MCM 2-24 Viral Pathogenesis

Question 1

difference between +ssRNA and mRNA

Answer 1

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

Question 2

fomites

Answer 2

inanimate objects that have pathogens on them (counters, handles)

Question 3

susceptibility and severity of viral disease depends on

Answer 3

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

Question 4

two viruses that can enter the body through a scratch

Answer 4

HSV1/2 and HPV

Question 5

describe the epithelial anatomy of the respiratory tract

Answer 5

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

Question 6

What do M-cells do? How are they effected by some viruses?

Answer 6

M-cells sample the gut contents and present to underlying immune cells.

Some viruses can infect M-cells and easily reach the blood stream.

Question 7

describe the common features of Reo and Roto-virus

Answer 7

both unenveloped, get sampled by M-cell and can make it across into the blood stream quickly.

Question 8

Rotovirus

transmission route
Virulence factor?
Immunity is mediated by?
important features?
Types?

Answer 8

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

Question 9

what is “dissemination” of a virus?

Answer 9

when the virus crosses the basement membrane of the body

Question 10

describe primary viremia

Answer 10

“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.

Question 11

any virus that interacts with the respiratory or gut epithelium requires

Answer 11

attatchment and receptor engagement

recognition and attachment

Question 12

What is secondary Viremia?

Answer 12

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

Question 13

describe chicken pox

Answer 13

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

Question 14

where are the highest levels of HIV found an in infected person?

Answer 14

blood plasma, lymphocytes, CSF, ear secretions

Question 15

virus infection may be…(5)

Answer 15

unnotticed, cause illness, induce autoimmunity, be persistent, or be lethal

Question 16

a successful virus will..

Answer 16

avoid destruction by the immune system and avoid destroying the host before replication is complete

Question 17

Persistent Vs Latent

Answer 17

Persistent - you are able to culture virus in the absense of disease

latent - cannot culture virus in absence of disease

acute - virus goes away

Question 18

5 patterns of viral infection

Answer 18

Acute, Chronic (persistent, latent, slow), transforming

Question 19

infection pattern of

common cold

measles, SSPE

varicella-zoster

hep-B

HIV

Creutzfeld-Jacob

Answer 19

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

Question 20

Symptoms of viral disease includes

Answer 20

fever, tissue damage, rash, aches, pains, nausea = mainly caused by the HOST response to infection (mainly interleuken)

Question 21

cell injury is caused by

Answer 21

directly by viruses, indirectly by host reaction

Question 22

Norwalk Virus

transmission
Distribution
At risk
vaccine/treatment
prevention

Answer 22

fecal oral form contaminated water/food

no seasonal incidence

children, schools, resorts, cruise ships

no vaccines

treat with hydration

prevention = handwashing

Question 23

Describe synctium

Answer 23

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)

Question 24

Immunopathology

Answer 24

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

Question 25

common routes of viral entry

Answer 25

mainy viruses enter through facial passageways including conjunctiva (eye membrane), mouth, and mucous membranes.

Question 26

in the respiratory tract, viruses attatch to the...

Answer 26

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

Question 27

dissemination

Answer 27

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

Question 28

secondary viremia

Answer 28

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.

Question 29

transmission

Answer 29

After secondary viremia, the virus may be transmitted by direct contact, the environment, or the blood.

Question 30

Acute

Answer 30

Phases of virus amplification, disease episode, shedding period, and total clearance of the virus.

Question 31

Chronic

Answer 31

After the disease episode the virus remains in the host. Chronic infections are further subdivided.

Question 32

Chronic: Persistent

Answer 32

Persistent – After the amplification, disease, and shedding periods, the virus remains in the individual at detectable levels.

Question 33

Chronic: Latent –

Answer 33

After the amplification, disease, and shedding periods, no detectable amount of virus is present; then a recurrent disease emerges.

Question 34

Chronic: Slow

Answer 34

Chronic: Slow – Very long buildup of virus amplification leading up to the disease episode.

Question 35

transforming

Answer 35

viruses transform cells and can cause cancer

Question 36

what type of effect (direct or indirect) is cell lysis?

Answer 36

Cell Lysis – A direct effect. Killing of infected cells by lysis.

Question 37

What is DIFFERENT between rota-, noro-, and enteroviruses?

Answer 37

Rota and noroviruses stay in gut while enteroviruses have secondary replication outside the gut Enteroviruses can rarely invade the CNS

Question 38

What is the SAME among rota-, noro-, and enteroviruses?

Answer 38

All replicate in the gut All have RNA genomes All can fecal-oral transmit

Question 39

differences between Rotavirus and Norovirus

Answer 39

norovirus - nausea more common and severe (Cruiseship), but dehydration less likely than with rotavirus (diarreah)

Question 40

What is the most serious symptom of rotavirus infection and how is it treated?

Answer 40

Dehydration, supportive care

Question 41

What is an emerging disease? how to prevent spread?

Answer 41

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

Question 42

Infectious diseases are important to control because they have epidemic potential and can impact

Answer 42

healthcare/human suffering economics political stability regional security

Question 43

what are some reasons why viral genetic diversity occurs?

Answer 43

· Mutations · Recombination events · Reassortment · Natural Selection

Question 44

what are some factors that allow diseases to emerge?

Answer 44

International travel Human behavior War/Famine Breakdown is public health measures