MCM 2-24 Viral Pathogenesis Flashcards
difference between +ssRNA and mRNA
sometimes they are the same. mRNA needs cap and poly-A tail to be recognized by a ribosome
sometimes a +RNA must get changed to -RNA first by RDRP, then trascribed into mRNA for the ribosomes
fomites
inanimate objects that have pathogens on them (counters, handles)
susceptibility and severity of viral disease depends on
if it is the correct
exposure route
dose
the status of the person
virus-host interaction - unique genetic features of the person and that viral strain
two viruses that can enter the body through a scratch
HSV1/2 and HPV
describe the epithelial anatomy of the respiratory tract
covered in mucus, ciliated cells and goblet cells with basement membrane (barrier to some viruses). Polarized - the apical is unlike the basal
some viruses enter/leave through the apical (flu)
other enter apical and can pass through the basal membrane
What do M-cells do? How are they effected by some viruses?
M-cells sample the gut contents and present to underlying immune cells.
Some viruses can infect M-cells and easily reach the blood stream.
describe the common features of Reo and Roto-virus
both unenveloped, get sampled by M-cell and can make it across into the blood stream quickly.
Rotovirus
transmission route Virulence factor? Immunity is mediated by? important features? Types?
tranmission is fecal oral
virulence - nonstructure protein 4 (toxin) nsp4 - effects enterocytes causing massive diarreah
immunity is mediated by IgA by prior exposure OR oral vaccine
Important features - there is a vaccine, this is not a summer disease, very little dissemination - “straight shot through”
type a - under 2 years
type b - over 2 years
what is “dissemination” of a virus?
when the virus crosses the basement membrane of the body
describe primary viremia
“viruses may spread form the surface of the body to lymph nodes and blood stream”
“primary viremia leads to replication in internal organs, may occur without symptoms (incubation stage)
first appearance of virions in blood. May not be replicationg, but ability to detect virus in blood at low levels.
any virus that interacts with the respiratory or gut epithelium requires
attatchment and receptor engagement
recognition and attachment
What is secondary Viremia?
the virus disseminates to the virus to organs where it is shed
- trasmission may be by direct contact or through environment
- exposure to infected blood is now a common route of transmission
describe chicken pox
very contagious via respiratory and eyes
replicates in upper airway, travels to lymph nodes and infects T-cells to spread throughout body
- maintained in dorsal root ganglia for life
- virus always detectable in the blood
vaccines for zoster and varicella, some antivrials but they are not very effective
where are the highest levels of HIV found an in infected person?
blood plasma, lymphocytes, CSF, ear secretions
virus infection may be…(5)
unnotticed, 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 complete
Persistent Vs Latent
Persistent - you are able to culture virus in the absense of disease
latent - cannot culture virus in absence of disease
acute - virus goes away
5 patterns of viral infection
Acute, Chronic (persistent, latent, slow), transforming
infection pattern of
common cold
measles, SSPE
varicella-zoster
hep-B
HIV
Creutzfeld-Jacob
cold = acute
measles = acute infection with rare late complications
zoster - latent
hep-b = chronic with early disease episode
HIV=chronic infection with late disease episode, different acute episode
slow infection - general increase to a disease episode
Symptoms of viral disease includes
fever, tissue damage, rash, aches, pains, nausea = mainly caused by the HOST response to infection (mainly interleuken)
cell injury is caused by
directly by viruses, indirectly by host reaction
Norwalk Virus
transmission Distribution At risk vaccine/treatment prevention
fecal oral form contaminated water/food
no seasonal incidence
children, schools, resorts, cruise ships
no vaccines
treat with hydration
prevention = handwashing
Describe synctium
A direct effect causing cell damage induced by virus
cell inactivation by a virus causing cells to fuse together and lose function
infected cells susceptible to apoptosis
caused by RSV in respiratory tract (Respiratory Syncytial Virus)
Immunopathology
Indirect response, Host immune response to virus may cause the disease/injury
- ussually caused by T-cells and immune complexes
- May be made worse with vaccination
ex) herpes stromal keratitis - cause by effect of t-cell intervention of a frequent herpes reactivation in the eye
common routes of viral entry
mainy viruses enter through facial passageways including conjunctiva (eye membrane), mouth, and mucous membranes.
in the respiratory tract, viruses attatch to the…
mucous layer, from there they interact with the ciliated epithelial cells of the brush border and remain there to either
replicate
cross the basement membrane and penetrate the lymph and blood systems
dissemination
Viruses may spread from the surface of the body to lymph nodes via an immune cell. From there, it can reach the bloodstream for the first time. This is referred to as primary viremia (first appearance of virus in the blood…usually at a very low level
secondary viremia
fter replication in internal organs occurs, the virus can reenter the bloodstream (secondary viremia). During secondary viremia, the level of circulating virus is much higher, and symptoms usually emerge (end of incubation phase). From secondary viremia, the virus disseminates to the organs where it is shed.
transmission
After secondary viremia, the virus may be transmitted by direct contact, the environment, or the blood.
Acute
Phases of virus amplification, disease episode, shedding period, and total clearance of the virus.
Chronic
After the disease episode the virus remains in the host. Chronic infections are further subdivided.
Chronic: Persistent
Persistent – After the amplification, disease, and shedding periods, the virus remains in the individual at detectable levels.
Chronic: Latent –
After the amplification, disease, and shedding periods, no detectable amount of virus is present; then a recurrent disease emerges.
Chronic: Slow
Chronic: Slow – Very long buildup of virus amplification leading up to the disease episode.
transforming
viruses transform cells and can cause cancer
what type of effect (direct or indirect) is cell lysis?
Cell Lysis – A direct effect. Killing of infected cells by lysis.
What is DIFFERENT between rota-, noro-, and enteroviruses?
Rota and noroviruses stay in gut while enteroviruses have secondary replication outside the gut
Enteroviruses can rarely invade the CNS
What is the SAME among rota-, noro-, and enteroviruses?
All replicate in the gut
All have RNA genomes
All can fecal-oral transmit
differences between Rotavirus and Norovirus
norovirus - nausea more common and severe (Cruiseship), but dehydration less likely than with rotavirus (diarreah)
What is the most serious symptom of rotavirus infection and how is it treated?
Dehydration, supportive care
What is an emerging disease?
how to prevent spread?
emerging disease - infectious agens that have increased prevalence or threaten to do so due to biological/ecological factors
early detection and intervention is important to prevent spread/pandemic
Infectious diseases are important to control because they have epidemic potential and can impact
healthcare/human suffering
economics
political stability
regional security
what are some reasons why viral genetic diversity occurs?
· Mutations
· Recombination events
· Reassortment
· Natural Selection
what are some factors that allow diseases to emerge?
International travel
Human behavior
War/Famine
Breakdown is public health measures
