PU520: Principles of Epidemiology Unit 2 Basic Infectious Disease Concepts

Question 1

What is an interruption, cessation, or disorder of body functions, systems, or organs?

Answer 1

Disease

Question 2

What is the primary focus of epidemiology?

Answer 2

Identifying the cause of disease and the mechanisms by which disease is spread.

Question 3

What is the science and study of the causes of disease and their mode of operation?

Answer 3

Etiology

Question 4

What are invading organisms that cause disease called?

Answer 4

Pathogens

Pathogens are defined as organisms or substances
such as bacteria, protozoa, viruses, fungi, abnormal or infectious prions (proteins produced by mutated genes), and parasites that are capable of producing disease.

Question 5

What is an infectious disease that is contagious, or capable of being communicated or transmitted?

Answer 5

Communicable disease

Question 6

What are some examples of infectious diseases that are not communicable?

Answer 6

Tetanus (found in the environment, and spores can remain in the soil, infectious, up to 40 years), Anthrax, legionnaires’ disease (inhaling bacteria in the environment), etc.

Question 7

Infectious communicable diseases may be transmitted through vertical and horizontal transmission. What is the difference between vertical and horizontal transmission?

Answer 7

Vertical transmission refers to transmission from an individual to its offspring through sperm, placenta, milk, or vaginal fluids.

Horizontal transmission of infectious agents from an infected individual to a susceptible contemporary.

Horizontal transmission may involve direct transmis-sion (e.g., sexually transmitted diseases), a common vehicle (e.g., waterborne, food-borne, or blood-borne
diseases), an airborne pathogen (e.g., tuberculosis), or a vector-borne pathogen (e.g., malaria).

Question 8

What refers to the capability of a dis-ease agent to enter, survive in, and multiply in a sus-ceptible host?

Answer 8

Infectivity

The host plays a major part in the ability of an organism to cause disease by providing nutrients and a life-sustaining environment.

Question 9

What is the disease-evoking power of a pathogen called?

Answer 9

Virulence

Essentially, the strength of the disease.

Question 10

What is a substance that works against pathogens due to its toxicity–that is, it contains elements that are more toxic to bacteria than the human body?

Answer 10

Antibiotics

Question 11

What is a poison and consequently kills pathogens by poisoning them?

An example of this is arsenic being used to treat syphilis.

Answer 11

Toxin

Question 11

What determines the level of toxicity of a substance?

Answer 11

The less of the substance needed and the speed of how fast it works, the higher the toxicity.

Question 12

Diseases are classified as acute and chronic. What does this mean?

Answer 12

Acute is a relatively severe disorder with sudden onset and short duration of symptoms.

Chronic is less severe but of continuous duration, lasting over long periods, it not a lifetime.

Question 12

What are the four stages of disease to run its course if not interventions are taken?

Answer 12

1. Stage of susceptibility
2. Stage of presymptomatic disease
3. Stage of clinical disease
4. Stage of recovery, disability, or death

Question 12

What stage of disease precedes the actual disease and involves the likelihood a host has of developing an ill effect from an external agent?

Answer 12

Stage 1

Question 13

What stage begins with exposure to or accumulation of factors sufficient to cause the disease process to begin and subsequent pathologic changes to occur in a susceptible host before signs of the disease appear?

Answer 13

Stage 2

For cancer, the exposure may be a factor that begins the process, such as a virus that disrupts signaling that normally keeps cell growth and proliferation in balance, or that weakens the immune system so the body is less capable of fighting off cancer-causing infections, or that results in chronic inflammation that leads to cancer.

Question 14

What is the time period between an infection by a pathogen and the first symptoms of disease?

Answer 14

The incubation period.

Question 15

What is the time when the disease is present but not symptomatic or detected?

Answer 15

Latency period. This may be used instead of incubation period for chronic diseases such as cancer.

Question 16

When does the stage of clinical disease begin?

Answer 16

At the onset of signs and symptoms.

Question 17

What stage reflects the expected prognosis?

Answer 17

The stage of recovery, disability, or death (stage 4)

Question 18

What are the five general categories that disease can be classified in?

Answer 18

Congenital and hereditary diseases
Allergies and inflammatory diseases
Degenerative diseases
Metabolic diseases
Cancer

Question 19

What category of disease are often caused by genetic and familial tendencies toward certain inborn abnormalities; injury to the embryo or fetus by environmental factors, chemicals, or agents such as drugs, alcohol, or smoking; or innate developmental problems possibly caused by chemicals or agents?

They can also be a fluke of nature.

Answer 19

Congenital and hereditary disease

Examples are Down syndrome, hemophilia, and heart disease present at birth.

