Week 7 - Infection

Question 1

Define infection.

Answer 1

Pathogenic micro-organisms penetrate the host defenses, enter the tissues, and multiply

Question 2

Define infectious disease.

Answer 2

Pathologic state that occurs due to the disruption of a tissue or organ caused by microbes or their products

Question 3

Define pathogen.

Answer 3

A microbe whose relationship with its host is parasitic and results in infection and disease

Question 4

What is the type and severity of infectious disease dependent on?

Answer 4

Pathogenicity of the organism and condition of the host

Question 5

Define pathogenicity.

Answer 5

The ability of microbial species to produce disease (true and opportunistic pathogens)

Question 6

Define virulence.

Answer 6

The degree of damage caused by a microbe to its host

Question 7

Define true pathogen. Give an example.

Answer 7

Causes disease in a healthy person with normal immune defenses

Example: mycobacterium tuberculosis

Question 8

Define opportunistic pathogen.

Answer 8

Cause disease in immune compromised host and/or cause disease when access to sterile environment

Example: staphylococcus

Question 9

What are the 6 types of infections?

Answer 9

Primary infection

Reinfection

Superinfection

Secondary infection

Nosocomial infection

Subclinical infection

Question 10

Define the 6 types of infection.

Primary
Reinfection
Superinfection
Secondary infection
Nosocomial infection
Subclinical infection

Answer 10

Primary infection: initial infection with organism in host

Reinfection: subsequent infection by same organism in a host (after recovery)

Superinfection: infection by same organism in a host before recovery

Secondary infection: when in a host whose resistance is lowered by preexisting infectious disease, a new organism may set up in infection

Nosocomial infection: cross infection occurring in hospital

Subclinical infection: it is one where clinical affects are not apparent

Question 11

What are 7 details about infectious diseases throughout history?

Answer 11

Infectious agents have probably always caused disease in humans

Smallpox has been described in ancient Egyptian and Chinese writings and may have been responsible for more deaths than all other infectious diseases combined

There is evidence that malaria and poliomyelitis have existed since ancient times

In the 14th Century, the bubonic plague, or Black Death, killed about 20 million people in Europe alone

In the 20th Century, the 1918 influenza may have killed up to 50 million people worldwide

Close to 20 million people have died of AIDS to date

Potato blight (cause of the Irish Potato Famine)

Question 12

What are the 3 classifications of infectious disease?

Answer 12

Duration, location, and timing

Question 13

What kinds of diseases are classified by duration?

Answer 13

Acute: develops and runs its course quickly
Example: influenza

Chronic: develops more slowly and is usually less severe, but may persist for a long, indefinite period of time
Example: tuberculosis

Latent: characterized by periods of no symptoms between outbreaks of illness
Example: herpes

Question 14

What kinds of diseases are classified by location?

Answer 14

Local: confined to a specific area of the body

Systemic: a generalized illness that infects most of the body with pathogens distributed widely in tissues

Question 15

What kinds of diseases are classified by timing?

Answer 15

Primary: initial infection in a previously healthy person

Secondary: infection that occurs in a person weakened by a primary infection

Question 16

What are the 6 phases of infectious disease?

Answer 16

1. Exposure
2. Incubation period: time between infection and appearance of signs and symptoms
3. Prodromal period: mild, nonspecific symptoms that signal the onset of some diseases
4. Acute stage: person experiences typical signs and symptoms of disease
5. Recovery stage: symptoms have disappeared, tissues have healed, and body is slowly recovering strength
6. Convalescence: clinical symptoms have actually subsided

Question 17

What 6 elements are needed for the chain of infection?

Answer 17

1. Infectious agent
2. Reservoir
3. Portal of exit
4. Mode of transmission
5. Portal of entry
6. Susceptible host

Question 18

What are 3 details about portals of entry for infectious agents that enter the skin? Give examples of diseases that do this.

