The study of disease
Study of the cause of disease
Development of disease
Colonization of the body by pathogens
An abnormal state in which the body is not functioning normally
Microorganisms that inhibit but do not cause disease in or on an organism under normal conditions.
May be present for days, weeks or months
one organism is benefited and the other is unaffected.
both organisms benefit
One organism is benefited at the expense of the other
Some normal microbiota are...
are opportunistic pathogens and can produce disease.
1. same microorganism (pathogen) must be present in every case of the disease.
2. must isolate the microorganisms from the diseased host and grow in pure culture.
3. The microorganism from the pure culture must produce the disease when inoculated into a susceptible host.
4. The microorganism must be recovered from the inoculated animal again in pure culture.
What did Koch's prove?
they proved certain organisms cause certain diseases.
Exceptions to Koch's postulates:
- Unique culture requirements
- Some diseases can cause several disease conditions
- Ethical consideration
Change in body function that is felt by the patient as a result of disease.
Change in a body that can be measured or observed as a result of disease.
Specific group of signs and symptoms that accompany a disease.
is spread from one host to another
is easily spread from one host to another
This is transmitted from one host to another.
fraction of a population that contracts a disease during a specific time
Fraction of a population having a specific disease at a given time.
disease that occurs occasionally in population
Disease constantly presented in a population
disease acquired by many hosts in a given area in a short time.
-Climate and weather
- Inherited traits such as the sickle- cell gene
Microorganism is present, but host is not showing any sign of the disease
short period of mild symptoms
Period of illness:
actual disease process
Period of decline:
sign and symptoms subside.
Period of Covalence:
person regains strength and body returns to the pre-
Pathogens limited to a small area of the body
An infection throughout the body.
System infection that began as an infection.
bacteria in the blood
growth of bacteria in the blood
toxins in the blood
viruses in the blood
Acute infection that causes the initial illness.
opportunistic infection after a primary (predisposing) infection.
no noticeable signs of symptoms (not apparent infection)
Transmission of Disease:
Contact (Transmission of disease)
-Direct: requires close association between infected and susceptible host
-Indirect: Spread by fomites
-Droplet: Transmission via airborne droplets
Vehicle (Transmission of disease)
Transmission by an inanimate reservoir (food, water, air)
Vectors (Transmission of disease)
-Arthropods: especially fleas, ticks and mosquitoes
-Mechanical: Arthropod carries pathogen on feet
-Biological: pathogen reproduces in vector
Are acquired as a result of a hospital stay
- 5-15% of all hospital patients acquire nosocomial infections
What are several factors of Nosocomial Infections?
-Microorganisms in the hospital environment
-The compromised status of the host
- The chain transmission in the hospital
Control of Nosocomial Infections:
-Control is difficult
The study of where and when diseases occur and how they are transmitted
-detective like work
-Collection of data
-Study case reports
incidence of a specific notifiable disease
deaths from notifiable diseases