AH 3320 Q2: Epidemiology & Public Health

What is epidemiology?

Epidemiology = study of disease

What are the 3 factors epidemiologists study?

• Factors that determine:

  • Frequency

  • Distribution

  • Determinants of diseases

• In human populations

What is the difference between infection and disease?

Infection = condition in which microbes that cause disease have entered body

Disease = infection → damage cells, tissues, organs → signs & symptoms of illness

What are zoonotic diseases?

Zoonotic diseases = diseases human acquire from animal sources

What percentage of diseases are thought to originate in animals? Or what percentage of diseases are zoonotic?

>60% diseases originate in animals

Why are May, July, October, and December have the highest number of reported cases of Chlamydia AND Gonorrhea?

School break times = not busy doing other things

During what months does Anaplasma phagocytophilum peak?

Why?

July & August

• Transmitted through tick bites

What countries have greater concentrations of malaria?

Why?

Countries closer to equator

Malaria = transmitted through mosquitoes

Mosquitoes → longer seasons

What are the 7 most common modes of transmission of infectious diseases?

• Droplets = respiratory transmission

• Airborne = respiratory transmission

• Direct contact

• Indirect contact

• Waterborne

• Foodborne

• Vector-borne (insect bites)

What is the difference between communicable and contagious?

Communicable = ID transmitted from person to person (Ex. STI/STD)

Contagious = communicable disease = easily transmitted from person to person (Ex. Measles, Flu)

Ex. STI vs. Influenza

• Both diseases are communicable but only one is contagious (easily transmitted)

What is incidence?

Incidence = # of new cases of particular disease in defined population during specific time period

What is a morbidity rate?

Morbidity rate = # of new cases of particular cases that occurred during a specified time period per specifically defined population

• Usually 100,000 population

What is the difference between period prevalence and point prevalence?

Period prevalence = # of ALL cases (not only new) of disease existing in given population during specific time period (1988 or 2020 or 1988-2020)

Point prevalence = Total # of cases (not only new) of disease existing in given population @ a specific time (Ex. right now)

Refer to this model to study epidemiology terminology

Mortality or Cure = only way to leave prevalence pool

Recurrence = reenter prevalence pool

What is the mortality rate?

Mortality rate = ratio of # of people who died of particular disease during specified time period per specified population (usually 100,000)

What is sporadic disease?

Sporadic disease = occurs only occasionally within population @ particular geographic area (Ex. human plague)

What is endemic disease?

Endemic disease = always present within population of particular geographic area (Ex. common cold)

What country and region is the Ebola virus endemic to?

Democratic Republic of Congo + Sub-Saharan Africa

What continents did Ebola outbreak occur?

North America, Africa, Europe, Asia → included non-endemic regions

What is epidemic disease?

Epidemic diseases = a greater than usual # of cases of disease in particular region (usually in short period of time)

What is polio?

What mode is it transmitted through?

Polio = enterovirus from intestinal contents of animal = infect digestive tract

Fecal-oral route

How is polio prevented?

How was polio eradicated in certain countries?

Polio vaccination

2nd dose recommended → polio eradicated

How do vaccines work?

How can vaccine-derived poliovirus occur?

Vaccines = attenuated virus (DEAD) = cannot cause disease → expose immune system → develop immune response → produce antibodies

• Prime immune system to react to virus

• May get sick, but not as sick

Vaccine-derived poliovirus can occur if a LIVE viruses in vaccines are injected

12 people at a picnic get food poisoning. Is this an example of an epidemic disease?

YES - 12 people = higher than usual # of cases of disease in particular region, usually within a short amount of time

What is food poisoning classified as?

Food-borne intoxication = ingested toxins produced by Staphylococcus aureus

Microbial Intoxication

What is a pandemic?

How do they differ from epidemic diseases?

Pandemic = disease that occurring in epidemic proportions in many countries simultaneously

Epidemic = greater than usual # of cases of a disease in particular region, usually within short period of time

What are 5 examples of pandemics?

1. COVID-19

2. Spanish Flu (1918) → 20 Million deaths

3. Swine Flu (2009) → 18,000 deaths, <5000 U.S. Deaths

4. Chikungunya Pandemic

5. Zika Virus Pandemic

What is the deadliest pandemic in history?

How many deaths did it result in?

What proportion of the European population did it kill?

What group did it hit the hardest and why?

Bubonic Plague or Black Death

200 Million people

Killed 1/3 of population in Europe

City dwellers → overcrowding & lack of sanitation

What is the causative organism of the bubonic plague?

Gram stain negative or positive?

Yersinia pestis bacteria

Flea bite rats → rats bite people → spread of plague

Gram stain negative