MB Ch14 Disease and Epidemiology

spread of disease

factors that contribute to the _____ __ _____ in the modern world:

• overpopulation

• modern travel

• mass production and distribution of food and goods

epidemiology

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

pathology

study of disease

pathogen

disease-causing microbe

etiology

study of the cause of a disease

pathogenesis

development of disease

infection

colonization of the body by pathogens

disease

abnormal state in which the body is not functioning normally (change in a state of health)

morbidity

incidence of a specific disease (condition of being diseased)

notifiable infectious disease

disease that physicians must report to US Public Health Dept

• allows authorities to monitor disease

• provides early warnings of outbreaks

World Health Organization

organization that provides global surveillance of diseases

virulence

degree of pathogenicity of a microbe (how harmful a microbe is)

normal microbiota

microbes that colonize a human but do not produce disease under normal conditions/habitat

transient microbiota

microbes that may be present in a human for several days to months, then may disappear

distribution of normal microbiota

factors that determine the _____ __ _____ _____:

• O2, CO2

• salinity

• light/darkness

• moisture/dryness

• nutrient availability

• pH

microbial antagonism

when normal microbiota benefit the host by preventing the overgrowth of harmful microbes; aka competitive exclusion

• battle for nutrients

• production of harmful substances

• changing local pH

symbiosis

2 different organisms/populations living together

• relationship exists between humans and normal microbiota

• types: commensalism, mutualism, parasitism

commensalism

symbiotic relationship where one organism benefits and the other is unaffected

• ex. human and corynebacteria (live on eye)

  • human receives and loses nothing

  • corynebacteria receives habitat, O2 and nutrients from tears

mutualism

symbiotic relationship where both organisms benefit

• ex. human and E. coli in large intestine

  • human receives microbial antagonism, vitamin K

  • E. coli receives habitat

probiotics

live microbial cultures applied to or ingested to exert a beneficial effect; growth is selectively promoted by prebiotics

parasitism

symbiotic relationship where one organism benefits while the other is harmed; nutrients are extracted from host

• ex. human and Giardia

  • human loses nutrients from large intestine, gets diarrhea

  • Giardia receive habitat, nutrients from large intestine

opportunistic pathogens

do not cause disease in normal habitat of healthy person, but may do so in a different environment

• ex. E. coli is harmless in large intestine, but can cause disease/infection in urinary bladder, lungs, spinal cord, wounds

Koch’s postulates

showed that microbes caused disease, used to determine etiology

• showed that anthrax is caused by B. anthracis

association; isolation; inoculation; re-isolation

Koch’s postulates:

1. _____: the same pathogen must be present in every case of the disease

2. _____: pathogen must be isolated from the diseases host and grown in pure culture

3. _____: pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible lab animal

4. _____: pathogen must be isolated from the inoculated animal and must be shown to be the original pathogen

answer format: []; []; []; []

symptom

change in body function that is felt by a patient as a result of the disease

• not apparent to observer

• pain, malaise

sign

change in a body that can be measured or observed as a result of disease

• lesions, swelling, fever, paralysis

syndrome

specific group of signs and symptoms that accompany a disease

communicable disease

disease that is spread from one host to another

• ex. chickenpox, measles, genital herpes, tuberculosis

contagious disease

disease that is easily spread from one host to another

• ex. chickenpox, measles

noncommunicable disease

disease that is NOT transmitted from one host to another; caused by microbes that reside outside body or from normal microbiota that occasionally cause disease

• ex. Clostridium tetani

incidence

fraction of a population that contracts a disease during a specific time

• indicator of spread

• studying AIDs in mid-1990s

prevalence

fraction of a population having a specific disease at a given time regardless of when it appeared

sporadic disease

disease that occurs occasionally in a population

• ex. typhoid fever

endemic disease

disease constantly present in a population

• ex. common cold, COVID

epidemic disease

disease acquired by many hosts in a given area in a short time

• ex. influenza, STDs

pandemic disease

worldwide epidemic

• ex. AIDs, occasionally influenza

immunity

The rate at which disease spreads depends on the population’s _____.

