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Intro to Public Health > Module 7 (Biological Basis of Infectious Disease) > Flashcards

Module 7 (Biological Basis of Infectious Disease) Flashcards

1
Q

What were major factors that led to the decline of infectious disease mortality?

A

40 states had health departments by 1900

First municipal use of chlorine in water in US (circa 1910)

First use of Penicillin (circa 1940)

Salk Vaccine Introduced (circa 1950)

Passage of Vaccination Assistance Act (1962)

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2
Q

What is the Vaccination Assistance Act (1962)?

A

The Vaccination Assistance Act, signed in 1962 by President John F. Kennedy, made available funds to ensure all children under the age of five could receive vaccines, regardless of family economic status.

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3
Q

What are pathogens?

A

In biology, a pathogen, in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.

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4
Q

What are examples of bacterial illnesses?

A

tuberculosis
cholera
typhoid
tetanus
diphtheria
dysentery
syphilis
streptococci
staphylococci
salmonella

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5
Q

What are examples of viral illnesses?

A

smallpox
poliomyelitis
hepatitis
measles
rabies
AIDS
yellow fever

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6
Q

What are examples of parasitic illnesses?

A

malaria
cryptosporidiosis
giardiasis (diarrhea & intestinal)
roundworms
tapeworms
hookworms
pinworms
dracunculiasis

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7
Q

What are examples of fungal illnesses?

A

Candidiasis (yeast infections)
Cryptococcosis
Aspergillosis
Valley Fever
Histoplasmosis
Blastomycosis
Pneumocystis Pneumonia

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8
Q

What are Koch’s postulates?

A
  1. Suspected causative agent must be absent from all healthy organisms but present in diseased organisms
  2. Causative agent must be isolated from the disease organism and grown in pure culture
  3. Cultured agent must cause the same disease when inoculated into a healthy, susceptible organism
  4. Same causative agent must then be reisolated from the inoculated, diseased organism
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9
Q

What are example modes of disease transmission?

A

droplet
direct contact
vector
vehicle
airborne

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10
Q

What are human / animal host defenses against infection?

A

natural barriers
nonspecific immune mechanisms
specific immune responses

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11
Q

What are the human body’s specific immunity mechanisms?

A

Lymph nodes – recognize and eliminate invading pathogens

White blood cells– attack pathogens both in blood and in other body tissues

Spleen – assist body in protecting itself from bacterial infection

Stomach–stomach kills most harmful bacteria

Intestines– secrete antibodies which attack pathogens in the intestinal tract

Respiratory System – the cilia line the airway and move mucus & contaminants upward and out of the respiratory tract

Skin– effective barrier against invading pathogens

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12
Q

What are the human body’s nonspecific immune mechanisms?

A

Essentially, taking a microbe / external particle and combining it with a lysosome, digesting it until it becomes a “residual body,” then releasing it via elimination organs (discharge of waste material)

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13
Q

What are the human body’s three best defenses against infection?

A

antibodies (blood proteins made to fight specific antigens) and lymphocytes (a type of white blood cell, including B and T cells) and macrophages (another type of white blood cell).

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14
Q

What is an antigen?

A

a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.

(can be the same as a pathogen…?)

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15
Q

What are T cells?

A

are a diverse and important group of lymphocytes that mature and undergo a positive and negative selection processes in the thymus. The directly fight antigens and infections.

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16
Q

What are memory T cells?

A

Memory T cells are a class of T cells that persist after having previously responded to antigenic stimulation, for example, prior infection. Upon re-exposure to antigen, memory T cells mount a more vigorous response than in the initial exposure.

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17
Q

What are macrophages?

A

Macrophages are effector cells of the innate immune system that phagocytose bacteria and secrete both pro-inflammatory and antimicrobial mediators. In addition, macrophages play an important role in eliminating diseased and damaged cells through their programmed cell death.

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18
Q

What do B cells do?

A

Generally, B-cell is a key regulatory cell in the immune system; it acts by producing antibodies, antigen-presenting cells, supporting other mononuclear cells, and contributing to inflammatory pathways directly

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19
Q

What is the difference between B cells and T cells?

