Module 7: Causes of Infectious Disease Flashcards
Inquiry question: How are diseases transmitted? (142 cards)
1
Q
What are the 4 modes of disease transmission?
A
Direct contact, indirect contact, vector transmission, and vehicle transmission.
2
Q
What does direct contact involve?
A
This involves the individuals physically transferring the pathogens.
3
Q
What does indirect contact involve?
A
This involves objects being contaminated with pathogens. These contaminated objects are known as fomites.
4
Q
What are fomites?
A
Objects contaminated with pathogens, that aid the spread of disease via indirect contact.
5
Q
How are droplets related to disease transmission?
A
Many infectious diseases can be spread via droplets, which form from the moisture in breath. Coughing, sneezing, and exhaling can spread these droplets to others and the environment.
6
Q
What is the spread of a pathogen from an infected individual to another susceptible individual?
A
Transmission.
7
Q
What is transmission?
A
The spread of a pathogen from an infected individual to another susceptible individual.
8
Q
What does vehicle transmission involve?
A
The spread of pathogens by contaminated air, food, or water.
9
Q
What does vector transmission involve?
A
Animals assisting in the transfer of pathogens between individuals.
10
Q
What are the two types of vectors?
A
Biological vectors and mechanical vectors.
11
Q
What are biological vectors?
A
They transfer the pathogen from one individual to another, but the pathogen also undergoes part of its life cycle in the vector.
12
Q
What are mechanical vectors?
A
They physically transfer the pathogen from one person to another without being infected themselves.
13
Q
What are 3 examples of how disease can be spread by direct contact?
A
Touching, kissing, and sexual intercourse.
14
Q
What are 4 examples of how disease can be spread by indirect contact?
A
Used bedsheets, contaminated medical equipment, a used tissue, and saliva traces on a fork.
15
Q
What is an example of a biological vector, and what role does it play in disease transmission?
A
Mosquitoes become infected when they bite an infected animal or human, acquiring the pathogen. The pathogen multiplies within the mosquito’s body, and when the mosquito bites another organism, the pathogen is passed on. This is evident in diseases such as malaria and dengue fever.
16
Q
What is an example of a mechanical vector, and what role does it play in disease transmission?
A
Flies can pick up pathogens on their feet, bodies, or mouthparts from sources like feces, garbage, or infected animals, and then deposit them on food, people, or other surfaces. They can be vectors in diseases such as typhoid fever, salmonella, and cholera.
17
Q
What are the 2 ways water purification works?
A
By either killing pathogens, or removing them from the water.
18
Q
When would knowledge on water purification be useful?
A
In remote regions tap water is not always avaliable, meaning you may have to purify water from lakes/streams before drinking it.
19
Q
What measures are used by Sydney Water to ensure the water provided to households is clean?
A
Reservoirs are usually surrounded by national parks. Water is filtered. Small amounts of chlorine are present. Regular monitoring of filters and water quality.
20
Q
What is meant by “pure” tap-water?
A
Tap-water must be free from substances harmful to health.
21
Q
What is meant by “pure” labatory water?
A
Laboratory water must from free from ALL impurities.
22
Q
How is fluoride used in water purification?
A
Fluoride is added to tap water in small amounts to aid in the maintenance of dental health.
23
Q
How will low levels of trace-elements in water be harmful to tap-water?
A
Low levels of trace elements such as aluminium, iron and manganese occur naturally in water, and may cause problems of staining and taste.
24
Q
What are trihalomethanes?
A
Trihalomethanes are by-products of the disinfection process in water purification.
25
What is turbidity?
Turbidity is a measure of the quantity of suspended particles in the water, which may make it appear discoloured or murky. These particles could harbour pathogens.
26
What are coliforms?
Coliforms are bacteria, such as Escherichia coli, that are usually associated with faecal contamination
27
How are coliforms used in assessing water quality?
