12 Viruses (4) Flashcards
Where do respiratory tract viruses tend to replicate?
Cells of ANY part of the respiratory tract
from the nasal passages down to the lower lung bronchioles
T or F: Respiratory viruses are usually not a problem in developing countries, but a big concern in the developed world due to resistance.
F
Low mortality rate in the developed world due to respiratory viruses, but a big concern in developing countries
Respiratory tract viruses tend to have a _______ distribution.
seasonal
Name two ways respiratory viruses can be transmitted.
- Inhalation of aerosols
2. Contact w/ contaminated surfaces
Name a v. popular respiratory virus.
Influenza virus
What is the structure of the influenza virus?
Enveloped RNA virus w/ a “segmented” genome
What’re the two kinds of spike proteins on the envelope of influenza?
- Neuraminidase (N)
2. Hemagglutinin (H)
What does neuraminidase (N) (type of Flu spike protein) do? (2)
- DEGRADES mucus layer on respiratory epithelial cells > allows virus to reach cell surface
- Helps in the release of newly-formed mature Flu viruses from host cells
What does hemagglutinin (H) (type of Flu spike protein) do?
ATTACHES to receptors on respiratory tract epithelial cells
T or F: Either the neuraminidase OR the hemagglutinin of the influenza virus is enough for the virus to infiltrate host cells.
F
BOTH are needed
T or F: Both neuraminidase AND hemagglutinin are needed for the influenza virus to be released from the host cell.
F
Only neuraminidase is needed for the release of influenza viruses from the host cell.
Three types of influenza virus?
Type A
Type B
Type C
What is the most common type of influenza virus?
Type A
Which type of influenza causes the most severe symptoms?
Type A
What’s the most MILD type of influenza?
Type C
Which influenza type has H and N types?
Type A
If a patient is infected w/ H5N1, which type of influenza does he have?
Type A (only type A has H and N designations)
Which influenza type has a broad host range?
Type A
Which influenza type has a limited host range (humans and some marine mammals only)?
Type B
What is antigenic drifting?
When, during virus replication, random mutations occur in H or N genes, resulting in MINOR changes in H or N surface spike proteins.
What is antigenic shifting?
Two viruses with different subtypes infect the same host at the same time > H and N genes of flu’s SEGMENTED genome re-assort (mix) > progeny viruses are hybrids of the two original viruses (i.e. NEW SUBTYPE)
What’re the two ways flu viruses can evolve over time?
- Antigenic shifting
2. Antigenic drifting
Random mutations occurring in influenza’s genome is called…
a. antigenic drifting
b. antigenic shifting
a.
Genetic shuffling b/w the genomes of two influenza viruses is called…
a. antigenic drifting
b. antigenic shifting
b.
Different strains of influenza are brought about through…
a. antigenic drifting
b. antigenic shifting
a.
Different subtypes of influenza A are brought about by…
a. antigenic drifting
b. antigenic shifting
b.
Influenza A enters and replicates in which cells?
Epithelial cells of the upper and lower respiratory tract
What’s the incubation period of influenza A viruses?
1-3 days before onset of symptoms
How long before the onset of symptoms is one contagious with the flu virus? How long after the symptoms are gone?
1 day before symptoms
up to 5 days after symptoms
What is the major complication associated w/ influenza infections?
Secondary bacterial infections in the lungs
Do I have the flu or a cold?
I have a high fever.
Flu
Do I have the flu or a cold?
I have a headache.
Flu
Do I have the flu or a cold?
I don’t have any aches or pains.
Cold
Do I have the flu or a cold?
I have extreme fatigue
Flu
Do I have the flu or a cold?
I have a runny nose.
Can be either the flu or a cold.
Do I have the flu or a cold?
I have a sore throat.
Can be either the flu or a cold.
How is lab diagnosis of the influenza virus conducted?
