Bio251a: Chapter 13 Microbe-Human Interactions Infection, Disease, and Epidemiology [part two]

What are the 4 distinct stages of clinical infections?

Incubation period, Prodromal stage, Period of invasion, Convalescent period

What occurs during Incubation period?

time from initial contact with the

infectious agent to the appearance of first symptoms; agent is multiplying but damage is insufficient to cause symptoms

How long does incubation period last?

several hours to several years

What occurs during Prodromal stage?

vague feelings of discomfort; nonspecific complaints

What occurs during period of invasion?

multiplies at high levels, becomes well-established; more specific signs and symptoms

What occurs during Convalescent period?

as person begins to respond tothe infection, symptoms decline

What are the different Patterns of Infection? (6)

Localized infection, Systemic infection, Focal infection, Mixed infection, Primary infection, Secondary infection, Acute infection, Chronic infections

What occurs during Localized infection?

microbes enter the body and remains confined to a specific tissue

What occurs during systemic infection?

infection spreads to several sites and tissue fluids usually in the bloodstream

What occurs during Focal infection?

when infectious agent breaks loose

from a local infection and is carried to other tissues

What occurs during Mixed infection?

"polymicrobial"; several microbes grow simultaneously

at the infection site

What is Primary infection?

initial infection

What is Secondary infection?

another infection by a different microbe

What is Acute infection?

comes on rapidly, with severe but short-lived effects

What is an example of acute infection? Explain

Common cold

• Symptoms begin 2-3 days after contact

• Resolve by ~ 10 days without therapy

What is common cold most commonly caused by?

rhinovirus

What are Chronic infections?

progress and persist over a long period of time

What is an example of Chronic infections? Explain

Cold sores- Herpes simplex virus- type 2

• Periods of infection and latency

Which is the state of infection when a person is most symptomatic?

Period of invasion

What are the earliest symptoms of disease? Why do they occur?

Fever, pain, soreness, swelling; SIGN OF INFLAMMATION result of the activation of the body defenses

What are signs of inflammation?

Edema, Granulomas and abscesses, Lymphadenitis

What is edema?

accumulation of fluid

What are Granulomas and abscesses?

walled-off collections of inflammatory cells and microbes

What is Lymphadenitis?

swollen lymph nodes

What are Signs of Infection in the Blood?

Changes in the number of circulating white blood cells

What are types of changes in the number of circulating white blood cells?

Leukocytosis, Leukopenia, Septicemia, Bacteremia, Viremia

What is Leukocytosis?

increase in white blood cells

What is Leukopenia?

decrease in white blood cells

What is Septicemia?

microorganisms are multiplying in the blood and present in large numbers

What is Bacteremia?

small numbers of bacteria present in blood not necessarily multiplying

What is Viremia?

small number of viruses present not necessarily multiplying

What are Asymptomatic/subclinical infections?

although infected, the host doesn't show any signs of disease

What occurs in result of Inapparent infection?

no signs or symptoms so person doesn't seek medical attention

What are Portals of Exit?

Pathogens depart by a specific avenue; greatly influences the dissemination of infection

What are the Portals of Exit?

Respiratory, Skin scales, Fecal exit, Urogenital tract, Removal of blood

What components are included in the respiratory portal exit?

mucus, sputum, nasal drainage, saliva

Does recovering from illness mean that microbe is removed?

no

What are the components of Persistence of Microbes and

Pathologic Conditions?

Latency, Chronic carrier, Sequelae

What is latency?

infection in which the pathogen is not active or causes disease

What is Chronic carrier?

person with a latent infection who sheds the infectious agent

What is Sequelae?

long-term or permanent damage totissues or organs

What are two types of Sources and Transmission of Microbes?

Reservoir, Source

What is reservoir?

primary habitat of pathogen in the natural world; Human or animal carrier, soil, water, plants

What is an example of Reservoir? explain

Influenza virus, the reservoir is birds since they can harbor the virus without showing signs of infection

What is Source?

individual or object from which an infection is actually acquired

What is an example of source? explain

Door knob, roommate, two year old daughter

What is a Living Reservoir called?

carrier

What is a carrier?

an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to the microbe

What is an Asymptomatic carrier?

shows no symptoms

What is a passive carrier?

contaminated healthcare provider picks up pathogens and transfers them to other patients

How can health care workers be passive carriers?

Carries the pathogen on their skin or a fomite (an inanimate object) that can transport a pathogen.

- Ex: ties, mops, blankets,

clothing, stethoscope.

What are Incubation carriers?

spread the infectious agent during the incubation period

What are Convalescent carriers?

recuperating without symptoms

What are Chronic carriers?

individual who shelters the infectious

agent for a long period

What is the progression for Living Reservoir carriers?

1.) Asymptomatic carrier

2.) Incubation carriers

3.) Convalescent carriers

4.) Chronic carrier

If a nurse transfers a pathogen between patients without becoming infected herself, the nurse as acted as the

Passive Carrier

What are the two Acquisition and Transmission of Infectious Agents?

Communicable disease and Non-communicable infectious disease

What is Communicable disease?

when an infected host

can transmit the infectious agent to another host

and establish infection in that host

What type of communicable disease is contagious?

Highly communicable diseases; direct contact

What is non-communicable disease?

does not arise through transmission from host to host; Contact with organism (facultative parasites,

fungal/bacterial spores) in natural, non-living reservoir

When does non-communicable disease usually occur?

when a compromised person is invaded by his or her own normal microflora

What are the two Patterns of Transmission?

direct contact and indirect contact

What is direct contact?

physical contact or fine aerosol droplets

What is indirect contact?

passes from infected host to intermediate conveyor and then to another host

What is vehicle?

inanimate material, food, water, biological products, fomites

What is airborne?

droplet nuclei, aerosols

How is direct infectious disease acquired?

- contact; kissing. sex

- droplets; colds, chickenpox

- vertical; HIV, syphillis

- biological vector; west nile virus, malaria

How is indirect infectious disease acquired?

- fomites; staphylococcus

- food/water/biological products; salmonella, e. coli

- air; tuberculosis, influenza virus, hantavirus

What are Nosocomial Infections?

Diseases that are

acquired or developed

during a hospital stay

How do Nosocomial Infections occur in the hospital?

From surgical procedures, equipment, personnel, and exposure to drug-resistant microorganisms

How many cases and deaths are there due to Nosocomial Infections in the US?

2 to 4 million cases/year in U.S.with approximately 90,000 deaths

What is Epidemiology?

describe Frequency of Cases

What is Prevalence?

total number of existing cases with respect to the entire population usually represented by a percentage of the population

What is Incidence?

measures the number of new cases over a certain time period, as compared with the general healthy population

What is Mortality rate?

the total number of deaths in a population due to a certain disease

What is Morbidity rate?

number of people afflicted with a certain disease

What is Endemic?

disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale

What is Sporadic?

when occasional cases are reported at irregular intervals

What is Epidemic?

when prevalence ofa disease is increasing beyond what is expected

What is Pandemic?

epidemic across continents

What is the function of Koch's Postulates?

Determining the causative agent of a disease

What are the steps of Koch's Postulates?

1. Find evidence of a particular

microbe in every case of a

disease

2. Isolate that microbe from an

infected subject and cultivate it

artificially in the laboratory

3. Inoculate a susceptible healthy

subject with the laboratory

isolate and observe the

resultant disease

4. Reisolate the agent from this

subject