herd immunity

immunity in most of a population

acute disease

symptoms develop rapidly; only lasts a short time

• influenza

chronic disease

disease develops slowly; likely to continue or recur for long periods

• ex. mononucleosis, Hep B, tuberculosis

subacute disease

disease symptoms are between acute and chronic

• ex. sclerosing panencephalitis (rare brain disease)

latent disease

disease with a period of no symptoms when the causative agent is inactive

• ex. shingles

predisposing factors

make the body more susceptible to disease; may alter the course of the disease

• short urethra in females (more UTIs)

• inherited traits, such as sickle cell gene

• climate and weather

• fatigue

• environment

• nutrition

• age

• occupation

• preexisting illness

• lifestyle

• chemotherapy

incubation period; prodromal period; period of illness; period of decline; period of convalescence

stages of disease:

1. _____ _____: interval between initial infection and first appearance of signs/symptoms

2. _____ _____: early, mild symptoms of disease (aches, malaise); short period

3. _____ __ _____: disease is most severe; overt signs and symptoms; if not overcome, patient dies

4. _____ __ _____: signs and symptoms subdue

5. _____ __ _____: person regains strength and body returns to pre-diseased state; recovery has occurred, but can still spread infection

answer format: []; []; []; []; []

reservoir of infection

continual source of infection; may be humans, animals, or non-living

humans

reservoir of infection: carrier; may have no sign of illness

• spread HIV, gonorrhea, hepatitis, amoebic dysentery

animals

reservoir of infection: zoonoses; can transmit to humans

• spread rabies, Lyme disease

non-living

reservoir of infection: soil, water, improperly stored/prepared food

• spread botulism, tetanus, ringworm

contact transmission

spread of pathogens through contact

• types: direct, indirect, droplet

direct

contact transmission: person-to-person transmission by physical contact

• ex. touching, kissing, sexual intercourse

• spreads influenza, staph infections, STDs, mono

indirect

contact transmission: use of a non-living object

• fomite: non-living material used in transmission

• ex. tissues, towels, bedding, cups, money, eating utensils

droplet

contact transmission: microbes spread in droplet nuclei (mucus droplets); travel only short distances

• ex. coughing, sneezing, laughing, talking

• spreads influenza, pneumonia, pertussis (whooping cough)

vehicle transmission

spread of pathogens using a medium

• types: waterborne, foodborne, airborne

waterborne

vehicle transmission: water contaminated with untreated or poorly treated sewage

• spreads cholera, shigellosis

foodborne

vehicle transmission: incompletely cooked, poorly refrigerated, prepared under unsanitary conditions

• spreads food poisoning, tapeworm infestation

airborne

vehicle transmission: droplet nuclei in dust that travel more than 1 meter from reservoir to host

• spreads tuberculosis, measles

vector transmission

spread of pathogens from one host to another using an animal carrier (typically arthropods)

• types: mechanical, biological

mechanical

vector transmission: passive transport on insect’s feet or other body part

biological

vector transmission: needs vector to perform active process, such as insect bites

nosocomial infections

hospital-acquired infections that affect 5-15% of all hospital patients

compromised host

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

• broken skin or mucous membranes

• suppressed immune system

chain of transmission

2 principle routes of transmission:

• direct: staff to patient, patient to patient

• indirect: fomites, hospital ventilation system

emerging infectious disease (EID)

new or changing disease that is increasing or has the potential to increase in incidence; criteria:

• symptoms are clearly distinct from other diseases

• identification of a new pathogen

• local disease becomes widespread

• rare disease becomes common

• mild disease becomes more severe

Snow

person: determined cholera originated from contaminated pump water in London

Semmelweis

person: showed that washing hands reduced mortality rate during childbirth (Puerperal Fever)

Nightingale

person: used statistics to show that typhus, poor food, and unsanitary conditions were killing soldiers

descriptive epidemiology

collecting all data that describe the occurrence of a disease, including info about those affected

• ex. Snow’s research on cholera

experimental epidemiology

use of experiments to test a hypothesis about a disease

• ex. Semmelweis’s research on Puerperal Fever

analytical epidemiology

comparison of a diseased group and a healthy group

• ex. Nightingale’s research on typhus