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Microbiology test 3 > Viral Skin Infections (session 21) > Flashcards

Viral Skin Infections (session 21) Flashcards

1
Q

Measles aka/overview

A

Rubeola
a classic childhood exanthema (skin eruptions)
can be severe in malnourished and/or vit A deficient ppl.

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2
Q

Measles phases

A

(measles=rubeola)

  1. incubation period (10-14 days): multiplication in resp epithelium & lymph nodes, viremea, 2ndary viremia
  2. prodromal stage: 1-12 days post infection, high fever, coryza, persistent cough, conjunctivitis (the 3 Cs), KOPLIK’S SPOTS on bucal mucosa (diagnost)
  3. Rash: begins 3-4 days post-prodrome, highest fever (sickes patient), begins below ears, spreads
  4. Resolution: risk in antibody titres, viremia stops, rash fades in same order it appears
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3
Q

Koplik’s spots: what, where

A

on buccal mucosa are diagnostic for Rubeola (measles)

-occur during the prodromal stage

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4
Q

Measles complications

A

pneumonia (accounts for most measles deaths; malnourished & aged at greatest risk, bacterial superinfection common)
diarrhea
CNS involvement: acute symptomatic encephalitis (15% fatality, .5% encephalitis, SSPE:subacute sclerosing panencephalitis very rare in US)

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5
Q

Measles Hosts & Epidemiology

A

humans & monkeys=only known hosts
no healthy carrier state is known
primarily a dz of kids (most immune by age 10, rare in infants under 6 mos-maternal immunity)
transmission by respiratory droplets (highly contagious)

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6
Q

Measles dx

A

rash &/or Koplik’s spots
serology
FA test on cells obtained from swabs of pharynx, nasal & buccal cavities-multinucleated giant cells

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7
Q

Measles prevention

A 
MMR vaccine (measles [rubeola], mumps & rubella)
since vaccine, 99% reduction in US
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8
Q

MMR vaccine schedule

A

initiation before school entry
15 mos: first dose
4-5 yrs: second dose
may vaccinate kids under 15 mos w/monovalent measles vaccine if exposure deemed likely (revaccinate at 15 mos)
recent outbreaks may lead to routine 3rd application of vaccine (booster)

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9
Q

Are all MMR vaccines the same?

A

NO, US uses MMRII

live, attenuated vaccine NOT suitable for all patients

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10
Q

Measles outbreaks in the US

A

most involved non-vaccinated persons & air travel to foreign locations
UK measles outbreak 2013: acceptance rate for vaccine had fallen
-large scale epidemic emergency; Andrew Wakefield

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11
Q

German Measles aka & description

A

Rubella=”little red”
mild exanthematous dz that resembles measles superficially
close & prolonged contact probably needed for infection
Kids often escaped infection

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12
Q

Rubella Complications

A

Congenital Rubella Syndrome (CRS)-maternal infection (viremia) may lead placental infection & fetal infection
Substantial risk to fetus: cardiac defects, eye defects, hearing loss (may be profound CNS involvement)

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13
Q

Outcome of CRS is affected by what?

A

timing of infection is critical element in outcome (early in pregnancy is worst)
1st mo: 50% risk of CRS
2nd mo: 30%
3rd mo: 20%
4th mo: exceedingly los
vaccination has nearly eliminated CRS in US

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14
Q

Rubella tx & prevention

A

symptomatic relief
prevention-MMR vaccine:
live virus vaccine
avoid infection in pregnancy first trimester
do not administer vaccine to pregnant pts

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15
Q

Herpes simplex virus (HSV) unique props

A

2 unique props infl. dz capacity of HSV:

  1. capacity to invade & replicate in CNS
  2. ability to establish latent infections (they are permanent)
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16
Q

HSV clinical manifestations

A

HSV causes primary infection (may be asymptomatic) that will resolve and establish quasi-stable state of latency subject to reactivation (recrudescence)
SHALLOW VESSELS ON AN ERYTHEMATOUS BASE
BALLOONING PATHOLOGY, VESICLES CRUST OVER (painful)

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17
Q

how does HSV become latent, what is latency like?

A

retrograde transport of virus through sensory neurons & ultimate infection of dorsal room ganglia
LATENCY IS LIFE-LONG (reactivation via: sunlight, menses, nutrition, stress)
continued spread is halted by cell & humoral immune processes

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18
Q

HSV: does asymptomatic shedding occur?

A

yes, it is frequent, perhaps up to 2/3 of virus shedding days are asymptomatic & most transmission occurs at these times or from ppl who don’t know they are infected

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19
Q

HSV latency rule of thumb

A

probability of recrudescence is greater in individuals w/larger & more extensive initial outbreaks

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20
Q

HSV latency

A

recrudescence occurs even in the presence of active humoral & cellular immunity (“cold sores”, “fever blisters” on vermillion border of lips)
-lesions generally heal w/out scarring

21
Q

HSV epidemiology

A

humans are the only reservoir
spread by DIRECT CONTACT w/vesicular fluid, saliva & secretions
-ASYMPTOMATIC VIRUS SHEDDING POSSIBLE
HSV-1 infection is common & often occurs early in life, >90% seropositive (rates vary w/SES)
HSV-2 infection tends to occur later & correlate w/sexual activity

22
Q

HSV diseases (3)

