Infection and Infectious Diseases Notes

Infection, Infectious Diseases and Epidemiology Notes

Terms

  • Normal Flora / Normal Microbiota

    • Refers to the microorganisms that routinely inhabit the body without causing disease.

  • Pathogen

    • A microorganism that can cause disease.

  • Microbial Antagonism

    • The competition between the normal microbiota and pathogens for nutrients and space.

  • Opportunists

    • Organisms that can cause disease when the host's defenses are compromised.

Disease Occurrence

  • Incidence

    • The number of new cases in a given time period, e.g. 1,200,000 cases.

  • Prevalence

    • The total number of cases at a particular point in time, e.g. 1,000,000 cases.

  • Types of Occurrence:

    • Sporadic: Occasional cases at irregular intervals.

    • Endemic: Constant presence of a disease in a specific geographic area.

    • Epidemic: An increase in cases above the normal level in a population.

    • Pandemic: An epidemic that spreads across multiple countries or continents.

Reporting of Infectious Diseases

  • Health Department Reporting:

    • Physicians, labs, and hospitals are mandated to report certain diseases.

  • CDC Morbidity and Mortality Weekly Report (MMWR):

    • Weekly updates on the occurrences of notifiable diseases.

Types of Infections

  • Local Infection: Infection limited to a specific area.

  • Systemic Infection: Infection that spreads throughout the body.

  • Bacteremia: Bacteria in the blood.

  • Septicemia: Systemic infection resulting from the presence of pathogenic organisms in the blood.

  • Primary Infection: The first infection that occurs in a patient.

  • Secondary Infection: An infection that occurs following a primary infection.

Reservoirs and Spread of Infection

  • Reservoirs:

    • Humans: A common source of pathogens.

    • Animals (Zoonoses): Diseases that can be transmitted from animals to humans.

    • Fomites: Inanimate objects that can carry infectious organisms.

Transmission of Infection

  • Modes of Transmission:

    • Contact:

    • Direct: Direct physical interaction.

    • Indirect: Through a fomite.

    • Droplet: Respiratory droplets from coughs or sneezes.

    • Vehicle Transmission:

    • *Water, Food, Air, Blood. *

    • Vectors:

    • Mechanical: Pathogen carried on the surface of a vector.

    • Biological: Pathogen develops inside the vector.

Healthcare-Associated (Nosocomial) Infections

  • Definition: Infections acquired in a healthcare setting.

    • Factors influencing nosocomial infections:

    • Presence of microorganisms in the hospital environment.

    • Transmission through healthcare staff and immunocompromised patients.