Viruses Flashcards
(35 cards)
Do viruses reproduce?
No, they use host cells to make copies of themselves
What are the proteins on the surface of viruses useful for?
They’re important for attaching to and entering cells
What are the 2 ways that viruses evolve?
- Antigenic Drift
- Antigenic Shift
How does antigenic drift work for viruses?
- When small changes in the virus occur gradually through the accumulation of mutations
- Viruses undergo slow or limited evolution
How does antigenic shift work for viruses?
- Viruses show rapid evolution when they infect a new host species
- Large abrupt changes that occur, often because cell has been infected by multiple viruses (from more than one species)
- When a shift happens, most people have little to no protection/immunity against the new virus
What contributes to our susceptibility to contracting Influenza year after year?
Antigenic drift
Because of what will seasonal flu change over the course of the year? What also causes the need for flu vaccines every year or 2?
Antigenic drift
What’s an epidemic?
An unexpected increase in the number of disease cases in a specific geographical area
What’s a pandemic?
An epidemic that spreads across countries and/or continents
What’s an endemic?
- When a disease is consistently present in a particular region. This makes the disease spread and disease rates predictable.
- We know how to deal with endemic (masks, social distancing)
What are the 2 forms of direct transmission?
- Person-to-person contact
- Droplet transmission
What’s person-to-person transmission?
Transmission that results from coming into contact with another person (or their bodily fluids)
Ex: HIV or Ebola
What’s droplet transmission?
When a host sneezes or coughs on another
Ex: Covid and Influenza
Larger droplets = respiratory droplets
Smaller droplets = droplet nuclei
What are the 3 forms of indirect transmission?
- Airborne transmission
- Vector Transmission
- Waterborne Transmission
What’s airborne transmission?
Droplet nuclei from evaporated droplets or dust particles containing bacteria or virus are suspended in the air and enter the respiratory system
Ex: tuberculosis, chickenpox
What’s vector transmission?
Getting picked up by a carrier (ex: a mosquito) and carried into a new host
Ex: malaria
What’s waterborne transmission?
Leaving one host and infecting the water supply and being taken up by a new host
Ex: cholera
What’s virulence?
How much the virus/bacteria affects the host’s fitness
What’s a way to think of virulence?
Think of it as the reproductive output of the virus/bacteria
More virulence means…
Less chance for transmission
Less virulence means…
More chance for transmission
What will the fitness of the virus/bacteria depend on?
How virulent and transmissible it is
Natural selection should favour viruses/bacteria that achieve a balance between what?
How severe the disease they cause is (virulence) and how easy it is for hosts to catch it (transmissibility)
The H1N1 Influenza virus is an example of an antigenic drift or shift?
Antigenic shift
