(Section A: Virology) Lecture 06: Viral Pathogenesis Flashcards
Why is skin not a good host?
Because it’s dead
* Not useful for virus replication
What are inapparent infections?
Infection occurs but there are no symptoms
What case study was used for the inapparent infection?
1999 West Nile Virus (WNV) in NYC
* 80% didn’t know they were infected (could transmit it through blood donations etc.)
What does a phylogenetic tree show?
Shows cluster genomes, similar/related genomes
What was the NYC-1999 WNV most related to?
Israel-1998 WNV
How was it discovered that mosquitoes can transmit disease?
Reed Commision (1901)
* Infected mosquitoes were brought to bite people
* People died = Infected with disease
Define:
Viral Pathogenesis
- Viruses spread to organs via bloodstream
- Virus spreads outside due to various methods (excretion etc.)
How does viral pathogenesis occur?
Cell must be permissive and susceptive
To produce a disease, what must happen?
- Effects of viral replication
- Effects of host response
Together, a disease occurs
Describe:
Fenner Experiment
- Injected mousepox into footpads of mouse
- 7-11 days after, the foot swells, rashes and ulcers appear on foot and surface of animal
Define:
Viremia
Presence of virions in the blood
Define:
Primary viremia
Progeny virions released in blood after initial replication at the site of entry
Define:
Secondary Viremia
Delayed appearance of virions in the blood, spread of virions from secondarily infected tissues
Describe:
Primary and secondary viremia in mousepox
Primary: Release of virions into lymph nodes
Secondary: Release of virions into bloodstream
List:
Entry points for viruses
- Conjunctiva
- Respiratory tract (muscosal lining)
- Alimentary tract (mucosal lining)
- Urogenital tract (mucosal lining)
- Skin
What qualities of skin make it a bad host for viruses?
- Acidic environment (5.0-5.5 pH)
- Anti-viral peptides are present
- Dry environment
How can viruses enter the body through the skin?
When the epidermis (outer layer) of skin is punctured, the dermis is exposed to infection by viruses
Describe:
Entry through Respiratory Tract
(use a virus as an example)
Virus enters via aerosolized droplets or through saliva
* E.x. Rhinoviruses (common cold), influenza
* The lung has 140 m^2 of area, giving viruses a chance of entering the body
* The body isn’t dumb, it has mucous to line linings to prevent infection
Describe:
Entry through alimentary tract
(Use 2 viruses for example)
Can go down with food
* E.x. Reoviruses (causes gastroenteritis)
Can enter through lower alimentary tract
* E.x. HIV
What must a virus be like in order to enter the body through the upper alimentary tract?
- Must be able to survive acidic environments and proteases
Why can’t HIV enter through upper alimentary tract?
HIV is an enveloped virus, it cannot survive the tough conditions
Why can reoviruses survive going through the upper alimentary tract?
They are like “onions”
* Many layers, helps keep them through the acidic environment and into the intestine before releasing genome
Describe:
Entry through urogenital pathway
(Use a virus as an example)
Usually occurs through sexual intercourse
* E.x. Retroviruses (HIV), Human papillomavirus (HPV)
What offers protection against viruses in the urogenital tract?
Mucus linings and the pH of the environment both offer protection
What viruses can enter through conjunctiva? What is a defense mechanism?
Adenoviruses
* Blinking is a mechanism to wipe away foreign objects and prevent infections in the eye
Define:
Virus Shedding
The release of virions from an infected individual
What are methods that viruses can shed through?
- Aerosol secretions (coughing, talking, sneezing)
- Feces
- Blood
- Milk
- Urine, semen
- Skin lesion
What viruses can be transmitted through skin lesions?
Herpes simplex
True or False:
Viral transmission has to occur in one species
False, it can be intra- or interspecies
What are qualities of non-enveloped viruses that methods that they are transmitted through?
- Hardy
- Transmitted through repiratory and alimentary methods
- Transmitted through fomites
Define:
Fomite
Objects contaminated with viruses
What are qualities of enveloped viruses that make them hard to transmit? What methods can they transmit?
- Fragile
- Sensitive to low pH
- Mostly transmitted through aerosol transmission
List:
Modes of Transmission
- Iatrogenic
- Nosocomial
- Vertical
- Germline
- Horizontal
Define:
Iatrogenic transmission
Transmitted by healthcare worker, direct contact (eg. after a surgery)
Define:
Nosocomial transmission
Transmitted in a hospital setting, not necessarily through direct contact
Define:
Vertical transmission
Transmitted from parent to offspring
Define:
Germline transmission
Transmitted through genetics (genomic transfer)
Define:
Horizontal Transmission
Transmitted in the same species (not any above the previous mentioned scenarios)
Describe:
The case study that Dr. Dikeakos showed about transmission
Puglia, Italy
* Celebrates a holiday by eating raw shellfish
* Fishers poop in the water during long fishing trips
* Fishers are infected with hepatovirus (hepatitis A), transmitted to shellfish
* Transmitted to customers purchasing shellfish
