Lec 4: Transmission Flashcards
if the virus does not produce enough visions it will
die out
another possibility for viral survival…
which are…
to be maintained in cells as nucleic acids
which are replicated and passed on to daughter cells when they divide
Viruses of bacteria and other microbial hosts are…
…released from infected cells into the environment
- dependent upon chance encounters with susceptible cells.
Viruses of multicellular animals and plants — may…
…spread to adjacent cells, or to cells in a distant part of the host.
Some virus infections modify the…
& ex:
…behaviour of their hosts in order to increase the probability of transmission.
& ex: Mammals infected with rabies virus often become aggressive or rabid.
some viruses can be transmitted to new hosts without…
…seeing the light of day , (without exposure to the outside environment) — transmitted by kissing, sex, birth, vectors, etc.
Classical route of journey between hosts:
Cell free virions bind to permissive host cell with receptor-ligand interactions, followed by fusion to enter the cytoplasm and then replicative events.
Cell to cell transmission:
An actively infected cell can directly infect a second cell, without requirement for releasing cell-free virions into the local environment.
Why is cell to cell transmission advantageous? (2)
- Bypasses the need for virus diffusion into the local enviroment.
- Minimizes exposure to harsh environment, and viral neutralization defenses such as antibodies and complement.
some viruses travel ____ _________, through: (3)
long distances, through:
- ) bird migration
- ) human travel
- ) animal export
In a multicellular organism, viruses must survive…
In theory,…
…host defense mechanisms before suitable host cells are encountered.
…a single virion can initiate an infection, but in practice a host must be inoculated with a minimum number of virions in order for that host to become infected.
most vectors are
and sometimes referred to as
arthropods
“arboviruses”
Some viruses replicate in…
- There are viruses that can…
…one or more tissues and organs of their vectors.
- …replicate in both invertebrates and plants, and viruses that can replicate in both invertebrates and vertebrates.
Many (but not all) of the invertebrates suffer…
little or no harm when they are infected.
It’s possible that many of the modern plant viruses and vertebrate viruses are descended from…
…viruses of invertebrates that later extended their host ranges to plants or vertebrates.