Epidemiology (Chapter 14)

Pathology

the study of disease

Etiology

the cause of a disease

Infection

invasion or colonization of the body by pathogens

Infectious disease

occurs when an infection results in any

change in the state of health

Normal microbiota protect the host by:

– Competing with invading microbes for nutrients

– Producing substances harmful to invading microbes

– Affecting pH and available oxygen

Symptoms

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

-Not apparent to an observer

Signs

objective changes in a body that can be

measured or observed as a result of disease

Syndrome

specific group of signs and symptoms that

accompany a disease

Communicable disease

a disease that is spread from one host to another

–Examples: COVID-19, chicken pox, measles, influenza, genital herpes, tuberculosis

Contagious diseases

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

Noncommunicable disease

a disease that is not spread from one host to another

– Example: tetanus

Incidence

number of people who develop a disease

during a particular time period

Prevalence

-number of people who have a disease at a specified time, regardless of when it first appeared

-Takes into account both old and new cases

Sporadic disease

disease that occurs only occasionally

Endemic disease

disease constantly present in a population

Epidemic

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

Pandemic disease

worldwide epidemic

Acute disease

symptoms develop rapidly but has a short

duration

Chronic disease

symptoms develop slowly, likely to last for a

long period

Subacute disease

intermediate between acute and chronic

Latent disease

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

Infection fatality ratio (IFR)

divide the number of deaths attributed to a disease by the total number of infected individuals within a specific time period

– The lower the IFR, the lower the number of fatalities

Case fatality ratio (CFR)

proportion of individuals diagnosed with a disease who die from that disease within a certain period of time

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 bacteria in the blood; bacteria are proliferating in the blood

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

transmission by an inanimate reservoir like water, air, food