Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pathobiology of Human Disease > Transmissible disease > Flashcards

Transmissible disease Flashcards

1
Q

What is a transmissible disease?

A

Transmissible diseases are transmitted among people by disease-causing microorganisms. Also known as pathogens
Examples: viruses, bacteria, fungi, parasites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are contagious diseases?

A

Are a subset that can be passed on by direct contact with an infected individual (or material from an infected individual). This contrasts with agents which require secondary host species or specific route of infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Are there exceptions to the rules of transmissible diseases?

A

There are very few exceptions e.g. Prion diseases which are caused by misfolded proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where do transmissible diseases cause greatest mortality?

A

Cause greatest mortality and disability in Africa and Asia
In Europe and North America, the greatest deaths are from CVD and cancer. Most transmissible disease mortality in elderly patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are examples of the infectious microorganisms?

A

Viruses: e.g. SARS-CoV-2, influenza (flu)
Bacteria: e.g. E. coli O157, Staph. aureus
Parasites: e.g. Cryptosporidia, Schistostomes
Fungi: e.g. aspergillus, candida

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the main routes of infection?

A

Normal contact: Microorganisms live or can survive on skin and other surfaces

Airborne: Microorganisms can be passed on from infected individual by coughing sneezing and survive in aerosol form

Vector or alternative:
Some microorganisms live in a secondary animal host from which they then passes to further people
Mostly transmitted by insects
E.g. Plasmodium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the other routes of infection?

A

Body fluids: Some micro-organisms require direct exchange of body fluids e.g. sexual transmission, needle sharing etc e.g. HIV

Consuming food and water:
Microorganisms are passed on in contaminated water and food. Many cause intestinal infections ‘food poisoning’ e.g. E. coli O157

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the most important evolved characteristic of pathogens?

A

Killing off a host (or host species) seems likely to be bad for a pathogen and limits expansion
Therefore, it seems to be an evolutionary benefit to minimising the impact on the health of the host species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are zoonotic diseases?

A

Many human pathogens, especially viruses, have a reservoir in other species but can transfer to humans. These are zoonotic diseases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How else can pathogens evolve?

A

Pathogens do evolve to infect new hosts (e.g. humans) and this sometimes causes great disease burden/mortality but when evolving in a host species, selection is to maximise spread but minimise impacts on the host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the ebola virus disease?

A

Ebolavirus: Quite large filamentous virus (800-1400nm long) with single stranded 7 gene RNA genome
Replicates in many different cell types including cells in the blood (e.g. monocytes)
Also known as Ebola Haemorrhagic fever and related to Marburg Virus (Marburg fever)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the mortality rate of ebola virus?

A

Very high rapid mortality. 30-90% and takes 1-2 weeks
Recent lengthy outbreak in West Africa (2014-2016). 29,000 infected, 11,000 deaths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is ebola virus transmitted to humans?

A

Human to human transmission by indirect contact with any body fluids. Viruses can persist dried for several hours, and wet (e.g. blood) for several days. Dead bodies remain infectious for several days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is leprosy

A

Long term bacterial infection by Mycobacterium leprae. Unculturable obligate intracellular parasite
Transmissible but only modestly contagious. Spread by close frequent contact with untreated cases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the symptoms of leprosy?

A

Initial symptoms are mild. Infection (particularly of Schwann cells) may cause no symptoms for several years. Single or multiple skin lesions and sensory loss at lesions. Severe cases result in extensive nerve and skin damage, muscle weakness and deformity due to unnoticed infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How slow is the progression of leprosy?

A

Bacterial growth and disease progression is slow. Incubation period is approx 5 years
Treatment (multiple antibiotics) is highly effective and worldwide disease burden is reducing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is lyme disease?

A

Bacterial infection by Borrelia burgdorferi, a Spirochete bacterium. A few micro meters long
Transmission is by tick bites from infected deer ticks (Zoonosis). A few mm long. No evidence for human to human transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the symptoms of Lyme disease?

A

Initial symptom is a bulls eye rash (4-8 days)
If untreated, infection spreads through body causing headaches, joint pain, fever, facial palsy. Can persist as severe chronic illness affecting multiple organ systems
Antibiotic treatment is usually successful at earlier stages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is HPV?

A

e.g. Human Papilloma virus (HPV)
Many types of HPV infect different epithelia in mouth, throat, cervix and anus
HPV is a common sexually transmitted infection, causing genital warts. Almost all cases of HPV have little or no serious independent health impact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do HPV’s influence diseases such as cancer?

A

The genital warts caused by HPV can be viewed as pre-cancerous lesions and increase the risk of genital cancers, particularly cervical cancer. Cervical cancer is almost always linked to HP16 or HPV18

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the common cold?

A

The common cold can be viewed as the most frequent infectious disease in humans
It is a viral infection of upper airways in which similar symptoms can be caused by many different viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How many viruses can cause the common cold?

