32 - Viral Infections

Question 1

Should you treat a suspected viral meningitis with antibiotics?

Answer 1

always. they appear similar.

Question 2

What are CSF findings for bacterial meningitis?

Answer 2

low glucose
high protein, WBC and neutros
cloudy

Question 3

What are most common causes of viral meningitis?

Answer 3

enterovirus: echo, coxcacki, entero71
mumps
recurrent aseptic meningitsL HSV2, HIV, VZV

Question 4

Most common causes of viral encephalitis?

Answer 4

aborviruses: (via ticks/mosquits seasonally)
enteroviruses: family epidemics via URI/GI (oralfecal)
HSV-1 (temporal lobe)

Question 5

Which HSV is likely to cause encephalitis? Which one for menigitis?

Answer 5

HSV1 for encephalits

HSV2 for recurrent meningitis

Question 6

What opportunistic infections of the CNS are common with AIDS?

Answer 6

toxoplasmosis, crypto, TB JCV (PML), CMV

Question 7

What CNS neoplasms can arise with AIDS

Answer 7

primary CNS lymphoma or metastatic kaposi’s

Question 8

Characteristics of flaviviridae?

Answer 8

enveloped, nonsegmented, +RNA

Question 9

What are the 3 genera of flaviviridae we know?

Answer 9

flaviviruses: st louis, west nile, japanese encV
Pestivirus: cow, pig, sheep
HCV

Question 10

What is replication cycle for flaviviridae?

Answer 10

enter via receptor mediated endocytosis.
translation of +RNA by host ribosomes
single polyprotein cleaved by viral and host proteases
viral polymerase replicates genomic RNA
assembly of capsid and envelope
bud into ER/golgi and leave with envelope

Question 11

What is transmission of flaviviridae?

Answer 11

insect bites. Humans are not the primary host.

Question 12

What is clinical syndrome for st louis encephalitis?

Answer 12

cough, fever, ehadache sore throat
4 days later subacute meningeal/neuro signs
50% dead in the week, 80% dead in 2 weeks.
Most don’t progress to encephalitis though.

Question 13

What is course of west nile virus?

Answer 13

1% of bitten infected.
most are mild disease with fever, headache, muscle ache, rash and lymphadenopathy.
Some progress to meningitis symptoms with stuor and convulsions –> coma death

Question 14

Is there a vaccine for Japanse encepahlitis?

Answer 14

yes and travellors staying for longer than 1 month should get it in asia, india, soviet republic

Question 15

Characteristics of togaviridae?

Answer 15

enveloped, nonsegmented, RNA+ virus

Question 16

What are the two genera of togaviridae?

Answer 16

rubivuruses: rubella
alphaviruses: western, eastern, and venzuelan equine viruses

Question 17

What is replication cycle for togaviridae?

Answer 17

enter cell via receptor-endocytosis
RNA+recognized as mRNA and polymase trnaslated first.
RNA- made, and serves as template for genome and subgenomic polyproteins

Question 18

Clinical course of alpha virus?

Answer 18

most commonly asymptomatic, but can cause encephalitis.
alpha virus replicates in muscle/fibroblasts of many organs
2 weeks later, encephalitis and death few days later.

Question 19

What is preventative method for alpha viruses?

Answer 19

vaccinate horses and lab workers. No standard population vaccines.

Question 20

Characteristics of bunyaviridae?

Answer 20

enveloped, segmented, spherical negative ssRNA.

Question 21

What are two genera of bunyaviridae?

Answer 21

california encephalitis

lacross encephalitis

Question 22

Replication cycle of bunyaviridae?

Answer 22

similar to influenza except replication occurs in cytoplasm.

Question 23

Clincial course of lacrosse?

Answer 23

seizures with focal signs = low mortality

Question 24

What is most common cause of pediatric encaphlitis in US?

Answer 24

LaCrosse encephalitis virus

Question 25

Which virus types are transmitted by mosquito/tick?

Answer 25

flaviviridae: st, louis, west nile, japanese, HCV
togaviridae: rubiviruses, alphavirus
Bunyaviridae: california and lacrosse

Question 26

You isolate a bullet shaped, enveloped, nonsegmented, -RNA virus. What do you suspect?

Answer 26

vesiculovirus or lyssaviruses (rabies)

Question 27

What is post exposure prophylaxis for rabies?

Answer 27

wound cleanse, human rabies Ig at wound site, vaccination (works b/c of long incubation period)

Question 28

What is replication cycle for rhabdoviridae?

Answer 28

similar to paramyxovirus except enters by ph dependent post-endocytosis

Question 29

What is teh virus that causes rabies?

Answer 29

lyssavirus

Question 30

What are three phases of rabies?

Answer 30

prodromal: abnormal sensation around bite
acute neurologic - furious rabies or paralytic dumb with hydrophobia
coma - 7 days after acute neurologic phase. Death via respiratory arrest

Question 31

What is main cause of death in rabies?

Answer 31

respiratory arrest

Question 32

What are characteristics of arenaviridae?

Answer 32

enveloped, segmented, ambisense RNA virus with 2 RNA segments for 4 proteins.
Contains host cell ribosomes

Question 33

What virus belongs to arenaviridae?

Answer 33

lymphocytic choriomeiningitis (LCMV)

Question 34

reaplication scheme of LCMV?

Answer 34

entry via ph dependent post-endocyto
Ambisense strategy: genome used as template for transcription of NP + L mRNA from Long + short RNA

polymerase produces full length antigenome of segments

+sense antigenome used as template for gp mRNA
assembly of particles and release.

Question 35

how is LCMV transmitted?

Answer 35

inhalation of virus from rodent excreta/saliva

Question 36

Clinical course of LCMV?

Answer 36

rarely fatal
Initial pahse of prodrome fever, headache, n/v
aseptic meningitis 10 days later. Possible sudden deafness.

Question 37

treatment for LCMV?

Answer 37

supportive.

no vaccine