Question 20

What category of disease are caused by the body reacting to an invasion of or injury by a foreign object or substance?

Answer 20

Allergies and inflammatory disease

Question 21

What is an allergen?

Answer 21

It is a substance that can cause an allergic reaction.

Animal proteins and animal dander, bacteria and viruses, chemicals, dust, drugs, foods, perfumes, plants, pollen, and smoke are common agents that can cause an inflammatory reaction in the body. Some inflammatory reactions may result in the body forming antibodies.

Question 22

What is formed within the body as a first line of defense and are protein substances or globulins derived from B and T lymphocytes that originate in the bone marrow?

Answer 22

Antibodies

Question 22

What category of disease cause a lower level of mental, physical, or moral state than is normal or acceptable?

Answer 22

Degenerative disease

These are often associated with the aging process but in some cases may not be age related.

Arteriosclerosis, arthritis, and gout are examples of degenerative chronic diseases.

Question 23

What category of diseases cause the dysfunction, poor function, or malfunction of certain organs or physiologic processes in the body, leading to disease states?

Answer 23

Metabolic disease

Glands or organs that fail to secrete certain biochemicals to keep the metabolic process functioning in the body cause metabolic disorders.

For example, adrenal glands may stop functioning properly, causing Addison’s disease; the cells may no longer use glucose normally, causing diabetes; or the thyroid gland might fail, resulting in a goiter, hyperthyroidism, or cretin-ism (hypothyroidism).

Question 24

What are some portals of entry into the human body?

Answer 24

Respiratory, oral, reproductive, intravenous, urinary, skin, mucous membrane, open wounds, gastrointestinal, conjunctival (eye), transplacental, and tubes inserted in the body like a catheter.

Question 24

What category of disease that is a collective name that refers to a group of many diseases with one common characteristic: uncontrolled cell growth or the loss of the cell’s ability to perform apoptosis (cell suicide)?

Answer 24

Cancer

The gradual increase in the number of uncontrolled dividing cells creates a mass of tissue called a tumor (neoplasm). When a tumor is malignant, meaning that it is capable of spreading to surrounding tissue or remote places in the body, it is called cancer.

Question 24

What are the five different means of transmission that is used to classify certain infectious diseases?

Answer 24

1. Airborne or respiratory transmission
2. Transmission through intestinal (alvine) discharge (this includes waterborne and foodborne diseases)
3. Transmission through open lesions
4. Zoonotic or vector-borne transmission
   5 Fomite-borne transmission

Question 24

What are some microbe organisms that cause disease?

Answer 24

Bacilli (cholera), Cocci (Gonorrhea), Spiral organisms (syphilis), acid-fast organisms (TB)

Rickettsia (very small bacteria; Typhus)

Viruses (HIV, HPV, Rabies, Chickenpox, Influenza, etc)

Fungi (Mycosis)
Molds (Ringworm)
Yeast (blastomycosis)

Question 25

T/F Diseases with shorter incubation periods are typically produce a more acute and severe illness, whereas long incubation diseases are less severe, although there are, of course, exceptions.

Answer 25

True

Question 25

What is the prodromal period?

Answer 25

It is the second stage of disease (the stage where signs and symptoms first appear)

Many diseases at this stage makes diagnosis difficult since many diseases produce the same symptoms.

Question 25

What are some animal sourced diseases?

Answer 25

Protozoa (dysentery, malaria)

Worms (ascaris)
- Trichinellae (Trichinosis)

Arthropods (Scabies)

Question 26

What would you expect during the defervescence period of the disease?

Answer 26

Symptoms of the illness begin to decline, and the patient may feel that they are recovering, even though they still cannot take care of themselves.

If the immune system is weakened and cannot effectively fight off the pathogens, a relapse may occur at this stage. This is also a period when the likelihood of transmission of the disease is quite high because patients may be up and about, although not yet recovered and still infectious.

Question 26

What is the period when the disease is at its maximum severity or intensity?

Answer 26

Fastigium.

Diagnosis is the easiest at this point. In the fastigium stage, even though the disease is highly communicable, patients do not spread it much. Usually in this phase of the disease, the sick person is home in bed or in the hospital.

Question 27

What is the convalescence period of the disease?

Answer 27

Recovery. Those affected may still be infectious at this point but are feeling much better. They may be out and about, spreading the disease.

Question 28

What is the period of disease during which the pathogen is killed off or brought into remission by the immune system?

Answer 28

Defection

In some diseases, defection and convalescence may be the same stage. If isolation is required, it is in the defection stage that isolation is lifted.

Question 29

Why is it important to always consider the virulence and viability of a disease?

