Epidemiology of Communicable Diseases

Study Notes

Definition: Epidemiology is the study of the distribution and determinants of health-related events, diseases, or health-related characteristics among populations.
Key concepts:
- Incidence: number of new cases of a disease in a population over a specific period
- Prevalence: total number of existing cases of a disease in a population at a specific point in time
- Outbreak: sudden increase in the number of cases of a disease in a specific area
- Pandemic: outbreak that affects a large number of people across multiple countries
Epidemiological triangle:
- Agent: the pathogen or infectious agent
- Host: the person or animal that can be infected
- Environment: the external factors that contribute to the spread of the disease

Definition: Immunization is the process of inducing immunity to a specific disease through vaccination or exposure to a pathogen.
Types of immunity:
- Active immunity: occurs when the body produces its own antibodies in response to a pathogen
- Passive immunity: occurs when the body receives antibodies from an external source (e.g., vaccination, maternal antibodies)
Vaccination:
- Types of vaccines:
  - Inactivated vaccines (e.g., flu vaccine)
  - Live, attenuated vaccines (e.g., MMR vaccine)
  - Subunit vaccines (e.g., HPV vaccine)
- Vaccine schedules: recommended schedules for vaccination to ensure maximum protection against specific diseases

Modes of transmission:
- Direct transmission: direct contact between an infected person and a susceptible host (e.g., touching, kissing)
- Indirect transmission: transmission through a contaminated intermediate object or vector (e.g., food, water, insect vectors)
- Airborne transmission: transmission through the air (e.g., respiratory diseases like tuberculosis)
Factors that influence transmission:
- Infectivity: the ability of a pathogen to cause infection
- Susceptibility: the likelihood of a person becoming infected
- Virulence: the severity of the disease caused by a pathogen
- Environmental factors: climate, crowding, and sanitation can influence transmission

Epidemiology studies the distribution and determinants of health-related events, diseases, or health-related characteristics among populations.
Incidence measures the number of new cases of a disease in a population over a specific period.
Prevalence measures the total number of existing cases of a disease in a population at a specific point in time.
An outbreak is a sudden increase in the number of cases of a disease in a specific area.
A pandemic is an outbreak that affects a large number of people across multiple countries.

The agent is the pathogen or infectious agent responsible for the disease.
The host is the person or animal that can be infected.
The environment includes external factors that contribute to the spread of the disease.

Immunization is the process of inducing immunity to a specific disease through vaccination or exposure to a pathogen.
Active immunity occurs when the body produces its own antibodies in response to a pathogen.
Passive immunity occurs when the body receives antibodies from an external source (e.g., vaccination, maternal antibodies).

Inactivated vaccines contain killed or inactivated pathogens (e.g., flu vaccine).
Live, attenuated vaccines contain weakened pathogens (e.g., MMR vaccine).
Subunit vaccines contain only a small portion of the pathogen (e.g., HPV vaccine).
Vaccine schedules are recommended schedules for vaccination to ensure maximum protection against specific diseases.

Direct transmission occurs through direct contact between an infected person and a susceptible host (e.g., touching, kissing).
Indirect transmission occurs through a contaminated intermediate object or vector (e.g., food, water, insect vectors).
Airborne transmission occurs through the air (e.g., respiratory diseases like tuberculosis).
Infectivity refers to the ability of a pathogen to cause infection.
Susceptibility refers to the likelihood of a person becoming infected.
Virulence refers to the severity of the disease caused by a pathogen.
Environmental factors like climate, crowding, and sanitation can influence transmission.

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