Viruses Flashcards
(54 cards)
1
Q
What is the size of viruses
A
~100 nm
2
Q
What is a virus
A
- It is an obligate intracellular parasite
- Their genetic material (DNA or RNA) surrounded by a protein coat and sometimes a lipid envelope
3
Q
Are viruses alive
A
- No
- They cannot grow or divide
- Not capable of energy production
- They cannot think
4
Q
Structural features of viruses
A
- Viral genome -DNA or RNA
- Viral Capsid- A protein coat
- A lipid bilayer with glycoproteins- can help virus bind to cells
5
Q
What is the difference between enveloped and non-enveloped viruses
A
- Enveloped viruses are more fragile than non-enveloped viruses
- Envelopes can be easily destroyed by hand gel
6
Q
How are viruses classified
A
Order-Family-(Subfamily)-Genus-Species
(-Strains/subtypes-Variants)
7
Q
How do viruses spread
A
- Horizontal transmission = person to person
- Vertical transmision = mother to foetus
8
Q
What are some transmission mechanisms of viruses
A
- Direct contact
- Aerosols
- Contaminated surfaces
- Exchange of body fluids
- Insects
- Contaminated food and water
9
Q
How to get rid of viral diseases
A
- Antivirals - some exist, hard to develop antivirals that aren’t toxic (because viruses are in our cells anitviral would have to kill our cells too)
- Vaccination - provides a longer-term solution (inactived, conjugate, genetic, live attenuated, subunit)
10
Q
How long do vaccines take to create
A
Usually take ~10 years
11
Q
How were COVID vaccines developed much quicker
A
- (9 months)
- Funding was quickly aquired
- clinical trials were done more efficiently and therefore much faster
12
Q
Name some examples of non-pharmaceutical interventions
A
- Isolation of the infected
- Restriction of animal/human movement
- Slaughter of infected animals
- Control of vectors (controversial)
- Education and public health messaging
13
Q
What is a virome
A
- All the viruses living with one organism or environment
- Part of the microbiome
- The virosphere is the sum of all viruses on Earth
14
Q
How much of the human body is our own body cells
A
- Only ~43% of the cells that compose you are human
- ~1.10^+15 cells are viruses
15
Q
How much of human DNA is from virus
A
- 5-8%
- of our DNA is made of virus genetic material (endogenous retrovirus)
- acquired during evolution through infection of germ cells
16
Q
How do viruses infect us
A
- Acute infection - cold, flu, fast acting
- Long-term infections - with you forever, herpes, HIV, hepatitis
- Oncogenesis - viruses that cause cancer, hepatitis, HIV
- Economic impact - agriculture, days of work/school
17
Q
How do we find viruses that we don’t know about yet?
A
- Metagenomics - collecting DNA to screen
- All the genetic material is sequenced and sections that ‘look like viruses’ are examined further
18
Q
Why should we continuously look for new diseases
A
- Causes of human disease - to prevent new diseases
- Potential zoonotic viruses-pandemic
- Identifying good viruses - phages
19
Q
What is zoonosis
A
- When a virus ‘jumps’ from an animal to a human
- 75% of newly emerging infectious diseases are zoonoses
- Zoonosis can result in a new virus i.e. SIV to HIV
- Examples: Avian influenza, SARS-CoV-2, nipah, hendra
20
Q
What is deadend transmission
A
- Occurs when an organism, or dead-end host, prevents the transmission of a parasite to a definitive host
21
Q
5 points
Why is it expected that epidemics and pandemics will occur with more frequency
A
- globalisation - people flying to different countries more often carrying viruses
- melting permafrost - contains viruses
- increased agriculture - higher chance of zoonosis
- anti-viral resistance
- deforestation - destruction of animal habitats causes animals to have increased unnatural interactions and with humans, highwer chance of zoonosis
22
Q
How do we study viruses
A
- Cell lines
- Embryonated eggs
- In vivo (live animals)
23
Q
What are the advantages of using cell lines to study viruses
A
- Easy to see the impacts/effects of the virus on the cells
- Can test on lots of different cells to see which species can get infected
24
Q
What are the disadvantages of using embryonated eggs to study viruses
A
- People can be allergic to eggs so cannot be used to create vaccines
- Ethincally bad
25
What are the disadvantages of using in vivo to study viruses
- Ethically bad
26
What are the 4 ways viruses can be beneficial
1. Oncolytic viruses
2. Alternatives to antibiotics
3. Gene therapy
4. Biological control - alternative to pestisides
27
What are oncolytic viruses
- Destroy cancer cells
- Viruses can be engineered to only infect cancer cells and cause them to die
28
How can viruses be alternatives to antibiotics
- Bacteriophages
- They can infect bacteria
29
How can viruses be used in gene therapy
- Retroviruses can be engineered with correct sequence of RNA --> DNA to integrat into human DNA to cure genetic dieases
30
How can viruses be used as an alternative to pestisides
- Viruses can be engineered to only infect and kill pests that destroy wheat/rice etc...
