chapter 16

Define epidemiology

The study of how diseases are distributed in populations and the factors that influence or determine this distribution. It involves identifying the causes

Why should we study epidemiology?

• To understand how diseases spread 

• To identify risk factors 

• To develop prevention strategies 

• To control outbreaks and pandemics 

• To protect public health and improve outcomes 

Host – the human or animal that harbors the disease

Environment – conditions that allow the disease to be transmitted (e.g.

temperature

Define etiology

The study of the cause of a disease

Define incidence

The number of new cases in a given time

Define prevalence

The total number of cases (new and existing) at a given time

What is morbidity rate?

The proportion of illness in a population

What is mortality rate?

The proportion of deaths in a population

What does endemic mean?

A disease that is constantly present in a population (e.g.

What is an epidemic?

A sudden increase in disease cases in a specific area

What is a pandemic?

An epidemic that spreads worldwide (e.g.

What does sporadic mean?

A disease that occurs occasionally and randomly

What is a common source outbreak?

An outbreak where all cases come from a single source (e.g.

cases spike quickly and then decline

What is a propagated epidemic?

A disease that spreads person-to-person

cases rise slowly and show multiple peaks as it continues through the population (e.g.

influenza)

What are portals of entry for pathogens?

Skin

What are portals of exit for pathogens?

Respiratory droplets

What is direct contact transmission?

Person-to-person transmission (e.g.

What is indirect contact transmission?

Transmission via fomites (nonliving objects like doorknobs

What is droplet transmission?

Transmission via sneezing or coughing (travels short distances)

What is waterborne transmission?

Transmission through contaminated water (e.g.

What is airborne transmission?

Transmission through dust or droplets that travel long distances

What is foodborne transmission?

Transmission through contaminated or undercooked food

What is a mechanical vector?

An insect that passively carries pathogens (e.g.

What is a biological vector?

An insect in which the pathogen lives and multiplies (e.g.

What is a nosocomial infection?

A hospital-acquired infection that occurs during a hospital stay

What is an exogenous nosocomial infection?

An infection that comes from outside the body

What is an endogenous nosocomial infection?

An infection caused by the patient’s own microbiota when it enters sterile areas (e.g.

What is the most common nosocomial infection and its causative agent?

Urinary tract infections (UTIs)

How can nosocomial infections be prevented?

Hand hygiene