Chapter 14 - Principles of Disease and Epidemiology

Dr. Schapiro - Exam 3

Human Microbiome

Begins to established in utero

• Vaginal Birth

  • Lactobacillus and Bacteroides

• Cesarean Birth

  • Microbiome resembles the human skin, Staphylococcus aureus

More microorganisms are acquired from food, people, and pets.

Remains throughout life

The distribution and composition of normal microbiota are determined by many factors

• Nutrients 

• Physical and Chemical Factors (lower pH in stomach)

• Host defenses (own immune systems so it don’t attack our own microbes)

• Mechanical Factors (microbes in our mouth with a lot of movement)Rrr

Human Microbiome Project

Analyzes relationships between microbial communities on the body and human health.

Normal Microbiota - permanently colonize the host and not cause disease under normal conditions.

Transient Microbiota - may be present for days, weeks, or months

Bold = Terms need to know for exam

Relationship Normal Microbiota vs Host

Microbial antagonism - competition between microbes

Normal Microbiota protect the host by:

1. Competing for nutrients - E. coli in our intestines competes with C.diff, which helps keep C.diff levels down and not overgrown.

2. Producing substances harmful to invading microbes

3. Affecting pH and available oxygen - keeping bacteria in place/where it’s supposed to be.

Symbiosis is the relationship between normal microbiota and the host

Some normal microbiota are opportunistic (potential to cause problems) pathogens.

⭐ - Example of an opportunistic pathogen causing infection?

Koch’s Postulates

links pathogens to the disease. Koch’s postulates are used to prove the cause of an infectious disease.

PATHOGEN CAUSES DISEASES

⭐ - What is the major significance of Koch’s work?
Microorganisms cause disease

Exceptions to Koch’s

1. Some pathogens can cause several disease conditions

2. Some pathogen cause disease only in humans

3. Some microbes have never been cultured

Predisposing factors

Makes the body more susceptible to disease.

1. Gender

2. Inherited traits, such as the sickle cell gene

3. Climate and weather

4. Age 

5. Life style

6. Nutrition

7. Chemotherapy

8. Lack of Vaccnation

9. Fatigue

Development of Disease

Incubation Period - interval between initial infection and first sign and symptom (slow increase, “3-4 days figure out if you have COVID”). It depends on the microorganism

Prodromal Period - short period after incubation; early mild symptoms

Period of Illness - disease is most severe (increasing very rapidly, your innate immune system at work, and then adaptive) White blood cell changes + Immune system

Period of Decline - signs and symptoms subside (decreasing rapidly) High risk of secondary infection

Period of Convalescence - body returns to its pre-diseased state (you feel fine, but there is still potential to pass it onto someone else) . People can serve as reservoirs during this time period

Epiemiology

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

Epidemiologists:

1. Determine the etiology (cause) of a disease

2. Identify other important factors concerning the spread of disease

3. Develop methods for controlling a disease

4. Assemble data and graphs to outline the incidence of disease

John Snow - Cholera in London

Occurrence of a Disease

Incidence - # of people who developed a disease during a particular time period (rate of new cases)

Prevalence - measures how much of a disease or condition there is in a population at a particular point in time. (both old and new cases)

CDC (Centers for Disease Control)

Collects and analyzes epidemiological information in the U.S

Publishes MMWR (Morbidity and Mortality Weekly Report)

Morbidity - incidence of a specific notifiable disease (everyone who got it)

Mortality - deaths from notifiable diseases (all deaths)

Notifiable Diseases - diseases in which physicians are required to report occurrence

Morbidity Rate - # of people affected in relation to the total population in a given time period.

Mortality Rate - # of deaths from a disease in relation to the population in a given time. 

Bacterial Infection #1

Headache and Joint Pain - Symptoms

Rash - Signs

Pathogen is the Cause of Infection/Disease

Not yet spread to other regions of the body - local infection

The bacterial infection is an example of - primary infection

Lyme - Disease

The doctor must report this case of Lyme disease because - notifiable infections disease

Tick latches on and breaks the skin of the host and transmits the bacteria; thus the tick is - vector 

The tick is transmitting the bacteria as a vector is an example of - biological transmission 

Well-established blacklegged tick populatuon is common throughout the northern United States. Thus Lyme disease is commonly observed - endemic 

Bacteria find their way into the bloodstream - sepsis 

Incorporating probiotics into the diet during the second course of antibiotics to help promote - normal microbiota

Reservoir of Infection

Continued sources of infection

Human Reservoirs

• Carriers may have inapparent infections or latent diseases'

Animal Reservoirs

• Zoonoses are diseases transmitted from animals to humans.

