Chapter 16 study guide Flashcards
The field of _____ concerns the geographical distribution and timing of infectious disease occurrences and
how they are transmitted and maintained in nature, with the goal of recognizing and controlling outbreaks.
epidemiology
The state of being diseased is called
morbidity
The_______ can be expressed as the number of diseased individuals out of a standard number of individuals
in the population, such as 100,000, or as a percent of the population.
morbidity rate
A _____rate can be expressed as the percentage of the population that has died from a disease or as the number of deaths
per 100,000 persons (or other suitable standard number).
mortality
is the number, or proportion, of individuals with a particular illness in a given population at a point in
time.
prevalence
is the number or proportion of new cases in a period of time.
incidence
diseases that are seen only occasionally, and usually without geographic concentration, are called ?
ex. tetanus, rabies, and plague
sporadic diseases
Diseases that are constantly present (often at a low level) in a population within a particular geographic region are
called
ex. malaria
endemic disease
Diseases for which a larger than expected number of cases occurs in a short time within a geographic region are
called
ex. influenza
epidemic
An ______ that occurs on a worldwide scale is called a pandemic disease
ex. HIV/AIDS and novel influenzas virus
pandemic
The main national public health agency in the United States is __________, an agency of the Department of Health and Human Services.
CDC
was a British physician known as the father of epidemiology for determining the source of
the 1854 Broad Street cholera epidemic in London.
Jon Snow
In an _______, data are gathered from study participants through measurements (such as physiological
variables like white blood cell count), or answers to questions in interviews (such as recent travel or exercise
frequency).
observational study
_________ gather data from the past on present-day cases. Data can include things like the medical
history, age, gender, or occupational history of the affected individuals.
retrospective studies
are typically retrospective and compare a group of individuals with a disease to a similar
group of individuals without the disease.
case control studies
follow individuals and monitor their disease state during the course of the study. Data on the
characteristics of the study subjects and their environments are gathered at the beginning and during the study so
that subjects who become ill may be compared with those who do not.
prospective studies
involve manipulation of subjects, they are typically more difficult and sometimes impossible
for ethical reasons.
experimental studies
can be living organisms or nonliving sites. Nonliving reservoirs can include soil and water in the environment. These
may naturally harbor the organism because it may grow in that environment. These environments may also become
contaminated with pathogens in human feces, pathogens shed by intermediate hosts, or pathogens contained in the
remains of intermediate hosts.
reservoirs
For pathogens to persist over long periods of time they require ____ where they normally reside.
reservoirs
A ____ is contaminated with the pathogen and can mechanically transmit it to another host; however, a passive
carrier is not infected.
passive carrier
For example, a health-care professional who fails to wash his hands after seeing a patient
harboring an infectious agent could become a passive carrier, transmitting the pathogen to another patient who
becomes infected.
passive carrier
is an infected individual who can transmit the disease to others
active carrier
For example, _______ may transmit the disease during the
incubation period (before they show signs and symptoms) or the period of convalescence (after symptoms have
subsided).
active carriers
Active carriers who do not present signs or symptoms of disease despite infection are called
asymptomatic carriers
Pathogens such as hepatitis B virus, herpes simplex virus, and HIV are frequently
transmitted by
asymptomatic carriers
In parasitic infections, the parasite’s preferred host is called the
definitive host
In parasites with complex life
cycles, the ______ is the host in which the parasite reaches sexual maturity.
definitive host
includes direct contact or indirect contact
contact transmission
Here the agent is transmitted by physical contact between two individuals
through actions such as touching, kissing, sexual intercourse, or droplet sprays.
can be categorized as
vertical, horizontal, or droplet transmission.
direct transmission
Often, contact between mucous membranes is required for entry
of the pathogen into the new host, although skin-to-skin contact can lead to mucous membrane contact if the new
host subsequently touches a mucous membrane.
horizontal direct contact transmission
occurs when pathogens are
transmitted to a fetus or infant during pregnancy, birth, or breastfeeding.
vertical direct contact transmission
When an individual coughs or sneezes, small droplets of mucus that may contain pathogens are ejected. This leads
to direct
droplet transmission
involves inanimate objects called fomites that become contaminated by pathogens
from an infected individual or reservoir
indirect contact transmission
For example, an individual with the common cold may
sneeze, causing droplets to land on a fomite such as a tablecloth or carpet, or the individual may wipe her nose and
then transfer mucus to a fomite such as a doorknob or towel.
indirect contact transmission
The term _____ refers to the transmission of pathogens through vehicles such as water, food, and
air.
vehicle transmission
Although droplet transmission over short distances is considered ______ as discussed above,
longer distance transmission of droplets through the air is considered
contact transmission
vehicle transmission
Tuberculosis is often transmitted via airborne transmission when the causative agent, Mycobacterium tuberculosis,
is released in small particles with
coughs
Because tuberculosis requires as few as ______to initiate a new
infection, patients with tuberculosis must be treated in rooms equipped with special ventilation, and anyone
entering the room should wear a mask.
10 microbes
an animal
that carries a pathogen from one host to another without being infected itself. For example, a fly may land on fecal
matter and later transmit bacteria from the feces to food that it lands on; a human eating the food may then become
infected by the bacteria, resulting in a case of diarrhea or dysentery
mechanical vector
that transmits the
pathogen from one host to another (Figure 16.12). Arthropods are the main vectors responsible for biological
transmission (Figure 16.13). Most arthropod vectors transmit the pathogen by biting the host, creating a wound that
serves as a portal of entry. The pathogen may go through part of its reproductive cycle in the gut or salivary glands of
the arthropod to facilitate its transmission through the bite.
biological vectors
carries a pathogen on its body from one host to another, not as an infection
mechanical vector
carries a pathogen from one host to another after becoming infected itself.
biological vector
Infections acquired in health-care facilities, including hospitals, are called
nosocomial infections or healthcare
associated infections (HAI)
In 2011, more than 720,000 ____occurred in hospitals in the United States, according to the CDC.
HAI
