Microbio Exam III: Public Health and Epidemiology

Pathology

study of disease

Etiology

cause of a disease

Pathology

study of disease

Etiology

cause of a disease

Pathogenesis

development of a disease

Infection

invasion/colonization of the body by pathogens

Disease

abnormal state in which the body is not performing normal functions

transient microbiota

may be present for days, weeks, or months

Normal microbiota

permanently colonize the host, do not cause disease under normal conditions

Human Microbiome Project

analyzes relationships between microbial communities on the body and human health

Distribution/composition of normal microbiota are determined by

nutrients, barriers, immune system

Microbial antagonism is also known as

competitive exclusion

How do normal microbiota protect their host?

compete for nutrients, produce substances harmful to invading microbes, affect pH and available oxygen

Symbiosis

relationship between normal microbiota and host

Types of symbiotic relationships

commensalism, mutualism, parasitism

Some normal microbiota are

opportunistic pathogens

Koch’s postulates: pathogen must be…

present in every case of the disease, isolated from the host and grown in pure culture, cause disease when inoculated in healthy animal, isolated from inoculated animal and shown to be original organism

Exceptions to Koch’s postulates

some pathogens cause several disease conditions/multiple diseases, some microbes have never been cultured

Incidence

number of people who develop a disease during a particular time period

Prevalence

number of people who develop a disease at a specified time, regardless of when it first appeared

Prevalence considers both

old and new cases

Sporadic disease

occurs only occasionally

Endemic disease

disease constantly present in a population

Epidemic disease

disease acquired by many people in an area in a short time

pandemic disease

worldwide epidemic

acute disease

rapid-onset symptoms, but short-lasting disease

chronic disease

symptoms develop slowly

subacute disease

intermediate between acute and chronic

latent disease

causative agent is inactive for a time, then activates and produces symptoms

herd immunity

immunity in most of a population

local infection

pathogens limited to specific area of the body

systemic (generalized) infection

infection throughout the body

focal infection

systemic infection that began as a local infection

sepsis

toxic inflammatory condition arising from spread of microbes, esp. bacteria/toxins, from focus of infection

septicemia

growth of bacteria in the blood; blood poisoning

primary infection

acute infection that causes initial illness

Secondary infection

opportunistic infection after primary/predisposing infection

presence of bacteria, virus, or toxins in blood

bacteremia, viremia, toxemia

Predisposing factors

make the body more susceptible to disease

examples of predisposing factors

sex, inherited traits, climate, vaccination status, fatigue, age, lifestyle, nutrition, chemotherapy

Incubation period

interval between initial infection and first symptoms

Prodromal period

short period after incubation - early mild symptoms

period of illness

disease is most severe

period of decline

symptoms decline

period of convalescence

body returns to its prediseased state

reservoirs

continual sources of infection

Types of reservoirs

human, animal, nonliving

Human reservoirs - carriers may have

inapparent infections, latent diseases

Zoonoses

diseases transmitted from animals to humans

Examples of nonliving reservoirs

soil, water

forms of contact transmission

direct, indirect, droplet

Direct contact transmission

requires close association between the infected and a susceptible host

Indirect contact transmission

spreads to a host by a nonliving object called a fomite

droplet transmission

transmission via airborne droplets less than 1m

types of vehicle transmission

water, food, air

vector transmission

arthropods, fleas, ticks, mosquitoes

general methods of vector transmission

mechanical, biological

mechanical transmission

arthropod carries pathogen on its feet

biological transmission

pathogen reproduces in the vector; transmitted via bites/feces

Healthcare-associated infections are also known as

nosocomial infections

Healthcare-associated infections affect

1 in 25 hospital patients

Healthcare-associated infections cause how many deaths annually

20K

Healthcare-associated infections are caused by

microbes in hospital environment, weakened host, chain of transmission in hospital

Compromised host

individual whose resistance to infection is impaired by disease, therapy, or burns

Universal precaution types

standard, transmission-based

standard precautions

basic, minimum practices

transmission-based practices

supplemental to standard precautions - designed for known or suspected infections

transmission-based precaution examples

contact, droplet, airborne

ways to reduce pathogens in a hospital setting

handwashing, disinfecting tubs, cleaning instruments scrupulously, using disposable bandages and intubation

Most emerging infectious diseases are

zoonotic, of viral origin, likely vector-borne

contributing factors to EIDs

genetic recombination, evolution of new strains, widespread use of antibiotics and pesticides, changes in weather patterns, modern transportation, expanding human settlements due to war, animal control measures, public health failure

EIDs caused by genetic recombination

E. coli and avian influenza

EIDs caused by evolution of new strains

vibrio cholerae

EIDs caused by changes in weather patterns

Hantavirus

EIDs caused by modern transportation

West Nile virus

EIDs caused by expanding human settlement

coccidioidomycosis

EIDs caused by animal control measures

Lyme disease

EIDs caused by public health failure

diphtheria

Epidemiology

study of where and when diseases occur and how they are transmitted in populations

First epidemiologists

John Snow (cholera), Semmelweis (handwashing advocate)

Epidemiologists determine

etiology of a disease

Epidemiologists identify

important factors concerning spread of disease

Epidemiologists develop

methods for controlling a disease

Epidemiologists assemble

data and graphs to outline incidence of disease

Descriptive epidemiology

collection and analysis of data (Snow)

Analytical epidemiology

analyzes a particular disease to determine probable cause (Nightingale)

Experimental epidemiology

involves hypothesis and controlled experiments (Semmelweis)

MMWR

Morbidity and Mortality Weekly Report, sent out by CDC

Morbidity

incidence of a specific notifiable disease

Mortality

deaths from notifiable diseases

Notifiable infectious diseases

diseases in which physicians are required to required to report occurrence

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

pathogenicity

ability to cause disease

virulence

degree of pathogenicity

portals of entry for pathogens

mucous membranes, skin, parenteral route

parenteral route

pathogen deposits directly into tissues when barriers are penetrated

ID 50 definition

infectious dose for 50% of a sample population

ID 50 measures

virulence of a microbe

LD 50 definition

lethal dose for 50% of a sample population

LD 50 measures

potency of a toxin

Almost all pathogens attach to host tissues in a process called

adherence