Chapter 14: Disease and Epidemiology

pathology

study of disease

etiology

cause of disease

pathogenesis

manner in which the disease develops or progresses

infection

invasion or colonization or the body by pathogenic microorganisms

disease

occurs when an infection results in a change from a state of health; all or part of the body is not able to perform its normal function

normal microbiota

microorganisms that establish permanent residence in our bodies and do not cause disease under normal conditions

microbial antagonism/competitive exclusion

once the normal microbiota are established they can prevent the overgrowth of harmful microorganisms

symbiosis

relationship between two organisms in which at least one organism is dependent on the other

commensalism

one organism benefits and the other is unaffected

mutualism

both organisms benefit

parasitism

one benefits and the other (host) is harmed

opportunistic pathogens

microorganisms that normally do not cause disease in a normal healthy person in their normal habitat but may do so in a different environment

symptoms of infectious disease

changes in body functions, pain, malaise; subjective and may not be observable to others

signs of infectious disease

objective changes, lesions, swelling, fever, paralysis

syndrome

a specific set of symptoms or signs that always accompany a particular disease

communicable disease

a disease that spreads from one host to another, either directly or indirectly, chicken pox, measles, genital herpes, etc.

contagious disease

ones that are spread very easily

noncommunicable disease

not spread from one host to another-these diseases are caused by microorganisms that normally live in the body and only occasionally produce disease or by microorganisms that normally live outside the body and only produce disease when introduced to the body

incidence

number of people in a population who develop a disease during a particular time period-indicates spread of disease

prevelance

number of people in a population who develop a disease at a specific time regardless of when it first appeared

sporadic disease

a disease that occurs only occasionally

endemic disease

a disease that is constantly present in a population

epidemic disease

if a large number of people in a given area acquire a specific disease in a short period of time

pandemic disease

an epidemic disease that occurs world wide

acute disease

disease that develops rapidly and last only a short time

chronic disease

develops more slowly and the body's reactions may be less severe but the disease is likely to continue or reoccur for long periods

subacute disease

intermediate acute and chronic

latent disease

one in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease

local infection

the invading microorganisms are limited to a small area of the body

systemic infection

microorganisms or their products are spread throughout the body by the blood or lymph

sepsis

toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins from an area of infection

septicemia

systemic infection arising from the multiplication of pathogens in the blood

bacteremia

presence of bacteria in the blood

toxemia

presence of toxins in the blood

viremia

presence of viruses in the blood

primary infection

acute infection that causes the initial illness

secondary infection

one caused by opportunistic pathogen after the primary infection has weakened the immune system

subclinical infection

an infection that does not cause any noticeable illness

predisposing factors

things that make the body more susceptible to a disease and may alter the course of the disease

contact transmission

spread of an agent of disease by direct contact (touching), indirect contact (doorknob, tables, other objects) or droplet transmission (sneezing, coughing micro droplets, and someone else inhaling)

direct contact transmission

the direct transmission of an agent by physical contact between a source and the susceptible host

indirect contact transmission

occurs when the agent of disease is transmitted from its reservoir (the infected person) to a susceptible host by means of nonliving objects

fomite

the general term for any nonliving object involved in the spread of an infection

droplet transmission

microbes are spread in droplet nuclei = mucus droplets

vehicle transmission

transmission of disease by agents by a medium such as water, food or air, blood or other body fluids

waterborne transmission

type of vehicle transmission; usually pathogens are spread by water contaminated with untreated or poorly treated sewage

foodborne transmission

pathogens are generally transmitted in foods that are incompletely cooked, poorly refrigerated, or prepared under unsanitary conditions

airborne transmission

spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from the reservoir to the host

vectors

animals that carry pathogens from one host to another

mechanical transmission

the passive transport of the pathogens on the insect's feet or other body parts

biological transmission

active process; the insect or animal bites an infected person or animal and ingests some of hte infected blood; pathogens then produce in the vectors

nasocomial infections

infections do not show any evidence of being present or incubating at the time of admission to a hospital; acquired as a result of a hospital stay

microorganisms in the hospital environment

generally, because of the high level of antibiotic use in hospitals there is a selection for antibiotic resistant strains and typically hospital acquired infections will be with bacteria that are resistant to antibiotic to some degree

c. difficile

part of our normal microbiota of the gut but can cause serious bouts of diarrhea that can lead to ruptured intestines if it overgrows and produces virulence factors

staphylococci

multi-drug resistant

e. coli

especially important in UTIs catheters increase risk

enterococci

gram (+) cocci that is typically found in the colon, has emerged as an important cause of blood infections; increase in prevalence of antibiotic resistant strains; group D strep; were classified until RNA reclassified them; found in intestines; almost over 80% are multidrug resistant

ancietobacter naumannii

wounded soldiers picked this up from soil; most strains are multidrug resistant

compromised host

broken skin/mucus membranes and suppressed immune system

chain of transmission

direct contact transmission and indirect contact transmission

control

handwashing and universal precautions

universal precautions

guidelines from the center for disease control and prevention

transmission based precautions

enhanced precautions in individuals with suspected infections that are known to spread easily

epidemiology

the science that studies when and wehre diseases occur and how they are transmitted in populations

emerging infectious diseases

diseases that are new, increasing in incidence, or showing a potential to increase in the near future

monkey pox

an orthopoxvirus related to small pox but much less deadly; seems to spread mainly via close contact with infected individuals; pustules can form in any epithelia, can cause major scarring and blindness; high fever and flu-like symptoms

SARS CoV 1

more pathogenic than current SARS CoV 2; 10% mortality

SARS CoV 2

not as pathogenic or deadly as SARS CoV 1 but much easier to spread; spread with asymptomatic carriers

ebola virus

first appeared in 70s; hemorrhagic virus; major outbreak in 2014

zika

virus transmitted by mosquitos that can cause birth defects (microcephaly)

center for disease control/prevention (CDC)

branch of the US public health service it is our source for epidemiological info in the US publishes a weekly morbidity and mortality report

morbidity

the incidence of specific notifiable disease

mortality

the number of deaths from these diseases

morbidity rate

number of people affected in relation to the total population in a given time period

mortality rate

number of deaths from a disease in relation to the population in a given time

incubation period

during this time there is no signs or symptoms of infection; the time involved depends on the microorganism, the number of infecting organisms, adn the resistance of the host

prodromal period

early mild symptoms

period of illness

the disease is most severe; person exhibits signs and symptoms like fever, chills, weakness, etc.

period of decline

the signs and symptoms subside