Microbiology Chapter 9

Principles of Infectious Disease and Epidemiology

John Snow is considered one of the first modern epidemiologists. What did he do to gain this title?

dispelling the notion that illnesses were supernatural phenomena (bad air, evil spirits)

What is the difference between a true pathogen and an opportunistic pathogen?

T: does not require a weakened host to cause disease

O: only cause disease when host is weakened

Define host.

the organism targeted by a particular pathogen

What is the difference between sporadic vs endemic cases of infection?

S: isolated in a particular population

E: routinely detected in a population

What is the difference between disease distribution in an epidemic and vs pandemic? 

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

P: widespread disease outbreak in numerous countries

Knowing the difference in epidemic and pandemic, did the causative agent of COVID-19, SARS-CoV-2, cause an epidemic or pandemic? 

pandemic

What is the difference between an emerging pathogen and a remerging pathogen? 

E: pathogens caused only by sporadic cases, increasingly common

R: infectious agent that was under control due to prevention or treatment and is now resurfacing

What is a zoonotic disease?

spread from animals to humans

The current thinking is that SARS-CoV-2 was spread to humans from bats in Wuhan, China. What type of disease would this be?

zoonotic

What is the difference between noncommunicable and communicable diseases?

N: they do not spread from person to person

C: do transmit from human to human

What is the difference between signs and symptoms?

signs: objective indicators that can be measured or verified

symptoms: sensed by patient are are subjective

Is the following a sign or symptom: fever of 101°F

sign

Is the following a sign or symptom: rash on your body

sign

Is the following a sign or symptom: nausea

symptom

Is the following a sign or symptom: white blood cells in a urine sample

sign

Is the following a sign or symptom: fatigue

symptom

Is the following a sign or symptom: malaise

(general feeling of discomfort, illness) symptom

Why are Koch’s postulates important?

allowed us to identify the causative pathogen of many infectious diseases

Can Koch’s postulates elucidate all causative agents that cause disease in humans? Why or why not? 

no; they don’t apply/take into account to noninfectious diseases, obligate intracellular pathogens, human-specific pathogens, and latent infections

Why are obligate intracellular pathogens impossible to grow as independent pure cultures? 

they require a host cell to replicate

Define reservoir.

the animate or inanimate habitat where the pathogen is naturally found

Define source.

the animate or inanimate habitat which disseminates the agent from the reservoir to new hosts

What is the difference between endogenous vs exogenous sources? 

En: the pathogen came from the host’s own body

Ex: the pathogen came from an external source

Is the following direct contact or indirect contact spreading: zika virus infected mosquito bite

indirect

Is the following direct contact or indirect contact spreading: rabies infected dog bite

direct

Is the following direct contact or indirect contact spreading: eating contaminated food

indirect

Is the following direct contact or indirect contact spreading: gardening with an open wound on your hand

direct

Is the following direct contact or indirect contact spreading: sharing hepatitis-tainted hypodermic needles for drug use

indirect

Is the following direct contact or indirect contact spreading: breathing virus-contaminated aerosols from your friend’s cough

indirect

Is the following direct contact or indirect contact spreading: cockroaches running over your food

indirect

Is the following direct contact or indirect contact spreading: in utero transmission of HIV from mother to fetus

direct

Is the following direct contact or indirect contact spreading: kissing someone with mononucleosis

direct

Is the following direct contact or indirect contact spreading: unprotected sex with an HIV positive person

direct

Define vertical transmission of a pathogen. Know some examples

specialized direct contact, occurs when the pathogen passes from mother to offspring in utero, during birth, or postpartum (breast milk); HIV, syphilis, streptococci, gonorheal ophthalmia

What is an airborne transmission of a pathogen? How does it usually occur?

indirect. the pathogen enters through the respiratory route as it is inhaled; person-to-person, respiratory droplets

Define fomite.

an inanimate object or material that can carry and transfer infectious agents

Define vector.

organisms that spread infectious agents to hosts (arthropods and rodents)

What is the difference between biological and mechanical vectors? 

B: the vector organisms has a role in the pathogen’s life cycle

M: the vector spreads diseases without being integral to a pathogen’s life cycle

Define infectivity.

how good an infectious agent is at establishing an infection

Define pathogenicity.

the general ability of an infectious agent to cause disease

Define virulence.

the severity of disease following infection

List the 5 stages of infectious disease, briefly describe each one.

1. incubation period: time between infection and symptoms

2. prodromal phase: early symptom development

3. acute phase: peak

4. period of decline: replication of agent is under control, symptoms start to resolve

5. convalescent phase: patient recovers

During which of the 5 infectious disease stages can an infective agent be transmitted to a susceptible host? 

any of them

What is the difference between clinical (symptomatic) and subclinical (asymptomatic) cases? 

C: patient experiences full-blown classic symptoms of disease

S: infection fails to generate symptoms

What is the difference between chronic and asymptomatic carriers? 

C: a patient where the pathogen can exist in a dormant state and reactive later

A: patients who harbor certain pathogens for extended periods without experiencing symptoms

What are the two goals of epidemiology?

1. describe the nature, cause, and extent of new or existing diseases in populations

2. intervene to protect and improve health in populations

What is an etiological agent?

causative agent

What 3 parameters make up the epidemiological triangle?

environmental factors, host factors, and etiological agent

Define host range.

the type of host the pathogen can infect

What are 3 public health strategies implemented to break the epidemiological triangle? 

public education, quarantine, and vector control

Define quarantine.

a period of confinement away from population

How was the word Arbovirus derived?

arthropod-borne virus

What is one major role of the CDC?

serve as a central source of epidemiological information and public health recommendations

Define morbidity.

presence of a disease in a population

Define population.

any defined group of people

Define prevalence rate. 

measure of frequency that described morbidity in a given population during a specified time

Define incidence rate. 

frequency that expresses the number of new cases in a defined population during a defined time frame

Define mortality rate.

number of deaths during a specific time period

What does the acronym HAI stand for? What is another name for an HAI?

healthcare-acquired infections; nosocomial infections

What are the two most common sources that contribute to HAI transmission? 

contaminated medical devises and hands

According to the CDC, what are the 6 most common healthcare-acquired infections?

clostridioides difficile, ventilator-associated events, surgical site infections, catheter-associated urinary tract infections, central line-associated bloodstream infections, methicillin-resistant staphylococcus aureus bacteremia (MRSA)

Name 5 bacteria that are key HAI pathogens.

C. dill, E. coli, MRSA, pseudomonas aeruginosa, VRE,

List 4 viruses that are key HAI pathogens.

Hep. B, HIV, flu, viral gastroenteritis

Name 2 fungi that are key HAI pathogens.

aspergillus mold species, candida yeast species

What is one of the most important. yet simple and inexpensive measures overlooked for the prevention of HAIs?

proper hand washing

What is the difference between a reportable disease and a notifiable disease?

R: diseases on a state or local tracking list

N: diseases the CDC recommends reporting to government health agencies for monitering

Define disease eradication.

when there are no longer any cases of a disease anywhere in the world

What was the Tuskegee syphilis experiment?

looking at long-term affect of syphilis in a group of poor AA men, no cure existed, participants not informed they had the disease, misled

For most infective agents, what percentage of the population must be vaccinated for herd immunity to occur? 

85%

What disorder was incorrectly attributed to vaccination? 

autism