microbiology- how viruses cause disease

Question 1

describe viruses

Answer 1

simple micro-organisms
not capable of independent existence
require host cell

Question 2

describe the basic viral structure

Answer 2

dna/rna located in the capsid protein

lipoprotein envelope which protein molecules attached

Question 3

how are viruses classified

Answer 3

1. type of nucleic acid

2. presence/absence of an envelope

Question 4

what are the steps of the virus life cycle

Answer 4

1.attachment 
2 entry 
3. replication
4 assembly 
5 release

Question 5

describe how the virus attaches

Answer 5

it enters the body by inhalation, ingestion or injection and then collides with the host cell

Question 6

define viral tropism

Answer 6

this is what determines if the virus can enter and attach by binding to a specific receptor

Question 7

how does the cell life cycle continues

Answer 7

cells be permissive

Question 8

what does permissive mean

Answer 8

contain the whole range of components required by the virus for replication to be completed

Question 9

what are the three types of tropism

Answer 9

cellular
tissue
host

Question 10

describe entry

Answer 10

immediately follows attachment

Question 11

how do enveloped viruses enter

Answer 11

enter by membrane fusion or endocytosis

Question 12

how do non enveloped viruses enter

Answer 12

entry by endocytosis or penetration( direct injection)

Question 13

describe the stages of entry

Answer 13

membrane fusion

1. occurs by receptor binding
2. the virus fuses with the host membrane
3. release of virion content into the host cytoplasm

Question 14

how does replication occur

Answer 14

once inside the cell the virus removes its capsid and exposes its genome- the uncoating is specific to the virus

Question 15

what types of uncoating do we have

Answer 15

nuclear or cytoplasmic

Question 16

what are the stages of replication

Answer 16

viruses hijack the replication process in cells by creating and injecting their own viral MRNA
using host cell machinery to make viral proteins instead of host proteins
new virons are constructed from viral proteins

Question 17

describe assembly

Answer 17

All viruses components are transported to a site of assembly and put together
• influenza virus proteins and new RNA are assembled at
the cell membrane, which then forms a “bud”

Question 18

describe release

Answer 18

by
lysis:
cell splits apart and dies
exocytosis: host cell transports the visions and release at surface
budding: visions enclose themselves in a host membrane

Question 19

what are the major mechanisms by how viruses cause disease

Answer 19

route of infection 
mucosal contact 
injection 
respiratory droplet 
faecal oral
direct contact

Question 20

to establish effective entry what does their need to be

Answer 20

enough virus
host cells which are accessible susceptible permissive
also the host immune system needs to be inadequate or absent

Question 21

what do localised infections look like

Answer 21

typically shorter incubation period
virus remains at the site of entry
may form focal lesions
may affect large areas of the same mucous membrane

Question 22

what do generalised/disseminated infections look like

Answer 22

longer inc time 
initial replication phase NEAR site of entry
then general spread 
to lymph nodes 
via nerves etc

Question 23

target organs which viruses can affect

Answer 23

skin rashes
respiratory tract
liver
central nervous system

Question 24

describe chronic illness duration

Answer 24

▪ Infection persists for a long period of time
▪ Host immune system is unable to fully control virus
▪ Ongoing viral replication alongside immune response progressively damages host cells over time

Question 25

describe illness duration in the latency phase

Answer 25

WHERE THE VIRUS INFECTS cells but does not replicate

Question 26

where does the herpes simplex virus and varicella zoster discover latency

Answer 26

in the dorsal root ganglion of the trigeminal nerve

Question 27

what does it mean when a virus transforms

Answer 27

Some viruses have the potential to induce malignant change by disruption the normal expression of the host cell genes

Question 28

what can epstein barr virus be associated with

Answer 28

Burkitts lymphoma

Question 29

what are the clinical stages of virus infection

Answer 29

incubation period
prodromal period
specific illness period
recovery period

Question 30

describe incubation period

Answer 30

the virus is attaching and undergoing the non productive stage of life cycle

Question 31

describe prodromal period

Answer 31

Non specific manifestations such as general body ache, malaise, fever
Early host immune response

Question 32

describe specific illness period

Answer 32

Specific effects of virus on the target cells

Host immune systems immunologic attack

Question 33

how can we reduce the effect of viruses

Answer 33

by using antivirals that attack and effect different cycles of the viruses life cycle
usually by targeting more than one stage

Question 34

which medications can block viral attachment and entry

Answer 34

enfuvirtide

maraviroc

Question 35

give examples of medications that block uncoating

Answer 35

amatadine

rimantadine

Question 36

give examples of medications that block nucleic acid synthesis

Answer 36

NRTIS

acyclovir

Question 37

give examples of medications that block late protein synthesis and processing

Answer 37

blocked by protease inhibitors

Question 38

the importance of viruses in dentistry

Answer 38

respiratory transmission 
COVID 19 
percutaneous injuries and blood splashes 
HBV 
skin to mouth
herpetic whitlow

Question 39

give examples of medications that block penetration

Answer 39

interferon alfa

Question 40

give examples of medications that block viral release

Answer 40

neuraminidase inhibitors