31
What is viral pathogenesis
- The process by which a virus causes a disease
32
What is disease a combination of
- Effects of the viral infection and replication
- Effects of host response (immune system)
33
What does virulence mean
- ‘Virulence’ refers to how damaging a pathogen is to the host
- The pathogenicity of a virus is determined by its virulence
34
What can virulence be determined by
- Virus titre (how much virus accumulates in a host)
* Time to death
* Time to signs of disease
* Measurement of signs i.e. fever, weight loss, lesions, etc.
35
What are 5 factors that affect virulence
1. Route of infection
2. Dose of infection (amount of virus)
3. Age
4. Sex
5. Susceptibility
36
What are the 5 things a viruse must do to cause disease
1. Gain entry to the host
2. Enter the correct target cells (only some have right receptors)
3. Replicate in the host
4. Trigger the immune response
5. Evade the immune system long enough to replicate & infect other cells
37
# 6 steps
How do viruses replicate
1. Viral attachment/endosytosis
2. Uncoating - inserting the genetic material into host cells nucleus
3. Genome replication - inserting viral DNA into host DNA
4. Translation - mRNA --> unfolded proteins
5. Assembly - proteins --> golgi
6. Leave the host to infect other hosts
38
What machinery do viruses use to replicate
Enzymes, Ribosomes, tRNAs
39
What raw materials do viruses use to replicate
Nucleotides, Amino acids, Energy
40
# 4
What non-structural proteins do viruses need to use to assemble
1. Enzymes to replicate viral genome
2. Needed immediately and in small amount
3. Required only inside the infected cell
4. Will not become part of the virus
41
# 3
What structural proteins do viruses need to use to assemble
1. Needed to form the progeny virus particles
2. Needed in large quantity
3. Only needed after genome is replicated
42
How are viruses detected by the host
- Pattern Recognition Receptors (PRRs)
- Host sensors that detect pathogens
1. TLRs (Toll-like receptors),
2. RLR (RIG-I-like receptors),
3. Cytosolic DNA receptors (CDR)
- They detect parts of the virus and trigger the innate immune response.
43
Define what are signs
Signs are observable effects of an infection
Headache, fatigue, fever, rash
44
Define what are symptoms
Symptoms are experienced by the patient
High blood pressure, protein in urine, altered white blood cell count
45
Which inmmune cells are required to fight viruses
1. Interferon
2. Cytokines
46
What does incidence mean
Incidence = the number infected in a population at a given time
47
What does morbility mean
Morbidity = the number of people who are sick in a population
48
What does mortality mean
Mortality = the number of deaths in a population
49
What does case fatality rate mean
Case Fatality Rate (CFR) = no. of deaths/confirmed infections
50
What does infection fatality rate means
Infection Fatality Rate (IFR) = no. of deaths/no. of infections
51
Why is it hard to calculate IFR
- It is hard to estimate how many people get infected
52
Facts about measles
1. Likely evolved with the domestication of cattle (11th century)
2. Measles virus requires larger human populations
3. Spread around the world
4. Killed many Native Americans in 16th century
5. One of the most infectious viruses R0=16
53
What does R0 mean
How many people 1 infected person can on average infect
54
Facts about SARS
1. Severe acute Respiratory syndrome
2. Emerged in Guangdong Province, China late 2002
3. Origin suggested as horseshoe bat-civet cat-human
4. 8,096 cases; 783 deaths
5. Symptoms: headache, fever, aches, lethargy, dry cough, breathlessness