Answer 29

High virulence can cause more severe cases and death, while viability is the capacity of the pathogen to survive outside the host and to exist or thrive in the environment.

Question 30

Why would a disease be considered subclinical?

Answer 30

When it has yet manifested itself or produces only mild symptoms, it is referred as subclinical.

The presence of some diseases can be revealed with clinical tests such as blood analysis; however, clinical symptoms may not be apparent. This state is also referred to as a subclinical infection or subclinical case. In the absence of clinical symptoms, such a condition must be confirmed immunologically.

Question 31

What are some examples of inanimate sources of illness an disability?

Answer 31

Dusts (asbestos), fumes (lead), smoke, gases, electrical energy, noise, ionizing radiation, nonionizing radiation, thermal energy, ergonomic problems, stress, bites, stings, chemical ingestion.

Question 32

What is an infectious organism in vertebrate animals (ebola, salmonella, rabies, anthrax, etc.) that can be transmitted to humans through direct contact, a fomite, or vector?

Answer 32

Zoonosis (zoon = animal and noses = ill)

Question 33

What are some potential carriers of infectious organisms that can be zoonotic?

Answer 33

Assassin bugs, bank voles, bats, birds, cats, cattle, chimpanzees, dogs, fish, fleas, flies, geese, goats, hamsters, horses, humans, lice, mice, monkeys, mosquitos, pigs, possums, rabbits, raccoons, rats, rodents, sheep, sloths, snails, and ticks.

Question 34

Fun Fact: Coyotes can carry plague, never becoming sick from the disease, yet spreading it to rodents and humans via a flea vector. Humans may get bitten by a flea while in the woods or at home, get ill a few days later, and not connect their disease to the inoculation by the insect. Historically, the animal–flea–human set of events was a connection not easily made. For hundreds of years, humans got malaria from mosquito bites and never realized that the disease came from the mosquito. The same was also true for the sequence of events from flea bites to plague.

Answer 34

N/A

Question 35

Who provides internationally endorsed standard diagnostic classifications for general epidemiologic and health management purposes?

Answer 35

The World Health Organization (WHO).

In 1990, the 43rd World Health Assembly endorsed International Classification of Diseases 10 (ICD-10). In 1994, it came into use by WHO member states.

The ICD uses death certificates, hospital records, and other sources to classify diseases and health-related problems. The classifications provide a basis for comparing morbidity and mortality statistics among WHO member states. The ICD facilitates the analysis of the general health and well-being of populations. The monitoring of incidence, prevalence, mortality data, and health-related problems is made possible because of standard diagnostic classifications.

Question 36

Who has taken charge of collecting and publishing data on nationally notifiable diseases which changes from year to year to reflect the emergence of new pathogens or the decline in incidence of certain diseases?

Answer 36

The Centers for Disease Control and Prevention.

It is no longer law for states to report nationally notifiable diseases to the CDC, but voluntary.

State regulations specify the diseases that must be reported, who is responsible for reporting, the information required on each case, to whom and how quickly the information is to be reported, and the expected control measures to be taken for specific diseases.

This varies state by state.

State health departments also expect reporting of diseases experiencing unusually high incidence and the occurrence of any unusual disease that has public health importance.

Question 37

Who is required to report of notifiable diseases within a state?

Answer 37

Reporting of notifiable diseases is required of physicians, dentists, nurses, other health practitioners, and medical examiners. It may also be required or requested of laboratory directors and administrators of hospitals, clinics, nursing homes, schools, and nurseries.

Question 38

What is the timeframe for notification of notifiable diseases?

Answer 38

Individual reports are treated as confidential, and the required timing of reporting the disease may be immediately done by telephone, within 1 day of identification, or within 7 days of identification.

For example, anthrax is expected to be reported immediately, whereas AIDS should be reported within a week of identification.

Case reports are typically sent to local health departments. The local health department then communicates the information to the state. Where local health departments do not exist or are not in a position to respond to the health problem, or where the state health department has elected to take primary responsibility, case reports are sent directly to the state health department.

Question 39

What are the two classifications of disease immunity?

Answer 39

Active and Passive

Question 39

What is the introduction of a substance that can cause the immune system to respond and develop antibodies against a disease?

Answer 39

Immunization

The immunization of 60 million children from 1963 to 1972 cost $180 million but saved $1.3 billion by averting 24 million cases of measles. In the end, 2,400 lives were saved, 7,900 cases of retardation were prevented, and 1,352,000 hospital days were saved.

Question 40

What classification of immunity involves the transfer of antibodies to one person produced by another person?

Answer 40

Passive immunity

Passive immunity may be acquired through transplacental transfer or breastfeeding. Passive immunity can also come from the introduction of already-produced antibodies by another host (e.g., immune globulin).

