Lecture 4 Flashcards
True or false: most infections have no consequence and many infections are inapparent
true
why was the west nile virus infection so bad
-it spread in the USA in less than 4 years
-1 000 000 infections by oct 2004
-febrile illness developed in 20% neuro invasive 1%
-most people infected had no obvious disease=inability to stop the epidemic because it cannot be recognized early
What is pathogenesis?
The process of producing a disease
How does the virus enter the host? Host response? Where does replication occur? How does the infection spread? What tissues are infected? Acute or chronic? Transmission? etc.
What are the 2 effects of viral disease?
-effects of viral replication on the host
-effects of host response on the virus and host
True or false: effects of host response on the virus and host are not the ones that create symptoms
false usually they are the ones that will create symptoms like our body response to a bad virus will be to have fever and that is what we usually feel
What are the requirements of a successful infection?
-sufficient quantity of virus
-accessible, susceptible and permissive cells
-local antiviral response absent or overcome
what are good barries of our body against viruses?
skin
eyes thanks to tears
mucus
What is a susceptible cell?
A susceptible cell has a functional receptor for a given virus - the cell may or may not be able to support viral replication
if it is not able to support viral replication it might need smth else that is tissue specific
What is a resistant cell?
A resistant cell has no receptor - it may or may not be competent to support viral replication
even if the virus can’t enter the cell, if you introduce the virus in other ways like through an infectious cDNA or transfect the rna into the cell, it might support replication
What is a permissive cell?
A permissive cell has the capacity to replicate virus - it may or may not be susceptible
True or false: a susceptible and permissive cell is the only cell that can take up a virus particle and replicate it
true
What are the places where a virus can gain access
-skin
-mucosal surfaces
respiratory tract
alimentary tract
urogenital tract
-eye
-fetus (transplacental perinatal)
what is required to maintain the chain of infection?
spread from one susceptible host to another
what are the 2 general patterns for transmission of infection?
-Direct transmission (i.e. human-to-human)
-Vector-borne (i.e. mosquito-to-human)
What does isolation mean?
Isolation - separates sick people with a contagious disease from people who are not sick
What does quarantine mean?
Quarantine - separates and restricts the movement of people who were exposed to a contagious disease in case they become sick
These people may have been exposed to a disease, or they may have the disease but do not have symptoms
what does nosocomial mean and why us it so common
Nosocomial - when an individual is infected while in a hospital or health care facility
so common cuz we stick lots of sick people in there
what does iatrogenic mean?
Iatrogenic - activity of healthcare worker leads to infection
ex: reused needles
What does horizontal transmission mean?
Horizontal transmission - between members of the same species (zoonotic = different species to another species)
like animal to human
What does vertical transmission mean?
Vertical transmission - transfer of an infection between parent and offspring
what does germ line transmission mean?
Germ line transmission - transmitted as part of the genome (e.g. proviral DNA)
True or false: after replication at the site of entry, viruses all remain localized
falseeee
-After replication at the site of entry, viruses may remain localized but some might spread beyond the primary site aka disseminated like the dengue virus
-if many organs are infected = systemic
-physical and immune barriers must be breached
what is viremia?
presence of virus in blood
usually, you have the passive viremia wich is the inoculum, then the primary viremia which is the 1st replication at the source of origin, then the secondary viremia which is the secondary replication at the distal sites
what was the cause of lots of contaminated blood supplies in the 80s
Hep C because at that time we did not do some blood screenings before taking blood from donors
what is the viral spread of mousepox?
virus goes through lesion in skin then replicates in lymph nodes
-goes to the blood
-replicated in liver and spleen
-goes in the blood and shed on skin
=rash on skin
What is tissue tropism
-The spectrum of tissues infected by a virus
Enterotropic, neurotropic, hepatotropic, etc
-ranges from limited (like hep C which pretty much only infects the cells in liver) to pantropic (like polio which pretty much infects every cells)
What are the determinants of tissue tropism
Determinants: susceptibility (does the cell have the receptors), permissivity (can the cell support the replication), accessibility (which barriers have to be breached? like the BBB is stronggggg), host defenses, etc.