Viral Pathogenesis Flashcards
1
Q
How do viruses make us sick
A
- how do viruses get into our bodies
- why are viral infections so miserable
- how exactly do viruses damage the host
- what do we know about how viruses cause disease
2
Q
where do we encounter viruses
A
- people
- animals
- insects
- food and water
3
Q
mechanisms of viral transmission
A
- respiratory: aerosols
- fecal-oral: food, water, dirty hands
- contact- lesions, saliva, fomites
- zoonoses- animals, insects
- blood- direct contact, blood products, organ transplants
- sexual- mucous membranes, blood
- maternal-neonatal- birth, breastmilk
- genetic- prions, retroviruses
4
Q
Susceptibility and severity of viral disease depend on
A
- the nature of exposure- route- aerosol vs scratch
- the viral dose- more virions increases risk of disease
- the status of person- age, general health, immune status
- the virus-host interactions- unique genetic features of each
5
Q
Routes of entry, disemination and shedding in host example: smallpox
A
-acquired through respiratory tract, disseminates in blood and sheds from postules on the skin
6
Q
Virus sites of enry
A
- in and out of conjunctiva
- in and out of respiratory tract
- in of alimentary tract
- in and out of urinogenital tract and anus
- scratch injury
- arthropod (bug)
- capillary
7
Q
Sites of virus entry in the respiratory host
A
- turbinate baffles
- tonsillar lymphoid tissues
- cervical lymph node
- esophagus
- trachea
- bronchi
- bronchioles
- bronchial lymph node
- alveolus
8
Q
Virus entry into M cells in GI tract
A
- M cell sample the gut contents and present it to underlying immune cells
- viruses can infect M cells and easily reach the blood stream
- Reovirus attach to M cells
9
Q
Virus Dissemination
A
- virus may spread from the surface of the body to lymph nodes and the blood stream
- primary viremia leads to
- replication in internal organs
- may occur without symptoms (incubation stage)
- secondary viremia disseminates the virus to organs where it is shed
- transmission may be by direct contact or through the environment (air, water, objects)
- exposure to infected blood is now a common route of transmission
10
Q
Excretion of HIV-1
A
- HIV was measured by PCR
- most virus was in blood plasma and lymphocytes and in CSF
- sperm had less virus than semen
- in ear wax- weird
11
Q
Virus Host interactions
A
- virus infection may be unnoticed, cause illness, induce autoimmunity, be persistent, or be lethal
- a successful virus will avoid destruction by the immune system and avoid destroying the host before replication is finished
12
Q
General patterns of infection
A
- acute- common cold
- persistent
- latent-varicella-zoster
- slow
- transforming
13
Q
Injury induced by viruses
A
- symptoms of viral disease (fever, tissue damage, rash, aches, pains, nausea) are mainly caused by the host response to infection
- virus replication -> cell injury <-host response
- cell injury is caused directly by viruses and indirectly by the host
- direct effects: cell lysis
14
Q
Direct effect of virus: cell inactivation
A
- virus infection may halt essential cell functions
- infected cells are susceptible to apoptosis
- loss of cell functions can lead to organ damage or failure
15
Q
Indirect effects of immunopathology
A
- the host immune response to a virus may be the sole cause of disease
- immune pathology usually caused by T cells and antibody complexes
- caution: vaccination can make some viral infections worse
- corneal scarring caused by immune response to chronic HSV reactivation