A

While B-cells produce antibodies to fight infection, T-cells protect people from getting infected by destroying cancerous and infected cells.

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20
Q

What are current issues with antibiotic use?

A

over-prescription (around 30% of prescriptions are unnecessary, and even the appropriate ones need adjusting)

microbial resistance

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21
Q

What are the different types of vaccines?

A

live, attenuated (weakened) virus
inactivated (killed germ) virus
toxoid (harmful product made by germ)
subunit (fragment of protein or polysaccharide from pathogen)
conjugate (combines weak antigen with strong antigen to inspire immune response)

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22
Q

What do vaccines do?

A

Vaccines can train your body to prevent sicknesses before they even start. They do this by introducing something called an antigen into the body, which imitates an infection and primes the immune system to respond.

They teach the immune system to memorize the response to a pathogen

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23
Q

What is herd immunity?

A

resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination.

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24
Q

Describe the fecal / oral route of infection

A
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25
Q

Describe the general transmission of infection pathway

A
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26
Q

What are environmental factors that affect immunity?

A

Water
Wastes
Food
Air
Inanimate Objects

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27
Q

What are some examples of how human development increases the risk of contagion spread and outbreaks?

A

development of agriculture
urbanization
globalization
rapid means of travel

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28
Q

What is the significance of HIV in disease transmission?

A

It weakens the immune system by destroying t cells

Still no effective cure, just therapy & reducing effects

Multiple means of transmission (blood, semen, rectal fluid, vaginal fluid, breast milk)

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29
Q

What is the significance of smallpox in disease transmission?

A

It is the only disease to have been fully eradicated
(had about 30% mortality rate)

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30
Q

What is the significance of Influenza in disease transmission?

A

Spreads by droplets of fluids through the air

Undergoes rapid mutation and re-assortment of characteristics, allowing it to continually evade the immune system

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31
Q

What are the 4 types of flu virus?

A

Category is determined via antigen type

Influenza A - the only type known to cause flu epidemics. Divided into two types based on the proteins used. Most come from wild birds. Reassortment of gene segments is highly common. Example: Swine Flu (H1N1)

Influenza B - Divide into 2 lineages. Tend to change more slowly than type A, so less dangerous overall. Considered a part of seasonal epidemics (along with A).

Influenza C - causes cold like symptoms (usually in young children), more mild. Not considered a part of seasonal epidemics.

Influenza D- affect cattle with spillover to other animals but not humans

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32
Q

What are the Bradford Hill Criteria for Causation?

A

The Bradford Hill criteria include nine viewpoints by which to evaluate human epidemiologic evidence to determine if causation can be deduced: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, and analogy.

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33
Q

When did infectious disease stop being the major killer of humans?

A

Around the start of the 20th century

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34
Q

How much of Europe and Asia did the Bubonic Plague / Black death kill?

A

75% of the population in the 14th century

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35
Q

What was the number one killer in England in the 19th century?

A

Tuberculosis

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36
Q

How were infectious diseases reduced?

A

Public health methods, including purification of water, disposal of sewage, pasteurization of milk, immunization, and improved nutrition / personal hygiene.

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37
Q

When were antibiotics discovered?

A

The 1940s

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38
Q

What are most major epidemic diseases caused by?

A

bacteria, viruses, parasites

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39
Q

When were the specific microbes (bacteria, virus, parasite) discovered?

A

The 1880s and 1890s

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40
Q

What did WM Stanley do in 1935?

A

Crystallized tobacco mosaic virus, demonstrating the true nature of viruses (filterable and tiny)

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41
Q

What is the difference between bacteria and virus?

A

Bacteria are single celled organisms that can exist outside the body if given appropriate nutrients

Viruses are not complete cells. Complexes of nucleic acid and proteins cannot reproduce by themselves. They infect human, animal, and plant cells - or even bacteria. They can survive harsh conditions

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42
Q

What are protozoa?

A

Single celled animals that can live as parasites in the human body (e.g. malaria, giardiasis)

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43
Q

What are the most common causes of human infection around the world?