Passive immunity is comparatively short lived, usually lasting a few weeks or months.

Question 40

What is based on the notion that if the herd (a population or group) is mostly protected from a disease by immunity, the chance that a major epidemic will occur is limited?

Answer 40

Herd immunity

The term “herd immunity” was first introduced in 1923. Jonas Salk (1914–1995), one of the developers of the polio vaccine, suggested that if a herd immunity level of 85% exists in a population, a polio epidemic will not occur. Herd immunity is also viewed as the resistance a population has to the invasion and spread of an infectious disease.

Question 41

What classification of immunity does the body produce its own antibodies against a specific invading substance, called an antigen thereby providing very selective protection?

Answer 41

Active immunity

This can occur through a vaccine or in response to having a specific disease pathogen invade the body. Active immunity is usually permanent, lasting throughout one’s lifetime.

Question 42

What do you call the ability of the antigen system to have the strength, activity, and effectiveness to respond to disease?

Answer 42

Antigenicity

The antigens stimulate the immune system to make the body think it has the disease. The body’s immune system responds by developing antibodies and a natural immunity to the disease.

If the pathogen later enters the body, the immune system recognizes it, and the body is protected from the disease by the rapid response of the immune system. Some vaccines last a lifetime; others may not.

Recent reports indicate that revaccination may be required for some diseases as one gets older. Booster shots keep the immune process active within the body. If antigens and antibodies disappear over time, a booster shot is needed to strengthen or reactivate the immune response. Booster shots are also given at the outset of an immunization program to help build the body’s immune defense systems to the fullest extent possible.

Question 43

What are the three key factors to the control of communicable diseases?

The methods of prevention and control are used on several fronts; What are the three fronts?

Answer 43

• Remove, eliminate, or contain the cause or source of infection
• Disrupt and block the chain of disease transmission
• Protect the susceptible population against infection and disease

-Environment
-Person at risk (host)
-Population or community

Question 44

For prevention and control, what is the aim of the environmental front?

Answer 44

• Providing clean and safe air, water, milk, and food.
• Management of solid waste, liquid waste, and control of vectors.

Question 45

For prevention and control, what is the aim of the host-related front?

Answer 45

Protection measures include isolation, quarantine, sanitation, good hygiene, immunizations, and chemoprophylaxis.

Control can be attributable to quarantine and isolation.

Question 46

What is the difference between quarantine and isolation?

Answer 46

Quarantine applies to persons who have been exposed to a contagious dis-ease but may or may not become ill. These people may not know whether they have been exposed to a disease, or they may have the disease but not manifest clinical symptoms (e.g., Typhoid Mary).

Isolation applies to persons who are known to be ill with a contagious disease. It is often conducted on an inpatient basis in hospitals or nursing homes. Most state laws and accrediting organizations require one or two beds to be kept, designated, and equipped in a hospital or nursing home as isolation beds.

Question 46

What is a consequence of consuming too few essential vitamins, minerals, and other nutrients or excreting them faster than they can be replenished. Inadequate intake may result from excessive dieting, severe injury, and serious illness? Excessive loss may result from diarrhea, heavy sweating, heavy bleeding, or kidney failure.

Answer 46

Undernutrition

Question 46

What is a form of malnutrition in which there is an excessive intake of nutrients?

Answer 46

Overnutrition

Question 47

What does malnutrition mean?

Answer 47

Refers to a condition that arises when the body does not get the right amount of vitamins, minerals, and other nutrients to maintain healthy tissues
and proper organ function.

Question 48

What is the diminished capacity to perform within a prescribed range?

Answer 48

Disability

Question 49

What is any loss or abnormality of psycho-logical, physiologic, or anatomic structure or function?

Answer 49

Impairment

Impairment is often associated with or results from chronic disease because it represents a decrease in or loss of ability to perform various functions, particularly those of the musculoskeletal system and the sense organs. Impairment may also result from a condition, injury, or congenital malformation.

Question 50

What involves difficulty an individual may have in executing activities?

Answer 50

Activity limitation

Question 51

What is any problem individuals may experience in their involvement in life situations?

Answer 51

Participation restriction

Question 52

What is Ro? (R-nought)?

Reducing spread can be done by:

• Blocking transmission (isolation, ppe)

Vaccines (Measles –> MMR)

Answer 52

It is the number of new cases that an existing case generates on average over the infectious period in a susceptible population.

Ro = new cases/existing cases infectious period (days => years)

The infectious period passes for a defined amount of time… You then divide the new cases over the existing ones to determine the Ro.

Ro < 1 will typically die out.

Ro = 1 will typically remain stable

Ro > 1 will typically spread