Answer 18

Nicks, abrasions, and punctures

Intact skin is very tough; few microbes can penetrate

Some create their own passageways using digestive enzymes

Examples:

Staphylococcus aureus
Streptococcus pyogenes
Haemophilus aegyptius
Chalmydia trachomatis
Neisseria gonorrhoeae

Question 19

What are 2 details about infectious diseases that use the gastrointestinal tract as a portal? Give examples of diseases that do this.

Answer 19

Pathogens contained in food, drink, and other ingested substances

Adapted to survive digestive enzymes and pH changes

Examples:

Salmonella
Shigella
Vibrio
Certain strains of Escherichia coli
Poliovirus
Hepatitis A virus
Echovirus
Rotavirus
Entamoeba hitolytica
Giardia lamblia

Question 20

What is 1 detail about infectious diseases that use the respiratory portal of entry? Give examples of diseases that use this.

Answer 20

The portal of entry for the greatest number of pathogens

Examples:
Streptococcal sore throat
Meningitis
Diphtheria
Whooping cough
Influenza
Measles
Mumps
Rubella
Chickenpox
Common cold
Bacteria and fungi causing pneumonia

Question 21

What are 3 details about diseases that use urogenital portals of entry? Gives examples of diseases that do this.

Answer 21

Sexually transmitted diseases (STDs)

Enter skin or mucosa of penis, external genitalia, vagina, cervix, and urethra

Some can penetrate an unbroken surface

Examples
Syphilis (treponema)
Gonorrhea (Nisseria)
Genital warts (Human papilloma virus)
Chlamydiosis (Chlamydia)

Question 22

What are 2 details about pathogens that infect during pregnancy and birth? Give examples of diseases that do this.

Answer 22

Some microbes can cross the placenta (ex. the syphilis spirochete, rubella)

Other infections occur prenatally when the child is contaminated by the birth canal

Examples:
Toxoplasmosis
Other diseases
Rubella
Cytomegalovirus
Herpes simplex

Question 23

What are 4 examples of exit portals?

Answer 23

Respiratory and salivary portals: coughing and sneezing, talking and laughing

Fecal Exit

Urogenital Tract

Removal of Blood or Bleeding

Question 24

What are the 5 methods of transmission of infection? Give examples of diseases for each transmission.

Answer 24

Contact (sexual intercourse):
syphilis, gonorrhea

Inhalation: influenza,
tuberculosis, smallpox, measles,
mumps, etc.

Ingestion: cholera (water), food
poisoning (food) and dysentery

Inoculation: tetanus (infection),
rabies (dog), serum hepatitis, i.e.
Hepatitis B (infection)

Congenital: syphilis, rubella, toxoplasmosis, cytomegaloviruses

Question 25

What is 1 detail about insects as a method of transmission?

Answer 25

Insects act as mechanical vector (dysentery and typhoid by housefly) or biological vector (malaria) of infectious disease

Question 26

Define reservoir.

Answer 26

The primary habitat in the natural world from which a pathogen originates

Question 27

Define a carrier. Give examples.

Answer 27

An individual who inconspicuously shelters a pathogen and spreads it to others without any notice Examples: Asymptomatic carriers: “Typhoid Mary” Incubation carriers Convalescent carriers

Question 28

Define a vector and give 2 details.

Answer 28

A live animal that transmits an infectious agent from one host to another Majority are arthropods Larger animals can also be vectors

Question 29

What 5 factors influence microbial growth?

Answer 29

Temperature pH, or the values used in chemistry to express the degrees of acidity or alkalinity of a substance Food Moisture Oxygen

Question 30

What are 4 categories of risk factors for infections that someone cannot typically control?

Answer 30

Heredity Aging Environmental conditions Organism virulence and resistance

Question 31

What are 7 risk factors someone can control?

Answer 31

Stress Nutrition Sleep Drug use Personal hygiene High-risk behaviors Exposure to products and services that increase risk

Question 32

Define emerging diseases.

Answer 32

Emerging diseases are those that have recently appeared within a population, or whose incidence or geographic range is increasing rapidly

Question 33

What 5 things affect disease emergence or re-emergence?