A

Parasites, including roundworms, hookworms, tapeworms, and pinworms. Only pinworms are found much in the US.

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44
Q

What are aerosols in terms of disease transmission?

A

Water droplets produced when an infected person coughs or sneezes (transmitter of respiratory viruses / bacterium)

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45
Q

How are gastrointestinal infections usually spread?

A

The fecal oral route

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46
Q

How do we control infectious diseases?

A

By interrupting the Chain of Infection

47
Q

How was the SARs virus eliminated?

A

Not via a “cure,” per se, but the old fashioned way - quarantine and limited exposure

48
Q

What situation brought on the concept of vaccination?

A

Smallpox epidemic

49
Q

Why is the proposed destruction of smallpox controversial?

A

Only two labs have it - CDC and a Russian lab. Some believe the Russians were preparing to keep it and use it as a bioweapon. The anthrax attacks of 2001 raised more concern. Some scientists also believe there is more to be learned about smallpox. A decision has not yet been made.

50
Q

What countries still have endemic polio?

A

Afghanistan and Pakistan

51
Q

Why is polio harder to end than smallpox?

A

It has many carrier cases, sometimes the vaccination needs to be administered several times in order to fully work, and political upheaval especially in remote areas, e.g. in Pakistan and Nigeria polio vaccinators have been killed by Islamic extremists

52
Q

Why did Malaria experience heavy resurgence?

A

The campaign using pesticide DDT ran out of funding before all mosquitoes could be killed. New mosquitoes with DDT resistance were developed.

53
Q

How many people does malaria kill annually?

A

1 million, mainly children

54
Q

Who does herd immunity especially help protect?

A

Those who cannot be vaccinated, including young babies and people with weakened immune systems

55
Q

What are 3 historically prevalent diseases with no nonhuman reservoir?

A

smallpox, measles, polio

56
Q

How is rabies controlled in the US?

A

primarily through the vaccination of dogs

57
Q

What was the story of smallpox blankets?

A

1763-1764, Biological Warfare

The British give smallpox-contaminated blankets to Shawnee and Lenape (Delaware) communities—an action sanctioned by the British officers Sir Jeffery Amherst and his replacement, General Thomas Gage.

58
Q

Who was typhoid Mary?

A

Mary Mallon, known commonly as Typhoid Mary, was an Irish-born American cook believed to have infected between 51 and 122 people with typhoid fever. The infections caused three confirmed deaths, with unconfirmed estimates of as many as 50.

Mary was an asymptomatic carrier and refused to get tested, then refused to believe her test results due to her health and cooking being her only means of making a living. She was incarcerated for the rest of her life after refusing to stop cooking

59
Q

What is contact tracing?

A

Contact tracing is the process of identifying people who have
recently been in contact with someone diagnosed with an
infectious disease. Once a person tests positive for a disease, they will be asked to list the people they have been in contact with and the places they visited during the period in which they were contagious. The patient’s contacts will be notified by the health department or by contact tracers who will explain what precautions they need to take and for how long. This may include a quarantine period during which the person should avoid contact with others. During the disease’s incubation period, contact tracers will continue to check on the close contacts to see if they have developed symptoms or tested positive for the disease.

60
Q

What did Edward Jenner do for smallpox?

A

The basis for vaccination began in 1796 when the English doctor Edward Jenner noticed that milkmaids who had gotten cowpox were protected from smallpox. Jenner also knew about variolation and guessed that exposure to cowpox could be used to protect against smallpox.

61
Q

What were the 2001 anthrax attacks?

A

In 2001, powdered anthrax spores were deliberately put into letters that were mailed through the U.S. postal system. Twenty-two people, including 12 mail handlers, got anthrax, and five of these 22 people died.

Suspected instigator was US Army scientists Bruce Ivins (not proved)

62
Q

What disease changed the opinion that infectious diseases were mostly under control?

A

Human Immunodeficiency Virus

63
Q

What is a retrovirus?

A

A virus that uses RNA as genetic material rather than DNA

64
Q

At what point does HIV develop fully into AIDS (Acquired Immunodeficiency Syndrome)?

