Microbio ch 16 tcc SE Dr. Brookins

Epidemiology

study of disease in populations

John Snow

father of epidemiology; traced the 1854 Broad Street cholera outbreak to a contaminated water pump

Fecal-oral route

how cholera spreads (contaminated water)

Incidence

number of NEW cases in an area over a period of time

Prevalence

number of TOTAL cases (old and new) in an area over a period of time

Morbidity

number of people ill with a disease

Mortality

number of deaths from a disease

Index case

first documented case of a disease in a population

Endemic

constantly present in a population at a low level (example: malaria in Brazil)

Sporadic

random unpredictable cases (examples: tetanus; rabies; plague)

Outbreak

sudden rise in cases of a disease

Epidemic

sudden increase in cases above what is expected in a region (example: influenza)

Pandemic

epidemic that spreads worldwide

Common source spread

all cases come from one source (example: contaminated water or food)

Point source spread

common source that acts for a short time (example: one bad potato salad)

Continuous common source spread

common source that acts for a long time

Intermittent common source spread

common source that starts and stops and starts again

Propagated spread

person-to-person spread; each case infects others

Etiologic agent

the pathogen that causes a disease

Reservoir

place where an infectious agent lives and persists

Asymptomatic Carrier

person who spreads a pathogen without showing symptoms

Passive carrier

contaminated with the pathogen but not infected (example: unwashed hands)

Active carrier

infected person who can spread the disease

Asymptomatic carrier

infected person with no symptoms (examples: hepatitis B; herpes simplex; HIV; Salmonella typhi)

Typhoid Mary

Mary Mallon; asymptomatic carrier of Salmonella typhi who was a cook

Zoonotic reservoir

animal that can pass an infection to humans (examples: avian flu; anthrax)

Definitive host

host where a parasite reaches sexual maturity

Intermediate host

host where a parasite develops immature stages

Vertical transmission

parent to offspring

Transplacental transmission

vertical transmission across the placenta

Parturition transmission

vertical transmission during birth

Direct horizontal transmission

person-to-person by contact or droplets or aerosols

Droplet transmission

spread by coughing or sneezing or talking within about 1 m

Airborne transmission

spread by particles that travel farther than 1 m

Indirect (vehicle) transmission

spread by nonliving carriers

Fomite

nonliving object that carries a pathogen (example: contaminated surface)

Vehicles of transmission

airborne; waterborne; fecal-oral; foodborne

Vector

living organism that carries a pathogen between hosts (usually arthropods)

Biological vector

pathogen completes part of its life cycle in the vector (example: tick)

Mechanical vector

carries pathogen passively on its body parts (example: fly feet)

Black fly

vector for Onchocerca volvulus (river blindness)

Flea

vector for Rickettsia typhi (murine typhus) and Yersinia pestis (plague)

Kissing bug

vector for Trypanosoma cruzi (Chagas disease)

Louse

vector for Bartonella quintana (trench fever) and Borrelia recurrentis (relapsing fever) and Rickettsia prowazekii (typhus)

Mite (chigger)

vector for Orientia tsutsugamushi (scrub typhus) and Rickettsia akari (rickettsialpox)

Mosquito

vector for yellow fever virus and Plasmodium falciparum (malaria) and West Nile virus

Sand fly

vector for Leishmania (leishmaniasis)

Tick

vector for Borrelia (Lyme disease) and Rickettsia rickettsii (Rocky Mountain spotted fever)

Tsetse fly

vector for Trypanosoma brucei (African sleeping sickness)

Rocky Mountain spotted fever

caused by Rickettsia rickettsii; spread by a tick (biological vector)

Nosocomial infection

infection acquired in a healthcare setting

Common nosocomial infections

urinary tract; surgical wound; respiratory

Cause of nosocomial infections

lack of infection control (example: poor hand hygiene)

Endogenous nosocomial infection

from the patient's own normal microbiota

Exogenous nosocomial infection

pathogen acquired from the healthcare environment

Iatrogenic nosocomial infection

result of a medical procedure

MRSA

methicillin-resistant Staphylococcus aureus; common cause of nosocomial sepsis

Standard precautions

CDC guidelines to reduce disease transmission: hand hygiene; PPE; respiratory hygiene; safe needle use; isolation; sterilizing instruments; cleaning surfaces

Isolation

separating sick people from healthy people

Quarantine

separating exposed people to see if they get sick

Immunization

vaccination to build immunity

Herd immunity

protection of susceptible people when most of a population is immune

Vector control

reducing the vector population (example: mosquito control)

CDC

Centers for Disease Control and Prevention; U.S. disease prevention and outbreak control

WHO

World Health Organization; global health collaboration

Notifiable diseases

diseases that must be reported to public health authorities

MMWR

Morbidity and Mortality Weekly Report; tracks over 50 notifiable diseases

Risk factors for infectious disease

drug resistance; anti-vaccination movement; emerging diseases; reemerging diseases

Barriers to eradicating infectious disease

healthcare access; microbe evolution; social conditions; immigration and travel

Emerging disease

new to humans or increasing in the past 20 years

Reemerging disease

increasing again after a period of decline

Technology and disease spread

air travel (SARS-CoV-2; influenza; Ebola; Zika); blood banks (HIV; hepatitis C; Babesia); habitat loss (Lyme disease)

Influenza pandemics

1918 (40-50 million deaths); 1957; 1968; 2009; caused by influenza virus

Bubonic plague pandemics

caused by Yersinia pestis; Black Death 1347-1351

Cholera pandemics

caused by Vibrio cholerae; seven pandemics

AIDS

caused by HIV; since 1981; over 25 million deaths

COVID-19

caused by SARS-CoV-2; pandemic since 2019

Which best describes an index case?

the first documented case of a disease in a population (multiple choice question, not definition)

Which term is the number of new cases over a specific period?

incidence

Common cause of nosocomial infections?

poor hand hygiene in healthcare settings

Which disease is constantly present at a low predictable rate?

endemic

Primary role of the CDC?

set guidelines for disease prevention and quarantine and outbreak control in the U.S.

Example of indirect contact transmission?

contaminated surfaces (fomites)