Card Set Information
Describe this figure
Model of viral infection w/ varicella-zoster (chicken pox)
The infection is initiated either in the conjunctiva of the eye or in the mucosa of the upper respiratory tract
moves quickly to regional lymph nodes, where it can infect T cells
4 to 6 days later, infected T cells move into the blood causing a primary viremia.
It moves to the liver, spleen and other organs, causing a second round of infection and then back into the blood causing secondary viremia (skin lesions appear)
moves into sensory ganglia in the peripheral nervous system, where it becomes latent
What is an acute infection?
Best understood infections and involve the rapid production of viron's followed by rapid resolution and elimination of the infection by host defenses
Some are asymptomatic
main problem is the incubation period; by the time they show symptoms the virus has already been transmitted. two examples
: common cold and influenza.
What is a latent infection?
Is known as a persistent infection (chronic infection is also persistent)
caused when host defenses are either modulated or completely bypassed
virions are produced for months or even years
Cytotoxic T cells (CD8+) are key in getting rid of these infections (adaptive immune response).
no large scale production of virions
reduced or absent immune response
persistence of an intact viral genome so infections can reoccur
can be re-actived years after entry into host
Explain slow infections
Lethal- associated usually w/ brain infections
Signs may not be seen until years after the primary infection
Once S/S appears (difficulties w/ brain function and motor skills), death usually follows very quickly
What is antigenic drift?
Involves small changes in viron structure Results from mutations
Occurs after infection has began
What is antigenic shift?
Major changes in viron structure
due to acquisition of new genes
this through co-infection or recombination
viruses cause significant disease
Define non-virulent, attenuated
At one point it was virulent, but now its not. They cause little or no disease.
What are the three types of vaccines?
Live attenuated vaccine
: made of intact virions rendered non-infectious
Inactivated or killed vaccine
: composed of killed or dead virions
: composed of immunogenic parts of virions
What are passive and active immunization?
: a performed antiviral product, such as antibody, is administered
: antigen is administered & causes the onset of the immune response
What are some methods to measure virulence?
LD50= how much virus is required to kill 50% of a subject population
ID50= how much virus is required to infect 50% of a subject population
PD50= how much virus is required to paralyze 50% of a subject population
produce virions and kill host cells rapidly (cytopathology)
produce virions but do not cause cytopathology
Spread of viruses in an infected body