Chapter 9: Exam 2

Disease

Disease

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

Pathology

the study of disease

Etiology

the cause of a disease

Pathogenesis

the development of disease

Epidemiology

is the monitoring and controlling disease occurrence to promote public health

Pathogen

microorganism that creates a disease

Infection

invasion or colonization of the body by pathogens

infectious disease

is an illness caused by a pathogen

Helminths (parasitic worms)

hookworm, pinworm, trichinosis, schistosomiasis (eukaryotic multicellular animal)

Protozoan (animal-like protists)

Giardiasis, malaria, toxoplasmosis (eukaryotic unicellular parasites)

Fungi

histoplasmosis, athlete's foot (tinea pedis)

bacteria

prokaryotic unicellular; some are obligate intracellular parasites, which other are fee living; usually smaller than eukaryotic cells (streptococcal infections, staphylococcal infections, bacterial pneumonia, tetanus, chlamydia. tuberculosis, typhus, whooping cough (pertussis) plague

viruses

not cells; infectious particles containing nucleic acids ( DNA or RNA genome); usually smaller than prokaryotic cells (chickenpox, measles, AIDS, rabies, influenza, cold, polio, smallpox, herpes, hepatitis

Prions

infectious proteins (not cells); do not contain DNA or RNA; can cause certain proteins in host brain to fold incorrectly ( the human analog of "mad cow disease")

opportunistic pathogens

only cause disease when their host is weakened (e.g., weak immune system)

true pathogen

does not require a weakened host to cause disease (makes everyone sick)

sporadic cases

a disease are isolated infections in a particular population (ebola)

endemic infections

are routinely detected in population or region (head colds)

epidemic

a widespread disease outbreak in a particular region during a specific time frame

pandemic

occurs if an epidemic spreads to numerous countries

emerging pathogens

included newly identified agents as well as pathogens that previously caused only sporadic cases (COVID-19, Zika)

reemerging pathogen

an infectious agent that was under control but is now surfacing (antibiotic resistance bacteria)

Zoonotic diseases

spread from animals to humans- (many are noncommunicable)

communicable diseases

transmit from human to human

contagious diseases

easily transmitted from one host to the next

signs

objective indicators of disease that can be measured or verified (fever, rash or blood in stool)

symptoms

are sensed by the patients and are subjective rather than precisely measurable (pain, fatigue, and nausea)

latent infection

usually asymptomatic ( no signs or symptoms)

Acute disease

have a rapid onset and progression

chronic disease

slower onset and progression

reservoirs

are an animate or inanimate habitat where the pathogen is naturally found

sources

disseminate infectious agent from the reservoir to new hosts

endogenous source

the pathogen came from the host's own body

exogenous source

the pathogen is external to the host; (environmental- contaminated food, animals-transmit zoonotic disease to people, humans-transmit communicable infections from one person to another)

misplaced normal microbiota

bacteria living harmlessly on the skin can enter surgical incisions to cause postoperative infections

disrupted microbiota and opportunistic pathogens

yeast in the vagina may proliferate and cause infection after antibiotics kill off bacterial neighbors

modes of transmission

how the pathogen spreads to a host

direct contact transmission

between source of pathogen and host

indirect contact transmission

no direct contact between the source of pathogen and host

vertical transmission (direct)

occurs when the pathogen passes from mother to offspring during; pregnancy, delivery, breast feeding

airborne transmission (indirect)

the pathogen enters through the respiratory route; usually occurs by inhaling pathogen-laden respiratory droplets

vehicle transmission (indirect)

pathogen is found on contaminated fomite (doorknobs, needles, sheets, food)

vector transmission (indirect)

transmission by vectors (arthropods)

biological vector (indirect)

vector organism has a role in the pathogens life cycle (ticks, mosquitos)

mechanical vector (indirect)

vector spreads disease without being integral to the pathogen's life cycle (flies, rodent, and cockroaches)

infectivity

describes how good an infectious agent is at establishing an infection

virulence

describes severity of disease following infection

pathogenicity

the general ability of an infectious agent to cause disease

infectious agent

how many/much of a pathogen have to be in contact with something to become sick

what are the five general stages of disease that occurs during infection?

1. incubation period

2. prodromal period

3. acute phase

4. period of decline

5. convalescent phase

incubation period

the period between infection and the development of the earliest symptoms

prodromal phase

early symptoms develop- start to feel run down and may have mild symptoms

acute phase

the peak of the disease; full-blown classical symptoms of the disease; known as a symptomatic case ( or a clinical infection)

asymptomatic case (subclinical case)

symptoms are mild or nonexistent; prodromal and acute phase go unnoticed

period of decline

pathogen replication decreases; patient begins to feel better

convalescent period

elimination of the pathogen from the body