Answer 33

Appearance of a previously unknown agent Evolution of a new infectious agent Spread of an infectious agent to a new host Spread of an infectious agent to new locations Acquisition of resistance to anti-microbial drugs

Question 34

What 2 events must occur for a disease to become established?

Answer 34

1. The infectious agent must be introduced into a vulnerable population 2. The agent must have the ability to spread readily from person to person, cause disease, and sustain itself within the population

Question 35

What are 5 ways to reduce the spread of infectious diseases?

Answer 35

Vaccines Antimicrobial drugs Good personal hygiene and sanitation Protection against mosquitoes Quarantine

Question 36

What are 5 details about vaccines?

Answer 36

The most effective method of stemming the spread of infectious disease is through vaccination Vaccines consist of weakened or killed microbes, or just components of a pathogen, and stimulate the body’s natural defenses—the immune system—to combat infections Vaccination has eliminated smallpox, nearly eradicated poliovirus from much of the world, and drastically reduced the incidence of childhood infections, such as measles, mumps, and whooping cough, at least in the developed world Influenza vaccines are available to reduce the occurrence of seasonal flu, although the shot must be given yearly due to the extreme variance of the influenza virus from season to season Vaccines for other infectious diseases, especially HIV, still are being sought

Question 37

What are 4 details about antimicrobials?

Answer 37

Antibiotics are effective for many types of bacterial infections (although they are entirely useless against viruses) But increasingly, bacteria are becoming resistant to the arsenal of antibiotics at our disposal Very few drugs work well against viruses Anti-fungal drugs exist, but their use is limited

Question 38

What are 2 details about protection against mosquitos (and other insect vectors/parasites)?

Answer 38

There are no vaccines against protozoan parasites, and other medications against them are becoming ineffective Therefore, protection from insect vectors such as mosquitoes and control of mosquito populations are crucial strategies in containing the spread of insect-borne diseases, such as malaria

Question 39

What is 1 detail about sanitation?

Answer 39

Good sanitation, water purification, hand washing, and proper cooking and storage of foods all help to reduce the prevalence of infectious disease

Question 40

What are 2 details about quarantine?

Answer 40

In cases of highly contagious, often fatal diseases, quarantine is employed as a means of preventing the spread of disease through a community However, regardless of the disease, it is wise to limit contact with other individuals when ill

Question 41

What are the 3 overarching elements of the CDC's ID framework?

Answer 41

Element 1: strengthen public health fundamentals, including infectious disease surveillance, laboratory detection, and epidemiologic investigation Element 2: identify and implement high‐impact public health interventions to reduce infectious diseases Element 3: develop and advance policies to prevent, detect, and control infectious disease

Question 42

What are the 4 priorities for Element 1 of the CDC's ID framework? Element 1: strengthen public health fundamentals, including infectious disease surveillance, laboratory detection, and epidemiologic investigation

Answer 42

Modernize infectious disease surveillance to drive public health action Expand the role of public health and clinical laboratories in disease control and prevention Improve capacity for epidemiologic investigations and public health response Advance workforce development and training to sustain and strengthen public health practice

Question 43

What are the 2 priorities for Element 3 of the CDC's ID framework? Give examples of infectious disease issues of special concern. Element 3: develop and advance policies to prevent, detect, and control infectious disease

Answer 43

Identify and validate high‐impact tools for disease reduction Use proven tools and interventions to reduce high‐burden infectious diseases Examples: Antimicrobial resistance Chronic viral hepatitis Food safety Healthcare-associated infections HIV/AIDS Respiratory infections Safe water Vaccine-preventable diseases Zoonotic and vectorborne diseases

Question 44

What are the 2 priorities for Element 2 of the CDC's ID framework? Element 2: identify and implement high‐impact public health interventions to reduce infectious diseases

Answer 44

Ensure the availability of sound scientific data to support the development of evidence‐based and cost‐effective policies Activities that help make disease prevention a standardized, routine part of healthcare