chapter 9 microbio

epidemiology

study of the distribution and determinants of health related states or events in specified populations, and the application of this study to control of health problems.

what was john snows’ contribution to science?

Dispel notions of illnesses being regarded as supernatural phenomena- the work of “bad air” or “evil spirits.” Considered one of the first modern epidemiologists. He also located public well in London as likely origin of a cholera outbreak. 

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

A true pathogen does not require a weakened host to cause disease. Opportunistic pathogens tend to only cause disease when their host, the targeted organism, is weakened in some way- often through shifts in the normal microbiota or weakening of the immune system.

Define host. 

The organism targeted by a particular pathogen 

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

Sporadic describes a disease that causes occasional infections in a population. Endemic describes infections that are routinely detected in a population or region. 

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

 epidemic is a widespread disease outbreak in a particular region during a specific time frame. A pandemic is when an epidemic spreads to numerous countries

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

Pandemic

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

Emerging pathogens are pathogens that previously caused only sporadic cases but are increasingly common and/or exhibit an expanded geographical distribution; cause emerging diseases. Reemerging pathogen is an infectious agent that was under control due to prevention or treatment strategies and is now resurfacing. 

What is a zoonotic disease?

Disease that spreads from animals to humans. Many are noncommunicable, meaning they do not spread from person to person, but they can mutate into communicable forms that do.

What is the difference between noncommunicable and communicable diseases?

Noncommunicable: do not spread from person to person. Communicable: does spread from person to person

What is the difference between signs and symptoms? 

Signs are objective indicators or disease that can be measured or verified; common signs include fever, rash, or blood in stool. Symptoms are indicators of disease that are sensed by the patient and are subjective rather than precisely measurable; pain, fatigue, and nausea are examples. 

which are signs and which are symptoms

signs: fever of 101 degree f, rash on body, white blood ccells in a urine sample

symptoms: nausea, fatigue, malaise (discomfort)

Why are Koch’s postulates important?

They allowed us to identify the causative pathogens of many infectious diseases

can koch’s postulates elucidate all causative agents that cause disease in humans? why or why not?

They do not apply to noninfectious diseases because those illnesses are not directly caused by pathogens

reservoir

the animate or inanimate habitat where a pathogen is naturally found

source

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

What is the difference between endogenous vs exogenous sources? NOTE: the prefix “endo-” means “within” or “inner” and the prefix “exo-“ means “exterior” or “external”. Knowing this will help you remember these terms.

Endogenous: a scenario where the pathogen comes from the host’s own body. Exogenous: a source of an infecting pathogen that is external to the host 

The mode of transmission is how the pathogen spreads to the host. There are two main types of transmission: direct contact and indirect contact. Determine if the following are examples of direct or indirect contact transmission.

-Zika virus infected mosquito bite (indirect)

-Rabies infected dog bite  (direct)

-Eating contaminated food  (indirect)

-Gardening with an open wound on your hand (direct)

-Sharing hepatitis-tainted hypodermic needles for drug use (indirect)

-Breathing virus-contaminated aerosols from your friend’s cough (indirect)

-Cockroaches running over food (yuck!) (indirect)

-in utero transmission of HIV from mother to fetus (direct)

-Kissing a person who has mononucleosis (direct)

-Unprotected sex with an HIV positive person (direct)

 Define vertical transmission of a pathogen. Know some examples

A specialized form of direct contact transmission that occurs when the pathogen passes from mother to offspring during pregnancy (in utero), during delivery (transcervical), or through breast milk (postpartum). Example: HIV

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

A type of indirect contact transmission in which the pathogen enters through the respiratory route as it is inhaled. Usually occurs by inhaling pathogen-laden respiratory droplet and/or finer aerosols

formite define

Fomite transmission is another name for vehicle transmission; transmission of an infectious disease by an inanimate object (fomite)

vector

Organisms such as arthropods and rodents that spread infectious agents to other susceptible hosts

What is the difference between biological and mechanical vectors? 

Biological: vector organisms that have a role in the pathogen’s life cycle; common examples are ticks and mosquitos.

