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B9W3 > PBL 1 > Flashcards

PBL 1 Flashcards

1
Q

Which virus causes chickenpox and shingles?

A

Varicella-Zoster virus

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2
Q

what type of virus is varicella zoster virus?

A

a strain of herpes virus

dsDNA enveloped virus

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3
Q

how does the varicella zoster virus enter host cells?

A

it fuses its membrane with the host cell membrane and releases its capsid inside the cell
capsid binds to nucleus and injects the viral DNA inside where they are transcribed into RNA and then translated into capsid proteins at the ribosome
capsid and viral DNA fuse together in the Golgi complex to form the lipid membrane
newly formed viruses leave the cell

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4
Q

how is the varicella zoster virus transmitted?

A

respiration- sneezing and coughing

direct contact with oral or skin lesions

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5
Q

outline primary viremia of varicella?

A

virus comes into contact with respiratory mucosa or skin of person and replicates in the epithelial cells. 4-6 days after infection the virus infects reticuloendothelial cells in the liver and spleen

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6
Q

outline secondary viremia of varicella?

A

2 weeks after primary viremia the virus infects immune cells (particularly T cells). infected T cells express proteins which bind to skin cell receptors which allows the release of the virus. the virus then infects keratinocytes,

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7
Q

what are Tzanck cells?

A

when infected keratinocytes fuse together to form multi-nucleated cells

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8
Q

what causes the small initial lesions on the skin in varicella?

A

uninfected cells secrete interferons to attempt to inhibit viral protein synthesis - this causes the lesions

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9
Q

outline the pathophysiology of shingles (herpes zoster)?

A

virus infects sensory neurone in the skin during varicella and they travel retrogradely to the ganglia
when the immune system kicks in to remove varicella, most of the viruses in the body are eliminated but those in the ganglia are spared
these viruses can remain dormant for Many years until the immune system weakens and the virus can be reactivated, travel up the neurone and infect the innervated dermatome

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10
Q

what are symptoms of varicella?

A

fever, headache, weakness, rash and spots, painful sores on mucosal surfaces

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11
Q

describe how the rash in varicella changes over time?

A

1-3 weeks after exposure, flat/red/itchy lesions (macule) form, overtime these become elevated (papules) and eventually they become small-fluid-filled vesicles

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12
Q

when do scabs form over vesicles in varicella?

A

1-2 days after appearance

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13
Q

how often do new crops of lesions appear in varicella?

A

every 3-5 days

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14
Q

what are macules?

A

a flat, distinct, discolored area of skin less than 1 cm wide

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15
Q

what are papules?

A

a raised area of skin tissue that’s less than 1 centimeter around.

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16
Q

when is varicella infectious from and to?

A

2 days before the spots appear to until they crust over

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17
Q

what are the symptoms of shingles?

A

unilateral rash that causes pain, itching and tingling that can last up to 4 weeks

18
Q

how long can pain last for in the affected dermatome in shingles?
why?

A 
90 days (postherpatic neuralgia) 
nerve fibres are damaged so messages between skin and brain get confused = chronic pain
19
Q

can you catch chickenpox from someone with shingles?

A

yes. usually only if you haven’t had it before

20
Q

can you catch shingles from someone with chickenpox?

A

no

21
Q

can you catch shingles from someone with shingles?

A

no

22
Q

what are some common complications of varicella zoster?

A 
bacterial infections of the skin
septicaemia
TSS
necrotising fasciitis
osteomyelitis
septic arthritis
23
Q

how can you diagnose the varicella zoster virus?

A

skin lesion appearance
Tzanck test to look for multinucleate giant cells in the fluid of vesicles
blood test for varicella antibodies
PCR to look for viral DNA

24
Q

how do you treat varicella zoster?

A 
topical antipruritic meds
analgesics
anti-inflammatory meds
antivirals
varicella zoster immunoglobulin
varicella vaccine
zoster vaccine
25
Q

why shouldnt you task aspirin when you have varicella?

A

use of aspirin with varicella has been associated with Reye’s syndrome (toxic build up of ammonia and swelling of liver and brain)

26
Q

what are antivirals?

A

a class of medication used for the treatment of viral infections

27
Q

what antivirals do we use to treat influenza?

A

M2 ion channel inhibitors, neuraminidase inhibitors, endonuclease inhibitors

28
Q

how do M2 ion channel inhibitors work?

A

they block the viruses entry into the cell

29
Q

what do endonuclease inhibitors do?

A

blocks the transcription of mRNA

30
Q

what do neuraminidase inhibitors do?

A

stop the release of viruses from the infected host cells

31
Q

which types of drugs do we use to treat HIV?

A

entry inhibitors, reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, integrate inhibitors, protease inhibitors

32
Q

how do non-nucleoside reverse transcriptase inhibitors work?

A

block HIV reverse transcriptase which is used to convert its RNA into DNA = prevents replication

33
Q

which antivirals do we use to treat hepatitis?

A

nucleoside and nucleotide analogues, NS3/4A protease inhibitors, NS5A inhibitors and NS5B polymerase inhibitors

34
Q

how do nucleoside and nucleotide analogues work to treat hepatitis?

A

by inhibition of HBV polymerase activity resulting in decrease of viral replication.

35
Q

which drugs do we use to treat herpes?

A

acyclovir, ganciclovir and penciclovir

36
Q

how does aciclovir work?

A

It’s converted to acyclovir triphosphate, which competitively inhibits viral DNA polymerase

37
Q

how does ganciclovir work?

A

its triphosphate form inhibits viral DNA polymerase

38
Q

how does penciclovir work?

A

its triphosphate form inhibits viral DNA polymerase

39
Q

why do most people not require antiviral drugs?

A

as they will have a mild illness and will recover quickly so the risks of side effects may outweigh the benefit

40
Q

who are the candidates for antivirals?

A

those over 65, have chronic disease, anyone under 4 and anyone with a compromised immune system

41
Q

what are some common side effects of antivirals?

A

nausea and vomiting, diarrhoea and stomach ache, headache

42
Q

why are antivirals tricky to develop?

A

because viruses are so small and mutate quickly

viruses are also within host cells so its hard not to damage the host

B9W3 (12 decks)

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