They are used as a scientific indicator of the cleanliness of drinking water as the presence of coliforms is an indicator that other diseases that can be transmitted by faecal contamination are also present. These bacteria are killed by chlorine.
28
What is epidemiology?
Epidemiology is the application of scientific methods to the study of disease in populations for the purpose of prevention and control of disease.
29
What are 7 things considered in an epidemiological study?
A description, or definition, of the disease.
Possible causes of the disease.
Occurrence and transmission of the disease
Consideration of risk factors for various members in a population, that is, who is more likely to be affected by the disease.
Control of the disease, for example, whether an affected individual should be isolated from others.
Prevention of the disease, e.g. whether a special diet might prevent expression of the disease.
Possible elimination of the disease.
30
What is the endemic level of disease?
The endemic or baseline level of disease for a given population is the typical rate at which a disease occurs. This endemic level will be specific to each population and each type of disease.
31
What is the baseline level of disease in a population?
The endemic level of disease.
32
What is an epidemic?
A sudden increase in the prevalence of disease above the endemic rate.
33
What is the sudden increase in the prevalence of disease above the endemic rate known as?
An epidemic.
34
What is an outbreak?
A sudden increase in the prevalence of a disease above the endemic rate within a small or specific geographical area.
35
What is a sudden increase in the prevalence of a disease above the endemic rate within a small or specific geographical area?
An outbreak.
36
What is a pandemic?
A sudden increase in the prevalence of disease across multiple countries and/or continents.
37
What is a sudden increase in the prevalence of disease across multiple countries and/or continents?
A pandemic.
38
What is disease incidence?
The number of new cases of a disease diagnosed, usually expressed in a time frame.
39
What is the number of new cases of a disease diagnosed, usually expressed in a time frame?
Disease incidence.
40
What is disease prevalence?
The total number of cases of a disease in a population at a given time, or over a given period of time.
41
What is the total number of cases of a disease in a population at a given time, or over a given period of time?
Disease prevalence.
42
How does globalisation impact transmission of disease?
As globalisation allows people to be less confined to small geographical areas, disease transmission can occur at a higher rate.
43
What are the 3 conditions that affect a pathogen's transmissibility?
The pathogen's mode of transport.
Timing of the contagious period.
The pathogens characteristics.
44
What are the conditions that affect the host population's susceptibility?
Level of immunity.
Population density.
45
What are 4 modes of transport for a pathogen?
Airborne, water and food, blood/bodily fluids, vectors.
46
Assess the transmissibility of airborne pathogens.
They tend to be easily transmissible, as they are often difficult to intercept, and due to water droplets or vapour being exchanged during breathing, it makes them the most likely to cause epidemics.
47
What are 4 examples of diseases with airborne pathogens?
Covid 19, Measles, TB, Influenza
48
What is an example of a water-borne disease?
Cholera.
49
Assess the transmissibility of water-borne diseases.
Diseases spread through water can produce epidemics, although sanitary precautions are able to be taken, in order to prevent them.
50
How likely are diseases spread via blood/bodily fluids to cause an epidemic?
Diseases spread via blood/bodily fluids are able to cause epidemic, although they require close contact to spread, making transmission possible to slow.
51
What are 2 examples of diseases spread via blood/bodily fluids?
HIV/AIDS, or ebola.
52
Assess the likelihood of a vector-borne pathogen becoming a pandemic.
Vector-borne pathogens tend to be limited to their geographical range, so they are more likely to develop into contained epidemics, rather than pandemics.
53
What are 2 examples of vector borne diseases?
Malaria and dengue fever.
54
What effect do diseases with early contagious period have on transmission?
Diseases that can be transmitted before someone is aware they’re infected can spread extremely rapidly, as the individual is unlikely to be taking the necessary precautions to prevent the transmission of disease.
55
What are 3 diseases with early contagious periods?
Covid, chicken pox, influenza.
56
What affect do diseases with late contagious periods have on transmission?
When the infectious period occurs later in the infection, victims are sicker by the time they can pass it on, making it less likely to be transmitted, as the individual is aware of the disease, and likely making precautions to prevent its spread.
57
What is an example of a disease with a late contagious period?
Smallpox.
58
What to characteristics make pathogens more likely to cause an epidemic?
High transmissibility, virulence, and rapid mutation rate.
59
What happens if transmission and virulence are too low?
If transmissibility or virulence is low, pathogens spread more slowly and are less of a threat to a population.
60
What happens if virulence is too high?
Spread of disease is also slower if virulence is too high, as hosts are likely to die before spreading the infection to other organisms.
61
How does a rapid mutation rate help a diseases' transmissibility?
Rapid mutation rate makes pathogens dangerous, as new vaccines and previous infections may not protect against new variants, prolonging the pathogen’s spread.
62
What type of pathogen is most likely to cause an epidemic?
Viruses.
63
Why are viruses the most likely pathogen to cause an epidemic?
Due to rapid mutation and exceptionally high replication rates.
64
Which are the most dangerous viruses?
RNA viruses.
65
Why are RNA viruses the most dangerous viruses?
They evolve rapidly into new variants through bypassing the host cell’s editing process. They begin replicating as soon as they enter a cell’s cytoplasm.
66
Why are DNA viruses less dangerous?
They must be transcribed into RNA in the nucleus before replication can begin. This slows their evolution as the host's cell DNA-editing features correct many mutations, reducing the number of new variants.
67
What is health?
The overall wellbeing of an individual. This includes physical, mental, and social wellbeing.
68
What is disease?
Any condition that disrupts the normal functioning of an organism. It usually causes symptoms, ranging from mild to severe.
69
What is infectious disease?
A disease that can be spread from one organism to another and is caused by a pathogen.
70
What is a pathogen?
A causative agent of infectious diseases. Usually an organism, however some pathogens are non-cellular.
71
What are the two types of parasite?
Ectoparasites and endoparasites.
72
What are ectoparasites?
Parasites that live outside of the host’s body, usually on its skin.
73
What are endoparasites?
Parasites that live inside the host's body.
74
What type of adaptations might an endoparasite have?
Attachment organs such as hooks or suckers to fasten themselves to their host’s intestine.
75
What is an example of an endoparasite?
Most are types of flatworms, such as tapeworms and flukes.
76
What are 5 examples of ectoparasites?
Leeches, fleas, ticks, lice, and mites.
77
What are 2 non-cellular pathogens?
Viruses and prions.
78
What are 6 examples of pathogens?
Viruses, bacteria, fungi, prions, protozoa, and macroscopic parasites.
79
What cell type do bacteria have?
Prokaryotic.
80
What cell type do viruses have?
Non-cellular.
81
What cell type do fungi have?
Eukaryotic.
82
What cell type do protozoa have?
Eukaryotic.
83
What cell type do parasites have?
Eukaryotic.
84
What cell type do prions have?
Non-cellular.
85
Are bacteria unicellular or multicellular?
Unicellular.
86
Are fungi unicellular or multicellular?
They can be either.
87
Are protozoa unicellular or multicellular?
Unicellular.
88
Are parasites unicellular or multicellular?
Multicellular.
89
What is the typical size of bacteria?
1 µm
90
What is the typical size of fungi?
4 µm
91
What is the typical size of viruses?
80 µm
92
What is the typical size of protozoa?
50 µm
93
What is the typical size of prions?
2-5 nm
94
What is the typical size of parasites?
µm
95
Describe the structure of bacteria.
Prokaryotic with cell walls. DNA present but no nucleus. Often has structures to aid mobility.
96
Describe the structure of fungi.
Eukaryotic cells with cell walls. DNA is inside a nucleus. Yeasts are often round in shape, but fungi can form irregular branching shapes.
97
Describe the structure of protozoa.
Eukaryotic cells with no cell wall. Often has structures to aid mobility.