Nonliving Reservoirs

• Soil and Water

Healthcare-Associated Infections (HAIs)

Acquired while receiving treatment in a health care facility.

• Put all the weak people into 1 location , which makes it easier for pathogens to travel. You’re at a weaker state, which makes you susceptible — a compromised host

Compromised host - an individual whose resistance to infection is impaired by disease, therapy, or burns.

Bacterial Infection #2

Tetanus spreads through indirect contact transmission rather than person-to-person - a noncommunicative disease. 

Infection spreads throughout the body - systemic infection

Tetanus is - primary infection / acute disease

Once the primary infection begins to wane (period of decline) possibility to contract a - secondary infection (MRSA)

Viral Infection

spreads quickly from one individual to another - contagious disease

comes into contact with the fluid-filled blisters - direct contact transmission

coughs and sneezes - droplet transmission

gloves used when treating a patient and wearing a mask - standard precautions

Airborne and contact precautions - transmission-based precautions 

Viral infection in a pregnant woman and makes it into the mother’s bloodstream - viremia 

Potential to cross the placental barrier - congenital transmission

Impacting the normal development of vulnerable organs leading to - congenital varicella syndrome

An infection in which the causative agent is inactive for a time but then activates and produces symptoms is called a latent disease. 

A majority of children and adults have been vaccinated; reduced the spread infection from person to person since majority of the population is immune to the disease - herd immunity

As the incidence of disease decreases, chicken pox is now an example of - sporadic disease (NOT ENDEMIC) 

Emerging Infectious Disease

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

MOST ARE ZOONOTIC, of viral origin, and likely to be vector-borne

Contributing Factors to Emerging Infectious Disease

1. Genetic recombination

2. Evolution of new strains

3. Widespread use of antibiotics and pesticides

4. Changes in weather patterns

5. Modern transportation

6. Public Health Failure

7. Insect vectors

8. Ecological Disaster, war, and expanding human settlement

9. Animal Control Measures

⭐ Identify and explain 2 reasons why we are observing an increase in infectious diseases

Pathology

study of disease

Pathogen

organism that causes disease

etiology

cause of a disease

pathogenesis

development of disease

infection

invasion or colonization of the body by pathogens

disease

an abnormal state in which the body is not performing normal functions

symptoms

changes in body function that are felt by a patient as a result of disease

signs

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

syndrome

a specific group of signs and symptoms that accompany a disease

communicable disease

a disease that is spread from one host to another

noncommunicable disease

a disease that is not spread from one host to another

contagious disease

diseases that are easily and rapidly spread from one host to another

sporadic disease

disease that occurs only occasionally

endemic disease

disease constantly present in a population

epidemic disease

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

pandemic

worldwide epidemic

acute disease

Symptoms develop rapidly but disease lasts only a short time

chronic disease

symptoms develop slowly

subacute disease

intermediate between acute and chronic

latent disease

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

herd immunity

immunity in most of a population

local infection

pathogens are limited to a small area of the body

systemic (generalized) infection

an infection throughout the body

focal infection

systemic infection that began as a local infection

sepsis

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

bacteremia

bacteria in the blood

septicemia

also known as blood poisoning; growth of bacteriain the blood 

toxemia

toxins in the blood

viremia

viruses in the blood

primary infection

acute infection that causes the initial illness

secondary infection

opportunistic infection after a primary (predisposing) infection

subclinical disease

no noticeable signs or symptoms (inapparent infection)

direct contact transmission

requires close association between the infected and a susceptible host

congenital transmission

transmission from mother to fetus or newborn at birth

indirect contact transmission

spreads to a host by a nonliving object called a fomite

droplet transmission

transmission via airborne droplets less than 1 meter

vehicle transmission

airborne

waterborne

foodborne

vector

a living organism that transmits an infectious agent from an infected animal to a human or another animal

• arthropods like fleas, ticks, and mosquitoes

Transmits disease by 2 general methods

1. Mechanical - arthropod carries pathogen on its feet

2. Biological - pathogen reproduces in the vector; transmitted via bites of feces

Control of Healthcare-Associated Infections

Universal Precautions

• Standard precautions - basic, minimum practices

• Transmission-based precautions - supplemental to standard precautions; designed for known or suspected infections

  • Contact

  • Droplet

  • Airborne

Reduce # of pathogens by:

• Handwashing

• Disinfecting tubs used to bathe patients

• Cleaning instruments scrupulously

• Using disposable bandages and intubation

Infection control committees