A

Evidence shows several hundred viruses can cause colds. Rhinoviruses are the most common. There is overlap with symptoms of influenza virus infection, but influenza is generally substantially more severe
There is no effective treatments for infections. Painkillers can alleviate symptoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is vaccination?

A

Vaccination is the exposure of individuals to components or non-infectious types of a disease causing pathogen. If successful, this exposure to antigens from the pathogen causes the immune system to develop adaptive immunity to the real pathogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is an example of a vaccine?

A

Smallpox vaccine: In the late 18th century, Edward Jenner showed that exposure to material from cowpox, a related but mild infection, provided later protection from exposure to smallpox
Until vaccination, smallpox killed a substantial fraction of European populations (10%). The last reported case of smallpox worldwide was in 1977.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is herd immunity?

A

If most of a population are vaccinated and immune to an infection, the probability of transmission and a sustained outbreak of the disease is greatly reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are some vaccine types?

A

Vaccine types include inactivated (e.g. heat), attenuated (live but non-virulent) and component/subunit (e.g. individual proteins) vaccines, and even mRNA

27
Q

What are secondary infections?

A

A secondary infection is one occurring in someone already carrying an infectious disease
In some cases it is secondary infections that directly cause the greatest ill effects
e.g. HIV/AIDS damages the immune system, and patients greatest problems are then caused by secondary infections, such as pneumonia

28
Q

Are transmissible diseases easy targets for therapy?

A

Because communicable diseases are generally caused by single microbial species which are evolutionary distant from humans, it has been easier to develop drugs to treat them than to treat complex complex non-communicable disorders such as diabetes and cancer

29
Q

What successes are there for therapy in communicable diseases?

A

In almost all cases, the microbes have (and rely on) proteins which are absent from humans or at least very different and allow drugs which will hit the microbe but not the patient

30
Q

What is Prion disease?

A

Rare progressive neurodegenerative diseases caused by the transmission of a misfolded protein
With no genetically encoded pathogen

31
Q

What are some examples of Prion disease?

A

Bovine spongiform Encephalopathy (BSE/Mad cow disease), Scrapie (sheep)

And in humans:
Creutzfeldt-Jakob disease (CJD)
and variant CJD (acquired by ingestion)
Kuru (associated with cannibalism)

32
Q

What are mammalian prion proteins?

A

Are abberant non-functional misfolded proteins which upon exposure, are able to induce certain specific healthy proteins, including host Prions, to undergo the same mis-folding and aggregation. Exposure usually by ingestion, but is very inefficient

33
Q

What does prion protein mis-folding cause?

A

Causes the accumulation of prion protein aggregates, neuronal cell death and eventually the spongy appearance of brain tissue characteristic of victims of these diseases

34
Q

What is the Creutzfeldt-Jakob disease?

A

Mostly sporadic. In these cases the trigger for prion protein aggregation is uncertain
This can be genetic, caused by mutations in the PrP gene which encode unstable prion protein susceptible to aggregation

35
Q

What are viruses?

A

Very small microorganisms (30-500nm)
Viruses can live only as genetic parasites by infecting living host cells

36
Q

What host cells do viruses infect?

A

Host cells can range from human cells, to those of other animals, plants and bacteria. Each virus has a specific host range

37
Q

What is the structure of viruses and how do they reproduce?

A

They are small particles containing genetic material surrounded by a protein coat
They reproduce by introducing their genetic material into new host cells, replicating this genetic material and producing new proteins to package new virus particles. They can be very complex or very simple

38
Q

What is the Tobacco Mosaic virus?

A

Filamentous virus (300nm long, 18nm diameter) with single stranded 4 gene RNA genome
Replicates in many different plant cell types
The coat protein is capable of energetically favourable self assembly

39
Q

What does the virus particle consist of?

A

Virus particle has 2130 molecules of the coat protein and an RNA genome of 6300 bases

40
Q

What does a 4 gene genome consist of?

A
  • Replicase (RNA helicase and methyltransferase)
  • RNA dependent RNA polymerase
  • Movement protein (assists viral entry into host cell)
  • Coat (Capsid) protein
41
Q

What are helical viruses?

A

Some RNA viruses have helical capsids
The capsid looks cylindrical under the electron micrograph with its protein molecule building blocks stacked in a helical array
The RNA genetic material is wound around the inside
e.g. Tobacco Mosaic virus

42
Q

What is the usual structure of the capsid of viruses?

A

Isosahedral or cylindrical helix construction with subunits provides high symmetry and reduces the number of different proteins required for subunit construction

43
Q

What does a icosahedron structure provide?

A

Provides a mechanically strong structure enclosing a maximum volume- it is the best way to obtain a shell of equivalently bonded identical structures
The symmetry and simplicity of viral capsid structures allows their subunits to spontaneously self-assemble into virions

44
Q

Do giant viruses exist?

