease of transmission and ability to infect the body. A sick person can transmit the disease to another healthy individual (e.g., through sneezing). These diseases typically have three periods: incubation, development, and convalescence. They are studied through a cycle of infection that distinguishes:
- The etiologic agent causing the disease
- The reservoirs of the pathogen
- The exit of the germ
- The mode of transmission (direct or indirect)
- The gateway into the body of the recipient
- The susceptibility to the disease
The Pandemic
Pandemics are diseases that spread over a wide geographic area and often result in numerous deaths. They typically occur when a new pathogen emerges to which people have little immunity and spreads easily. Countries may delay the arrival of the disease by closing borders. Current pandemics include AIDS, SARS, malaria, and tuberculosis. Other diseases that could become pandemics in the future include dengue fever and Buruli ulcer.
In wartime, an epidemic can reach pandemic proportions, as seen with typhus.