A

When T4 cell levels drop below 200 per cubic milliliter of blood (20% the normal level) and the body becomes susceptible to many infections & tumors (and highly transmittable to others)

65
Q

What is viral load?

A

Concentration of a virus in the blood

66
Q

How is measuring viral load helpful?

A

Evaluates the effectiveness of therapeutic drugs for viruses such as HIV

Reducing viral load reduces the chance of transmitting infection

67
Q

How have HIV tests changed?

A

They initially tested for antibodies, which often missed then 3 to 6 week “latent” period

Now they use blood tests, which confirmed viral presence after screening - this is also used for all donated blood

68
Q

What is Highly Active Antiretroviral Therapy (HAART)?

A

a medication regimen used to manage and treat human immunodeficiency virus type 1 (HIV-1). It is composed of several drugs in the antiretroviral classes of medications.

Some of these use protease inhibitors, which interfere with the ability of newly formed viruses to mature and become infectious (introduced in 1995)

Greatly reduces viral load

69
Q

What is the controversy of using HAART?

A

Side effects can be severe and even fatal

70
Q

What are other drugs being studies on treatment of HIV?

A

Fusion inhibitors - interferes with HIVs ability to enter a host cell

Integrase inhibitors: prevent virus from being integrated into genetic material of human cells

71
Q

What are current issues with HIV treatment?

A

There is no cure, only maintenance

Drugs are expensive and often not fully covered by insurance

72
Q

What is a common characteristic of RNA viruses in relation to vaccines?

A

They can mutate and adapt quickly, making it difficult to form effective vaccinations for them

73
Q

How many died from the initial spread of Ebola in Zaire and Sudan?

A

As many as 90%

74
Q

Who does Ebola affect?

A

Humans, monkeys, and apes

Fruit bats are thought to be reservoirs between infections

75
Q

When did the major African Ebola epidemic start?

A

2014 (hardest hit were Liberia, Guinea, and Sierra Leone)

Often spread by tradition of kissing the dead (ebola rampant on corpses)

Virus stays present even after symptoms abate – male survivors advised to wear condoms for an undetermined period

76
Q

What disease led to concerns about exotic pets?

A

Monkeypox, which is primarily hosted by rodents (and can infect monkeys).

77
Q

What are some lesser known, emerging viruses?

A

Hantavirus Pulmonary Syndrome
Hemorrhagic Fevers (hosted by various rodents)
Yellow Fever
Equine Encephalitis

78
Q

What is especially dangerous about Dengue Fever?

A

It is caused by 4 different viruses transmitted via mosquitoes, meaning a survivor can still be infected 3 more times

79
Q

How did West Nile virus likely enter America?

A

Through a smuggled exotic bird

80
Q

How many people did West Nile infect in 2018?

A

2647 people, making it the most common mosquito born disease in the US

81
Q

When was Zika Virus first identified?

A

1947 among monkeys of Zika Forest in Uganda

82
Q

When did Zika come to worldwide attention?

A

in 2015, when a Brazilian outbreak infected over 1 million people

83
Q

What is the most severe affect of Zika virus?

A

Unborn fetuses, who often die or develop microcephaly & severe neurological damage

84
Q

What was a failing in addressing the Zika virus?

A

Informing poor Brazilian pregnant women, causing a surge of damaged infants

85
Q

How many people does influenza affect every year?

A

8% of US population gets it, and 40k Americans die (usually over age 65)

86
Q

How many were affected by the Spanish flu pandemic of 1918-1919

A

20 to 40 million died, including almost 200k in the US

Disproportionately affected young people

87
Q

Historically, what are the most lethal strains of the flu?

A

Spanish flu (1918)
Asian flu (1957)
Hong Kong Flu (1968)
Swine Flu? (false alarm)
Avian Flu (2003)
Avian Flu - to birds only (2015)

88
Q

Why is Asia such a carrier for flu viruses?

A

Reservoirs of flu (pigs and birds) are common in Asia and live in close proximity to humans

Pigs develop viruses in their digestive systems, then birds pick them up and migrate

89
Q

What are some concerning bacterial threats?