A

Almost all viruses are too small to be seen by light microscopy (30-300nm) and are much smaller than bacterial cells
A few viruses are much larger e.g. Pandoravirus infect amoeba and are almost 1 micrometer long and have a genome of 2-2.5 million base pairs and > 2000 protein coding genes

45
Q

What blurs the boundaries between cellular and viral life?

A

Since the simplest bacterial cells also can only live as parasites of other larger cells (e.g. Mycoplasma pneumoniae), this blurs the boundaries between cellular and viral life

46
Q

What is the basic virus structure?

A
  • Viral RNA or DNA protein coat (capsid)
  • Nucleoprotein
  • Envelope and matrix
  • Glycoprotein peplomers
47
Q

What is a single infectious virus particle called?

A

A virion

48
Q

What is the nucleoprotein and envelope of a virus?

A

Nucleoprotein- an inner layer of protein bound to the nucleic acid
Envelope- an outer lipid bilayer membrane- present for many animal viruses but very few plant viruses

49
Q

What is the matrix and peplomers of viruses?

A

Matrix- For enveloped viruses, this an additional protein shell between the capsid and envelope
Peplomers- (glyco) protein spikes protruding from the virion surface

50
Q

What is HIV?

A

Human Immunodeficiency Virus (HIV) is a human infective retrovirus which causes acquired immunodeficiency syndrome (AIDS)
HIV virus particles are rapidly degraded in the environment. Efficient transmission through bodily fluids

51
Q

What cells does HIV infect?

A

HIV infects cells of the human immune system
Untreated HIV infection causes progressive failure of the immune system resulting in secondary infections and cancers and commonly death after 5-15 years

52
Q

What is the UK incidence of HIV?

A

The UK incidence is estimated at 100,000 carriers (2015) and approx 600 deaths and 6000 new cases annually

53
Q

What does a HIV virion comprise of?

A

spherical (100nm) particle consisting of:
- An outer lipid envelope studded with 72 glycoprotein spikes
- A matrix made of p17 protein molecules
- A capsid of p24 protein organised as a hollow truncated cone
- Human cyclophillin A protein molecules bound to p24
- 2 copies of a the single stranded viral RNA genome
- A nucleocapsid sheath of p9 protein complexed with the RNA
- Several copies of 3 enzymes: (a) HIV reverse transcriptase (b) HIV protease and (c) HIV integrase

54
Q

How is the HIV genome organised?

A

The HIV genome is single stranded RNA and:
- Possesses 9 genes
- Spans about 9.2 kb over the regions encoding the genes
- Has some overlapping and fragmented genes

55
Q

What viruses are difficult to eradicate?

A

Viruses which incorporate a DNA copy of the viral genome into the host chromosomes are very difficult for the immune system to eradicate if they are dormant- e.g. herpes virus infections
This includes some DNA viruses and retroviruses such as HIV

56
Q

What is a retrovirus?

A

A retrovirus is a virus that has an RNA genome and converts it to a DNA copy before inserting it into a host cell DNA genome

57
Q

How are RNA viruses unique?

A

RNA viruses are characteristically highly changeable through mutation which allows them to escape the immune system
Many viral RNA-dependent RNA polymerases have no proofreading capability

58
Q

What is the HIV replicative cycle?

A
  1. Adhesion
  2. Host cell entry
  3. Uncoating
  4. Reverse transcription of RNA genome
  5. DNA genome copy integration
  6. Replication and gene expression
  7. Viral RNA export
  8. Viral protein synthesis
  9. Virion packaging
  10. Virion release
59
Q

What is the therapy for HIV?

A

Viral RNA is not stable in host cells in the long term
Several steps in the replicative cycle can be targeted by different drugs
Drug classes:
- HIV entry inhibitors
- Reverse transcriptase inhibitors
- HIV protease inhibitors
These are now used in combination

60
Q

What is HIV reverse transcriptase?

A

An RNA dependent DNA polymerase
It copies the HIV genome using its RNA genome as a template and creating a DNA copy
Reverse transcriptase (RT) synthesises DNA at its polymerase catalytic site using the HIV RNA genome as a template
HIV reverse transcriptase also destroys the HIV RNA genome template after it has passed through its polymerase active site

61
Q

What is the anti-HIV drug AZT?

A

A competitive inhibitor of Reverse Transcriptase
AZT mimics nucleosides which can be incorporated into DNA

62
Q

How does phosphorylated AZT work?

A

Phosphorylated AZT binds to the catalytic site of Reverse Transcriptase, but is a poor substrate and if incorporated into DNA, the N3 group cannot be extended, causing chain termination. If HIV reverse transcription is interrupted, it cannot be restarted as HIV genome will have been degraded as it is copied

63
Q

What are the developing anti-HIV drugs?

A

Next generation Nucleoside Reverse Transcriptase Inhibitors (NRTIs) are
- Better inhibitors or HIV reverse transcriptase
- Are more rapidly phosphorylated into their active form and
- Have fewer side effects due to inhibition of host cell DNA polymerases

Pathobiology of Human Disease (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions