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Neuro Block 2 > CNS Viral Infections > Flashcards

CNS Viral Infections Flashcards

0
Q

What type of meningitis is most common overall?

A

Viral is more common, but bacterial can be deadly, so important to distinquish

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1
Q

In how many days does a viral meningitis usually resolve?

A

7-10 days

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2
Q

What types of virus cause 80% of viral meningitis?

A

Enterovirus–> Echo, Coxsackie, Enterovirus 71

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3
Q

What virus is responsible for recurrent aseptic meningitis usually?

A

Herpes simplex virus-2 (HIV or VZV also can cause)

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4
Q

What are 5 symptoms of viral meningitis?

A
  1. Fever
  2. Malaise
  3. Headache
  4. Stiff neck
  5. Low back pain (usually overshadowed by headache)
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5
Q

What disease can cause viral meningitis due to not being vaccinated?

A

Mumps

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6
Q

What category of viruses cause 30% of viral encephalitis?

A

Arborviruses–> these are transmitted by a zoonotic vector, usually mosquitos or ticks, so have a strong seasonality

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7
Q

What type of viruses cause viral encephalitis and may cause mini-epidemics within families?

A

Enteroviruses (echo, coxsackie, enterovirus 71)

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8
Q

What virus causes a little over a quarter of cases of viral encephalitis and may be fatal if not treated?

A

Herpes Simplex virus-1–> tx with acyclovir

*70% mortality w/o tx = DO NOT MISS

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9
Q

What part of the brain is preferentially affected by herpes viral encephalitis?

A

Temporal lobe–> causes hemorrhagic necrosis; can be visualized via MRI

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10
Q

What causes HSV encephalitis generally (mode of infection)?

A

More often due to reactivation of latent virus than by initial acute infection

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11
Q

Other than MRI findings, what finding can be suggestive of Herpes encephalitis?

A

RBCs in the CSF

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12
Q

Definitive test for dx of HSV encephalitis?

A

PCR (false negatives do occur though)

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13
Q

Flaviviridiae cause what three human diseases?

A
  1. St. Louis encephalitis
  2. West Nile
  3. Japanese encephalitis
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14
Q

Flaviviridiae are small, ________, _________, ___ strand ____ viruses

A

Enveloped, nonsegmented, (+) RNA viruses

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15
Q

Flaviviridiae have their RNA translated by host ribosomes into a single polyprotein.. what are the fragments cleaved by host proteases called? Fragments cleaved by viral proteases?

A

Host protease–> trans

Viral–> cis

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16
Q

Where do flaviviridiae first replicate in the host? After the transient primary viremia where do they travel to and replicate?

A

Initially replicate in the endothelium or epithelial cells surrounding the bite site, then after primary viremia replicate in spleen, lymph nodes and macrophages (occurs 3-7 days post exposure)

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17
Q

How do Flaviviridiae end up causing encephalitis?

A

If the infection is not controlled by the immune system following the primary viremia, then a secondary viremia occurs and results in the severe systemic disease (encephalitis)

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18
Q

What three clinical syndromes can occur with St. Louis encephalitis?

A
  1. Febrile headache
  2. Aseptic meningitis
  3. Encephalitis

*in 80s and 90s outbreaks have occurred in Colorado, California, Texas, Florida, and Arkansas

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19
Q

After initial onset of symptom in St. Louis encephalitis including malaise, fever, headache, sore throat or cough, what symptoms can occur in 1-4 days indicating severe disease?

A

acute or subacute meningeal and neurological signs

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20
Q

What is treatment for SLE?

A

None.. there are no vaccines and antiviral therapy has not been evaluated. Mosquito control is the best means of control

*Fatality rate is low, but those that have fatal infections usually die within 1-2 weeks

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21
Q

How does the West Nile virus get into mosquitoes?

A

Mosquitoes get from feeding on birds, the virus then replicates in the salivary glands of the mosquito

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22
Q

Most infections with West Nile virus usually only have what 4 symptoms?

A
  1. febrile headache
  2. myalgia
  3. skin rash
  4. swollen lymph nodes
    * only 1% will develop serious systemic disease
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23
Q

What symptoms are seen in patients that get severely ill from West Nile?

A
  1. Severe headache with high fever
  2. Neck stiffness, muscle weakness
  3. Stupor, disorientation, convulsions, tremors
  4. Coma, paralysis, and rarely, death
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24
Q

What is treatment for severe cases of West Nile?

A

Mainly supportive (I.V. fluids, respiratory support if needed)

25
Q

Travelers should get vaccinated against Japanese encephalitis virus if traveling to what four parts of the world for over 1 month?

A
  1. Asia
  2. SE Asia
  3. India
  4. Eastern portions of former Soviet Russia
26
Q

What 3 viruses of the Togaviridiae family can cause encephalitis?

A

Western, Eastern, and Venezuelan Equine viruses–> are called alphaviruses

(Same family that has Rubella-causing viruses, Rubavirus)

27
Q

Togaviridiae are ________, ________, __NA (_) viruses

A

Enveloped, non-segmented, RNA (+) viruses

28
Q

What is the first product translated by host polymerases in Togaviridiae replication?

A

viral polymerase–> then translates the +RNA to -RNA, which serves as a template for genomic and subgenomic polyproteins

29
Q

Where do Western, Eastern and Venezuelan Equine virues replicate initially in the host?

A

In muscle and fibroblasts

30
Q

Within 24 hours what does the primary viremia allow in EEV, WE viruses?

A

Allows for invasion of the CNS, with destruction of neurons

31
Q

What symptom is seen for ~ 2 weeks foolowing EEV and WEV, then what suddenly follows?

A

Fever for ~2 weeks, then abrupt onset of encephalitis

*Infection can range from asymptomatic to non-specific febrile illness to the devastating encephalitis–> depends on age of the patient and the dose of virus received during inoculum

32
Q

Once encephalitis sets in due to EEV/WEV/VEV what symptoms begin to develop? Outcome?

A

Dizziness and increasing loss of conciousness–> pts eventually become comatose and may die within the first few days of hospitilization. Incidence is quite low however

33
Q

Which Bunyaviridiae virrus is the moss common cause of arboviral-induced pediatric encephalitis in the US?

A

LaCross encephalitis virus–> produces seizures and focal neurological signs in childen, but have a low mortality rate and rare sequlae

34
Q

Bunyaviridiae are _______, ________, ____-strand, (_) __NA viruses

A

Enveloped, segmented, single-strand (-) RNA viruses

*are spherical

35
Q

Other than LaCross virus, what other Bunyavirus can cause encephalitis?

A

California encephalitis virus

36
Q

Rabies viruses are ________, ________ (_) __NA viruses

A

enveloped, non-segmented, (-) strand RNA viruses

*are probably he most widely distributed viruses known

37
Q

What characteristic morphological shape do Rabies viruses have?

A

“bullet-shaped” morphology

38
Q

Which particular Rhabdovirus is the causative agent of rabies?

A

Lyssavirus

39
Q

How do Rhabdoviruses enter the host cell?

A

In a pH-dependent fashion following endocytosis (single glycoprotein with pH-dependent fusion activity)

40
Q

Why does lyssavirus (rabies) affect the CNS?

A

Has a specific neurotropism for neural cells, so replication is restricted exclusively to neuronal cells

*after it reaches the brain it may spread to other organs

41
Q

What is the primary mechanism of spread for rabies virus (lyssavirus)?

A

Is found in high concentrations in salivary glands, so is spread by bites, licking, inhalation of aerosols

42
Q

How does lyssavirus reach the CNS?

A

Floowing the bite, virus enters muscles, where it replicates locally and is transported through peripheral sensory nerves to the spinal ganglia–> travels up the spinal cord to the brain

43
Q

What three places in the brain does lyssavirus like to hang out?

A
  1. Limbic system
  2. Midbrain
  3. Hypothalamus

*Basal parts of brain

44
Q

How does lyssavirus get into salivary glands?

A

Via efferent nerves to the submaxillary salivary glands (then replicates in high concentrations)

45
Q

How long (range) is the incubation period for lyssavirus? What determines how long or short it is?

A

1 week- 1 to 2 months

Depends on bite site and its proximity to the CNS

46
Q

What is a specific early symptom of rabies in the prodromal period that usually lasts 2-10 days following bite/exposure?

A

Abnormal sensations (itching, burning, numbness) around the bite site

47
Q

What marks the beginning of the Acute neurological phase of rabies (stage 2)? What causes “hydrophobia”?

A

Nervous system dysfunction–> anxienty, agitation, paralysis, episodes of delirium

*hydrophobia caused by an exaggerated gag reflex (hypereflexia)

48
Q

What usually occurs 2 - 7 days following the acute neurological phase in Rabies? How does death usually occur?

A

Coma (may last 3-30 days)

*Death typically follows from resulting respiratory arrest

49
Q

What is treatment for Rabies? (3 things)

A
  1. Wash wound thoroughly
  2. Admin of human anti-rabies Ig to wound
  3. Multiple doses of rabies vaccine (to the thigh or deltoid)

*vaccination is effective due to the long incubation period of the virus

50
Q

What is the most common vector of rabies in the US?

A

Skunk

*also foxes and raccoons; sometimes they put out bait with recombinant G protein to try to immunize the vectors

51
Q

What kind of vaccines are Rabies vaccines?

A

inactivated vaccines produced in cell culture

52
Q

What is the areniviridiae virus that can cause encephalitis?

A

Lymphocytic choriomeningitis virus (LCMV)

53
Q

LCMV are _______, _______ _NA viruses

A

enveloped, segmented RNA viruses

*contain 2 RNA segments encoding 4 proteins

54
Q

What do LCMV virions often contain that is unique?

A

Host cell ribosomes (arena is from arenosus, meaning “sandy”)

55
Q

Uncoating, transcription, and replication of LCMV occurs by an uncoventional _________ strategy

A

ambisense

56
Q

What does “ambisense” mean?

A

RNA segments encode several proteins and are read in both directions to produce more proteins than usual

57
Q

What does the L strand of LCMV encode?

A

The virus’ RNA-dependent RNA polymerase (needed to make the (-) strands originally contained in the virus into (+) sense

58
Q

What does the S strand of LCMV RNA encode?

A

Structural proteins

59
Q

What is the reservoir for LCMV, in contrast to most others discuused here?

A

Rodents, including hamsters and mice

*can infect people working in labs or those inhaling feces dropped by house mice

60
Q

The initial phase of LCMV infections usually involves what symptoms?

A

Fever, headache, N/V–> these coincide with the viremia

61
Q

After about 10 days following the initial symptoms, what can follow? What is a rare sequela of LCMV infection

A

Aseptic meningitis

  • sudden onset deafness can occur, but usually resolves with no serious neurological problems
  • Cases of LCMV are rarely fatal

Neuro Block 2 (11 decks)

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