A

Legionnaire’s disease
Lyme disease
Salmonella
Campylobacter
MRSA (Methicillin-resistant Staphylococcus aureus)
(extensively) multi drug resistant Tuberculosis

Antibiotic Resistance

90
Q

How does antibiotic resistance work?

A

Any mutation of bacteria that allows a single bacterium to survive confers selective advantage - it can reproduce without threat from other microbes. This mutated gene can also spread to other kinds of bacteria through plasmids (small pieces of DNA that move between bacterium)

Caused often by prescribing antibiotics for viral infections and by patients ending their antibiotic treatment when they fell better (not finishing the dose)

91
Q

What is Directly Observed Therapy?

A

DOT means that a trained health care worker or other designated individual (excluding a family member) provides the prescribed TB drugs and watches the patient swallow every dose.

92
Q

When were prions discovered?

A

With the emergence of Creutzfeldt-Jakob Disease in the 1990s

93
Q

What are prions?

A

A prion is a misfolded protein that can transmit its misfoldedness to normal variants of the same protein and trigger cellular death. Prions cause prion diseases known as transmissible spongiform encephalopathies that are transmissible, fatal neurodegenerative diseases in humans and animals.

94
Q

What are crowd epidemic diseases?

A

diseases caused by pathogens which rely on large numbers of people to host and spread them

94
Q

How many emerging infectious diseases come from animals to humans?

A

2/3, including rabies, Zika, West Nile, lyme, anthrax, ebola, AIDs, and bubonic plague

95
Q

How were wet markets a part of the Covid 19 pandemic?

A

these are breeding grounds for animal viruses due to crowded and unsanitary conditions, and mixing of different animals

Wuhan also had a market of “exotic” animals by western standards, including bats, pangolins, and monkeys

96
Q

What is gain of function research?

A

medical research that genetically alters an organism in a way that may enhance the biological functions of gene products. This may include an altered pathogenesis, transmissibility, or host range, i.e., the types of hosts that a microorganism can infect.

e.g. mutating a virus so it can go from infecting animals to humans

97
Q

What gain of function research was Wuhan Institute of Virology conducting?

A

coronaviruses in bats; using potentially pandemic pathogens for research - but one likely escaped

98
Q

What are other cases of studied viruses escaping from infectious disease labs?

A

1977 influenza
1963-1978 smallpox
6 escapes of SARs in Asia (thankfully quickly contained)

99
Q

How many Covid 19 deaths in the US were among nursing home clients?

A

About 1/3

100
Q

What is fomite mediated transmission?

A

A fomite refers to inanimate objects that can carry and spread disease and infectious agents. Fomites can also be called passive vectors.

101
Q

What is a basic reproduction number?

A

denoted Re or Rt, is the expected number of new infections caused by an infectious individual in a population.

Becomes “effective reproduction number” when some members of the population may no longer be susceptible

102
Q

What was the super spread situation for Covid 19?

A

10% of cases caused 80% of spread

103
Q

What is the difference between mitigation and suppression?

A

Mitigation aims to limit the disease’s damage by keeping hospitals below capacity

Suppressions aims to eliminate virus altogether

104
Q

What are the 3 purposes of Testing Programs?

A
  1. Testing for personal use
  2. Testing for surveillance
  3. Testing for mitigation
105
Q

How did Covid 19 economically impact the US?

A

it caused the largest drops in employment and consumer spending ever recorded

global economic collapse unlike anything seen since the Great Depression in the 1930s

106
Q

What populations were hit hardest by Covid?

A

Elderly, Black, and Hispanic

107
Q

How did Covid affect different countries?

A
108
Q

What is the SIR formula?

A
109
Q

Describe the trend of Measles infections

A
110
Q

Describe the chain of infections

A
111
Q

________ is an example of a human disease caused by a protozoan.

A

Malaria

112
Q

What is the most common route of transmission of the HIV virus in developing countries?

A

In most developing countries, heterosexual transmission is the dominant mode of spread, and mother to child transmission of HIV is much more common than in industrialized countries.

Homosexual transmission is more common in developed countries

Intro to Public Health (14 decks)

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