98
Describe the structure of viruses.
A protein outer case protects internal nucleic acid (can be DNA or RNA).
99
Describe the structure of prions.
A protein.
100
Describe the structure of parasites.
A wide variety of multicellular eukaryotic organisms.
101
What are 4 examples of bacterial diseases?
Cholera
Tuberculosis
Tetanus
Pneumonia
102
What are 3 examples of fungal diseases?
Thrush
Ringworm
Tinea/athlete's foot
103
What are 4 examples of diseases caused by protozoa?
Malaria
African sleeping sickness
Dengue fever
Giardiasis
104
What are 5 examples of viral diseases?
Common cold
Influenza
Chicken pox
HIV/AIDS
Bird flu
105
What are 4 examples of diseases caused by prions?
Mad cow disease
Creutzfeld-Jacob
Disease (CJD)
Kuru
106
What are 3 examples of diseases caused by parasites?
Heartworm
Tapeworm
Varroa mite
107
What was the socially accepted theory on the cause of disease before the 19th Century?
The idea of disease being caused by “evil spirits” or “bad air”.
108
According to miasma theory, how did microbes form?
Although microbes had been discovered two centuries ago, microbial growth was believed to originate by spontaneous generation.
109
What is miasma theory?
The idea that disease was caused by "evil spirits" or "bad air".
110
What is spontaneous generation?
The process by which living organisms develop from non-living matter.
111
Before germ theory, how was the concept of spontaneous generation justified?
This theory was widely accepted in society because it aligned with religious beliefs that God created life, and so it didn’t seem inconceivable that life could arise from non-living things. Many believed in spontaneous generation because it explained such occurrences as the appearance of maggots on decaying meat.
112
What is germ thoery?
The germ theory of disease, developed and popularised in the 19th century, proposes that many diseases are caused by microscopic organisms (germs) that invade the body and disrupt its normal functions.
113
What piece of equipment was a catalyst in the development of germ theory?
The microscope, as it allowed scientists to view microscopic organisms.
114
Who was Robert Koch?
Robert Koch lived around the same time as Louis Pasteur and lived in Germany, studying the cause and transmission of disease. He developed new equipment and techniques that allowed bacteria to be studied, many of which are the basis of biotechnology today.
115
Which diseases did he discover the causative bacteria of?
Anthrax, tuberculosis, and cholera.
116
What are Koch's postulates?
Conditions that can be used to determine the specific pathogen that causes a disease.
117
What are the 4 Koch's postulates used to determine pathogens?
1. The suspected causative agent must be absent from all healthy organisms, but present in all diseased organisms.
2. The causative agent must be isolated from the diseased organism, and grown in pure culture.
3. The cultured agent must cause the same disease when inoculated into a healthy, susceptible organism.
4. The same causative agent must then be reisolated from the inoculated diseased organism.
118
Why are Koch's postulates important?
(1) Established a systematic method for identifying the cause of infectious diseases.
(2) Linked specific microbes to specific diseases.
(3) Provided scientific evidence for the germ theory of disease.
(4) Formed the foundation of modern infectious disease research and epidemiology.
119
What are 3 limitations of Koch's postulates?
(1) Originally designed for bacteria
(2) Asymptomatic carriers
(3) Ethical concerns
120
Why is the fact that Koch's postulates being originally designed for bacteria provide limitations in epidemiology?
Viruses:
- Cannot grow outside a host cell (can't be cultured in pure form).
- Some viruses cause disease only in humans, making animal testing unethical or impossible.
Fungi, parasites, and prions:
- Some are hard to culture or have complex life cycles.
- May not cause disease in every host they infect (violates Postulate 3).
121
Why do asymptomatic carriers provide a limitation for the application of Koch's postulates?
Some infected individuals show no symptoms, which complicates the idea that the pathogen must always cause disease.
122
Why do ethical concerns provide a limitation for the application of Koch's postulates?
Postulate 4 requires infecting a healthy host, which is unethical in humans.
