chapter 11 - principles of disease and epidemiology pathologystudy of disease etiologystudy of the...

Chapter 11 - Principles of Disease and Epidemiology

• Pathology Study of disease

• Etiology Study of the cause of a disease

• Pathogenesis Development of disease

• Infection Colonization of the body by pathogens

• Disease An abnormal state in which the body is not functioning normally

• Transient microbiota may be present for days, weeks, or months

• Normal microbiota permanently colonize the host

• Symbiosis is the relationship between normal microbiota and the host

Normal Microbiota and the Host

• In one organism is benefited and the other is unaffected.

• In both organisms benefit.

• i.e. E. coli produces vitamin K (and some B)

• In parasitism, one organism is benefited at the expense of the other.

Normal Microbiota and the Host:

Figure 14.2

• Locations of normal microbiota on and in the human body


• Microbial antagonism is competition between microbes.

• Normal microbiota protect the host by:

• occupying niches that pathogens might occupy

• producing acids

• producing bacteriocins



• Some normal microbiota are opportunistic pathogens.

• (vaginal yeast infection)

• Normal location: vagina, mouth

• (urinary tract infections)

• Normal location: large intestine

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings


• (hospital acquired diarrhea; may cause pseudomembranous colitis)

• Normal location: large intestine

• (a major cause of meningitis)

• Normal location: nasopharynx

• are live microbes applied to or ingested into the body, intended to exert a beneficial effect.

• are chemicals used to promote growth of beneficial microbiota

Classifying Infectious Diseases

• Symptom A change in body function that is felt by a patient as a result of disease

• Sign A change in body function that can be measured or observed as a result of disease.

• Syndrome A specific group of signs and symptoms that accompany a disease.

Classifying Infectious Diseases

• Communicable disease A disease that can be spread from one host to another.

• Contagious disease A disease that is easily spread from one host to another.

• Noncommunicable disease A disease that is not transmitted from one

host to another.

• i.e. Chicken pox, measles, common cold are contagious

• i.e. Tetanus, Anthrax are noncommunicable

• Incidence Number of new cases of a disease during a specific time period.

• Prevalence Total number of old and new cases of a disease during a specific time period.

• Sporadic disease Disease that occurs occasionally in a population.

• i.e. Eastern Equine Encephalitis

Occurrence of Disease

Occurrence of Disease• Disease constantly present in a

population. i.e. common cold

• Epidemic disease Disease acquired by many hosts in a given area in a short

time. i.e. influenza,

• Pandemic disease Worldwide epidemic. i.e. influenza; AIDS

• Immunity in most of a population.

• Acute disease Symptoms develop rapidly, but last a short time. i.e. influenza, cold

• Chronic disease Disease develops slowly, lasts a long time. i.e.

Hepatitis B

• Subacute disease Symptoms between acute and chronic. i.e. gingivitis

• Latent disease Disease with a period of no symptoms when the “microbe”

is inactive. i.e. genital herpes,

Severity or Duration of a Disease

• Local infection Pathogens limited to a specific area of the body. i.e.

pulmonary Tuberculosis; Strep throat

• Systemic infection An infection throughout the body.

• Focal infection Systemic infection that began as a local infection.

i.e. Tuberculosis; Tetanus

• Bacteremia Bacteria in the blood

• Septicemia Growth of bacteria in the blood

Extent of Host Involvement

• Toxemia Toxins in the blood

• Viremia Viruses in the blood

• Primary infection Infection that causes the initial illness; often acute

•

• Secondary infection Opportunistic infection after a primary (predisposing) infection

Extent of Host Involvement

The Stages of a Disease

Figure 14.5

• Reservoirs of infection are the primary receptacles of the infectious agent. They may or may not be the direct source of the infection.

• Animal

• dogs, bats, racoons, foxes, other mammals

• Rocky Mountain Spotted Fever: ticks

• soil, infected cows, sheep, other animals

• may be transmitted to humans

Reservoirs of Infection


Reservoirs of Infection

• Human — HIV, gonorrhea

• Carriers may have inapparent infections or latent diseases

• Nonliving —

• Soil: Botulism (Clostridium botulinum), Tetanus (Clostridium tetani)

• Water: Cholera (Vibrio cholerae)

• Food: Tapeworm

• Contact

• Direct Requires physical contact between infected and susceptible host

• Indirect Spread by

• Droplet Transmission via airborne droplets; usually travel less than one

meter

Transmission of Disease


PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

Microbiology

B.E Pruitt & Jane J. Stein

AN INTRODUCTIONEIGHTH EDITION

TORTORA • FUNKE • CASE

• Vehicle Transmission by an inanimate reservoir (food, water, air)

• Vectors Insects, especially fleas, ticks, and mosquitoes

• Insect carries pathogen on feet.

• Pathogen reproduces in vector. i.e. Malaria, Rocky

Mountain Spotted Fever disease

Transmission of Disease



Microbiology




Figure 14.7, 9

• Are acquired as a result of a hospital stay

• 5-15% of all hospital patients acquire nosocomial infections

• A leading cause of death in U.S.

Nosocomial (Hospital-Acquired) Infections


Relative frequency of nosocomial infections


Common Causes of Nosocomial Infections

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

• Contributing factors:

• Evolution of new strains

•

• Inappropriate use of antibiotics and pesticides

• Antibiotic/pesticide resistant strains

• Changes in weather patterns (and global warming?)

• (and malaria)

Emerging Infectious Diseases

http://wwwnc.cdc.gov/eid/pages/background-goals.htm

• Contributing factors:

• Modern transportation

•

• Ecological disaster, war, expanding human settlement

• Ebola

• Animal control measures

•

• Public Health failure

• Diphtheria

Emerging Infectious Diseases

http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/ebolatable.htm

• The study of where and when diseases occur

• How they’re transmitted

• How many infected

Epidemiology

Figure 14.11

EpidemiologyJohn Snow 1848-1849 Mapped the occurrence of

cholera in London

Ignaz Semmelweis 1846-1848 Showed that hand washing decreased the incidence of puerperal fever

Florence Nightingale 1858 Showed that improved sanitation decreased the incidence of epidemic typhus; backed by statistics

• Descriptive Collection and analysis of data regarding occurrence of disease

Snow

• Analytical Comparison of two different diseased groups OR diseased and healthy groups

Nightingale

• Experimental Study of a disease using controlled experiments

Semmelweis

• Case reporting Health care workers report specified disease to local, state, and national offices

• Nationally Notifiable Diseases

Physicians are required to report occurrence



Microbiology




Table 14.7

• Collects and analyzes epidemiological information in the U.S.

• Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov

• Morbidity: incidence of a disease

• Mortality: death from disease

Centers for Disease Control and Prevention (CDC)

http://cdc.gov/mmwr

http://cdc.gov/

http://cdc.gov/

chapter 11 - principles of disease and epidemiology pathologystudy of disease etiologystudy of the...

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