Introduction to Public Health and Diseases
Health and Disease
What is Health?
Health is a state of complete physical, mental, and social well-being. It is influenced by a series of factors such as:
- Heredity: Genetic factors
- Environment: Physical and chemical factors
- Personal Behavior: Lifestyle choices like diet and exercise
- Access to Health Systems: Availability of healthcare services
Health Risk and Risk Factors
Health risk is the probability of an event or damage to health that can cause illness or death. A risk factor is any circumstance or characteristic that increases the likelihood of a person developing a disease. There are two types of risk factors:
- Modifiable: These can be changed through behavior modifications, such as eating habits, alcohol consumption, and smoking.
- Non-modifiable: These cannot be changed, such as age, sex, and genetic predisposition.
Public Health and Preventive Medicine
Public health is the application of scientific methods to address health and disease problems. Preventive medicine focuses on preventing the onset and development of diseases in individuals, families, and populations. There are three levels of prevention:
- Primary Prevention: Aims to minimize the risk of diseases through measures like vaccination.
- Secondary Prevention: Focuses on early detection and intervention to prevent disease manifestations.
- Tertiary Prevention: Aims to slow disease progression and prevent complications.
Preventive measures can be targeted at different levels:
- Universal Measures: Target the entire population.
- Selective Measures: Target specific groups within the population.
- Individual Measures: Target a particular individual.
Types of Diseases
A disease is a disorder that causes physical and mental disturbances in normal body functions. Pathology refers to the changes that occur in the body due to the disease. Diseases can be classified into several categories:
Infectious Diseases
Infectious diseases are caused by pathogenic microorganisms such as bacteria, viruses, fungi, and parasites. Examples include:
- Bacterial infections
- Viral infections
- Fungal infections
- Parasitic infections
Non-infectious Diseases
Non-infectious diseases are not caused by pathogens. Examples include:
- Hereditary Diseases: Inherited from parents, some are chronic and lifelong (e.g., diabetes).
- Mental Illnesses: Characterized by imbalances in personality (e.g., psychosis, schizophrenia).
- Organ-Specific Diseases: Affecting specific organs (e.g., chronic bronchitis).
- Autoimmune Diseases: Caused by a malfunctioning immune system.
- Diseases Caused by Accidents: Such as traffic accidents.
Classification of Diseases based on Occurrence
- Sporadic Diseases: Occur in isolated cases within a population (e.g., stroke).
- Endemic Diseases: Occur consistently in specific geographical areas (e.g., leprosy, malaria).
- Epidemic Diseases: Affect a large number of people within a short period (e.g., HIV, influenza A). If an epidemic spreads across multiple countries, it is called a pandemic.
Infectious Diseases
Prevalence and Incidence
Prevalence refers to the number of people with a specific disease at a particular time. Incidence refers to the number of new cases of a disease within a specific period.
Characteristics of Pathogens
- Infectivity: The ability of a pathogen to spread.
- Infectiousness: The ability of a pathogen to establish itself and multiply in a host.
- Pathogenicity: The ability of a pathogen to cause disease.
- Virulence: The degree of pathogenicity.
Routes of Infection
- Fecal-Oral Route: Ingestion of contaminated food or water.
- Respiratory Route: Inhalation of airborne droplets containing pathogens.
- Direct Contact: Contact with infected individuals or animals.
Reservoir of Infection
A reservoir of infection is a person, animal, or environment that harbors a pathogen and can transmit it to others.
Phases of Infectious Diseases
- Incubation Period: The time between pathogen entry and the appearance of the first symptoms.
- Prodromal Period: Characterized by non-specific general symptoms.
- Clinical Period: The stage where specific symptoms and signs of the disease manifest.
Immunity and Defense Mechanisms
The Immune System
The immune system defends the body against pathogens and foreign substances. Immunity is the resistance to infections. The immune response is the body’s reaction to pathogens.
Types of Immunity
- Innate Immunity: Present from birth, provides non-specific defense mechanisms (e.g., white blood cells, inflammation).
- Adaptive Immunity: Acquired throughout life, provides specific defense mechanisms (e.g., lymphocytes, antibodies).
External Defenses
The body’s first line of defense against pathogens includes:
- Skin
- Mucous membranes
- Saliva
- Tears
- Urine
- Biological barriers
Treatment of Infectious Diseases
- Sera: Contain pathogen-specific antibodies.
- Vaccines: Contain weakened or inactive pathogens to stimulate immunity.
- Drugs: Such as antibiotics to kill or inhibit the growth of pathogens.