123
What did Pasteur discover about fermentation?
He discovered that live microbes (yeast) caused fermentation and that when much smaller microbes (bacteria) were present, acetic acid was produced, making it sour.
124
What process did Pasteur use to prevent fermentation in wine?
In the 1860s, he developed a method to prevent wine spoilage called pasteurisation. This involved heating the wine to kill microbes and then letting it cool.
125
What is pasteurisation?
Pasteurisation is a process of heating a liquid, to a specific temperature for a set time to kill harmful bacteria without significantly altering the food's taste, texture, or nutritional value.
126
What did Pasteur's observations of diseases in wine lead him to?
That microbes could also cause disease in humans.
127
Who was Pasteur inspired by?
Surgeon Dr Joseph Lister, to develop antiseptic methods for use in surgery and to treat wounds.
128
Provide an overview of Pasteur's experiments with wine, and what it led him to discover.
Through his examination of wine “disease”, Pasteur discovered that microbes were responsible for wine becoming sour. He then developed methods to prevent wine spoilage through killing microbes with heat. This helped Pasteur him infer that microbes caused disease in humans and that germ theory was correct.
129
What are 3 products that pasteurisation can be used for?
Beer, wine, and milk.
130
What was the objective of Pasteur's experiments with swan-necked glasses?
To disprove the theory of spontaneous generation → the idea that life can arise from non-living matter.
131
Describe the experimental set up of Pasteur's experiments with swan-necked glasses.
Pasteur used swan-necked (S-shaped) flasks containing nutrient-rich broth.
The neck of the flask was curved to allow air in but prevent dust and microorganisms from reaching the broth.
132
Describe the procedure of Pasteur's experiments with swan-necked glasses.
The broth was boiled to kill any existing microorganisms (sterilisation).
The flasks were then left open to air through the swan neck, but no dust or microbes could reach the broth due to the curve.
133
Describe the observations of Pasteur's experiments with swan-necked glasses.
The broth in the swan-necked flasks remained sterile (clear, no microbial growth) for a long time.
When the neck was broken off or the flask was tilted so the broth contacted trapped dust in the neck, microbial growth appeared.
134
Describe the conclusion of Pasteur's experiments with swan-necked glasses.
Microorganisms come from external contaminants (like dust), not from spontaneous generation.
Air alone does not cause microbial life to appear in sterile broth.
135
What was the impact of Pasteur's experiments with swan-necked glasses.
Strongly supported the germ theory of disease.
Disproved spontaneous generation.
Revolutionised practices in medicine, food preservation, and microbiology.
136
Provide an overview for Pasteur's work in the silkworm industry.
Discovered microbes were the cause of a disease in silkworms that was threatening the silk industry.
Developed a method to kill the microbes → thus preventing the disease and saving the silk industry
137
Provide an overview for Pasteur's work in vaccines for chicken cholera.
Grew bacteria that caused cholera in chickens.
Injected chicken with cholera bacteria cultures that had been left idle for some time.
Found that these chickens could then be injected with fresh chicken cholera bacteria and not become diseased.
138
Provide an overview for Pasteur's work in vaccines for anthrax in farm animals.
Publicly demonstrated in multiple farm animals that injections of weakened anthrax bacilli protected the animals from anthrax when later injected with virulent anthrax bacilli.
139
Provide an overview for Pasteur's work in vaccines for rabies.
Could not identify the microbe that caused rabies.
Experimented by injecting animals with body fluids from other animals with rabies and found he could prevent rabies developing in them.
Successfully used this vaccine on humans (the initial test subjects had been bitten by rabid animals and were expected to soon die).
140
What is pathogen adaptation?
Specialised feature of a pathogen which increases its ability to attack a host and invade a population.
141
Why is pathogen adaptation advantageous?
The ability to survive in different host species with an adaptation that is highly advantageous to pathogens because it increases their chances for survival and circulation.
142