Nasopharyngeal swab (far back into nasopharyngeal area) > Nucleic acid amplification test (PCR) performed for identification of viral nucleic acid
What is usually the treatment plan for a person suffering from an influenza infection? (4)
- Rest
- Fever-relief
- Nutrition
- Hydration
What’re two antivirals that’re used in exceptional circumstances to battle a flu infection? How do they work?
- oseltamivir
- zanamivir
They block neuraminidase activity of influenza type A only.
Oseltamivir and zanamivir reduce the risk of infection by the flu by ___%.
75%
Protective immunity against the flu is achieved when you have antibodies against THIS flu surface spike protein.
H protein (having N antibodies as well would be ideal, but not required for protective immunity)
What’s the problem with immunity against the flu?
Immunity is STRAIN-SPECIFIC
T or F: If you’re immune against H1N1, then you’re also protected against H3N2.
F
The flu vaccine contains either…(2)
- killed whole virus, or
2. H and N proteins
How effective is the flu vaccine at protecting against the flu?
50-60%
After getting the flu shot, how long before antibodies against the flu are fully developed?
~2 weeks
How long does a flu vaccination last?
~1 year
What’re 2 reasons the protection against the flu virus with the vaccine is only 50-60%?
- The flu virus may CHANGE (subtype/strain variations)
2. Diff pt pops respond differently to the vaccine
Why do inds need to get the flu vaccine each year?
- Antibodies from last year are mostly gone
2. New influenza strains in circulation that weren’t included in prev year’s vaccine fmlation
Name a virus responsible for a new, emerging viral disease.
Ebola virus
Structure of the ebola virus?
Enveloped RNA virus w/ a “pleomorphic” (i.e. inconsistent) morphology
Where is Ebola virus found naturally?
African continent
Ebola virus is an example of a “_____ _____ virus”
hemorrhagic fever
How is Ebola virus transmitted?
Blood or bodily fluids
Which blood cell type initially gets infected by Ebola virus?
White blood cells
How does Ebola virus spread throughout the body?
Lymphatic system
What’re three things that the Ebola virus does to the body?(3)
- Increases vascular permeability (thus, blood vessels leak)
- Interferes w/ coagulation system
- Dysregulation of the immune system
T or F: Ebola virus eventually causes multi-organ failure, leading to death.
T
How early can symptoms of Ebola infection show up after being infected? On avg, how many days does it take for symptoms to appear after infection?
As early as 2 days after being infected
Avg: 8 days after being infected
T or F: Ebola virus infections progress very slowly.
F
Pts worsen RAPIDLY after the onset of symptoms
What anti-virals can be used to treat Ebola virus?
None available; only supportive care is possible
What 5 things can be done in the supportive care of a person suffering from an Ebola virus infection?
- Maintain ELECTROLYTE balance
- Aggressive FLUID replacement
- Maintain BP and oxygenation
- Nutritional support
- Pain ctrl
What do we know about “emerging” diseases? (4)
- They usually start as “zoonotic” diseases
- International outbreaks = possible
- Outbreaks are sustained by human-human contact
- Recognizing and fighting “new” viral diseases = challenging
What type of microbe will likely cause an emerging infectious disease in the future?
a. bacteria
b. fungi
c. viruses
c. viruses
What three characteristics about a virus make it compatible w/ the def’n of something that is “alive”?
- Contain nucleic acids, proteins, and s.times lipids and enzymes
- They can “reproduce”
- Their genes mutate and evolve
What three characteristics about a virus make it incompatible w/ the def’n of something that is “alive”?
- No cellular organization
- Totally inert outside of host cell
- Replication is via self-assembly of pre-formed components
What’re 3 hypotheses regarding the origins of viruses?
- “Retrograde” evolution (cells continuously lost fns until they became completely dependent on another host)
- Cellular origin (combos of cellular macromolecules eventually gained the ability to self-assemble and replicate
- Parallel evolution w/ cells when life first began.
What microbe may be the “missing link” b/w the cellular and viral worlds?
Mimivirus (“mimicking microbe”)
How many genes does a mimivirus have?
~900 genes
What percent of human genetic material originates from viruses?
8%(!!)