Mechanical: vector organism that spreads disease without being integral to a pathogen’s life cycle

Define infectivity

Term describing how good an infectious agent is at establishing an infection

Define pathogenicity.

A term describing the general ability of an infectious agent to cause disease 

Define virulence

Term describing severity of disease following infection; degree or extent of disease that a pathogen causes. 

Use the information in Figure 9.2 Five stages of infectious disease, to answer the following: List the five stages of infectious disease, and briefly describe each stage. 

1. incubation period: time between infection and the development of the earliest symptoms

2. prodromal phase: early symptoms develop

3. acute phase: the peak of the disease

4. period of decline: replication of the infectious agent is brought under control; symptoms start to resolve

5. convalescent phase: the patient recovers; in some cases, the pathogen is kept latent in the patient. 

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

prodromal

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

 Symptomatic: a case of infection in which a patient experiences the full-blown classical symptoms of the disease; also called a clinical infection.

Asymptomatic case: an infection that fails to generate symptoms; also called subclinical phase 

What is the difference between chronic and asymptomatic carriers?

Chronic: a patient in whom the pathogen can exist in a dormant (or latent) state and reactivate later; a chronic carrier patient may remain asymptomatic for long periods, only to have symptoms reemerge from time to time; even when chronic carriers are asymptomatic, they may infect others.

Asymptomatic carriers: individuals who harbor certain pathogens for extended periods without experiencing symptoms. 

 What are the two goals of epidemiology?

Aims to understand and prevent illness in communities 

What is an etiological agent?

causative agent

Use the information in Figure 9.4 Epidemiological triangle to answer the following: What three parameters make up the epidemiological triangle?

Environmental factors, host factors, etiological agents

host range

he type of host (or cell within a host) they can infect

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

 Public education, quarantine, and vector control 

Define quarantine.

A period of confinement away from the general population for an animal or human that may have contracted an infectious disease; a measure intended to limit the spread of an infectious disease

How was the word Arbovirus derived? 

 Arthropod-borne viruses 

What is one major role of the Center for Disease Control (CDC)?

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

Define morbidity.

Presence of a disease in a population 

Define prevalence rate

 (or just prevalence) An epidemiological measure of frequency that describes morbidity in a given population during a specified time; to calculate the prevalence rate, take the total number of disease cases during a given time and divide it by the total number of people in the defined population during that same time

Define incidence rate.

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

Define mortality rate.

An epidemiological measure of association that indicates the 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. Also known as nosocomial infections

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

Contaminated medical devices and healthcare workers’ hands

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

 Clostridioides difficile gastrointestinal infections, urinary tract infections, surgical wound infections, methicillin-resistant Staphylococcus aureus bloodstream infections, intravascular device-related bloodstream infections, ventilator-associated events

Name five bacteria that are key HAI pathogens. 

Clostridioides difficile, E.coli, Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Vancomycin-resistant enterococci (VRE)

List five viruses that are key HAI pathogens.

Hepatitis B, Human Immunodeficiency virus (HIV), influenza, Viral gastroenteritis (mainly norovirus and rotavirus)

Name two fungi that are key HAI pathogens. 

Aspergillus mold species and candida yeast species

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

handwashing

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

Reportable: the diseases on a state or local tracking list, usually including the diseases that the CDC has an interest in monitoring, as well as diseases that the local authorities want to monitor.

Notifiable: diseases that the CDC recommends reporting to government health agencies for monitoring incidence; there are usually about 60 different infectious diseases (and a number of noninfectious diseases) on the CDC’s notifiable diseases list

Refresh your memory of emerging vs reemerging diseases that were covered earlier in this chapter.

Emerging: newer infectious diseases that exhibit an increasing incidence in populations.

Reemerging: diseases that were previously under control. But are now showing increased incidence; these include infections caused by well-known pathogens that have evolved increased virulence (capacity to cause disease)

Define disease eradication.

A term applied when there are no longer any causes of a particular disease anywhere in the world

What was the Tuskegee syphilis experiment?

Study to look at long term effects of syphilis in group of poor African American men. 

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 in children