A
  1. Oral herpes (90& HSV-1)
  2. Genital herpes (90% HSV-2)
  3. Neonatal HSV infection (infection in utero or MOST COMMONLY during BIRTH CANAL PASSAGE)
23
Q

HSV dx

A
  1. direct samples of lesions for virus or components
  2. ballooning pathology & presence of enlarged & fused cells (Tzanck smear)
  3. FA assay for viral antigens
  4. rapid tests that reveal patient antibodies to HSV, great utility in confirming dx in patients w/sporadic outbreaks or poorly defined lesions
24
Q

HSV tx

A

Acyclovir (ACV)-most prescribed antiherpes agents, may be used to suppress HSV recrudescence
viral enzyme thymidine kinase phosphorylates ACV
-this molecule will halt viral DNA replication b/c it lacks a 3’-OH group & cannot allow the polymerization of more bases

25
Chickenpox: causative agent
varicella-zoster virus
26
Varicella-zoster virus causes what?
BOTH chickenpox & shingles | VZV is a herpes virus (sometimes known as Herpes zoster)
27
varicella zoster virus clinical manifestations
1. asymmetrical vesicular rash that sometimes follows an obvious dermatomal pattern 2. fever, malaise, HA, neuralgia w/ PRURITIC lesions that are often secondarily infected
28
How does VCV infect
Varicella virus infects through conjunctiva or respiratory tract mucosa - replicates in regional lymph nodes, primary viremia 4-6 days after infection - replicates in liver & spleen generating a secondary viremia (coincident w/rash) 10-14 days post-infection
29
VZV epidemiology
- HUMANS are the ONLY KNOWN RESERVOIR - seasonal occurance (peaks in winter-spring) - highest incidence in 5-9 yos (>90% of all cases in ages 1-14 years) - most (C) US childhood exanthema-3,000,000 cases/year - spreads in resp., conjunctiva, vesicle secretions - highly contagious (90% attack rate) - incubation period is 15 days - pt most contagious 1-2 days before appearance of lesions & 4-5 days after lesions appear
30
Prodromal symptoms of VZV & who exhibits them
prodromal sxs in OLDER CHILDREN & ADULTS: fever, malaise, HA, myalgia, anorexia ABSENT IN YOUNGER KIDS
31
VZV dx
clinical findings rash & fever may be tricky to distinguish from HSV in immunocomprimised & neonates excoriated lesions may look like insect bites
32
VZV tx
no specific therapy is needed in normal host ASA is NOT RECOMMENDED->REYE's SYNDROME RISK) Acyclovir effective
33
VZV prevention
vaccines: VARIVAX, MMMRV & VariZIG human immunoglobulin | - live, attenuated virus-may cause mild dz episode in recipients
34
Vaccines for VZV: 3 issues
1. BREAKTHROUGH CASES (mild chickenpox in vaccinated ppl after exposure) are well documented 2. VZV INFECTION DURING PREGNANCY OR AT TIME OF BIRTH CAN=SIG. CONGENITAL/NEONATAL DZ-healthcare pp. requested to report inadvertent vaccine admin during pregnancy 3. vaccine DOES NOT guarantee protection from shingles
35
Shingles: how does one acquire this?
Recrudescence of a prior VZV (chickenpox infection) | -REQUIRES PRIOR CASE OF CHICKENPOX OR VACCINATION AGAINST CHICKENPOX
36
Shingles: clinical manifestation
PAINFUL lesions "searing, burning, stabbing", pain may precede rash by days to weeks -areas of redness evolved to papules & vesicles in 24 hour period low grade fevers, anorexia UNILATERAL DERMATOMAL DISTRIBUTION (SHARP LIMITS): "zoster"=belt or stripe 10% have involvement of ophthalmic branch of 5th cranial nerve, 20% have ocular involvement
37
Shingles tx
self-limited dz, but painful: take steps to control lesion pain postherpetic neuralgia is most (C) complication, pain may persist for months SHINGLES IS NOT DIRECTLY TRANSMISSIBLE
38
Shingles prevention
Zostavax for pts over age 50 high potency ZVZ vaccination to boost immunity same virus used in Varivax, BUT MUCH HIGHER POTENCY
39
Human Herpes Virus-6: aka, prevalence, presentation
aka Roseola Infantum or 6th dz VERY PREVALENT, unrecognized until proper culture system available -EXANTHEM SUBITUM: sequence of fever followed by rose-colored rash
40
HHV-6 clinical manifestion
regularly acquired viral infection of childhood: 30% of kids 6 mos to 3 yold sustained fever 2-5 days, 39-41*C (child often looks remarkable well despite high fever) ER visits due to high fever w/out obvious source
41
HHV-6 diagnosis
detection of antibody by EIA | DNA sequence detection by PCR amplification
42
HHV-6 treatment/prevention
DON'T NEED TO isolate NO antiviral therapy required NO primary preventative measures exist
43
Parvovirus B19 aka
"Fifth disease" | erythema infectiosum
44
Parvovirus B19 clinical manifestation
prodrome: several days, mild sxs, fever, HA, malaise, myalgia, resp. sxs, sometimes nausea, vomiting followed by skin rash: SLAPPED CHEEK APPEARANCE, circumoral sparing, resolves in 1-2 weeks can see maculopapular rash on limbs & trunk many adults have ARTHRITIS or ARTHALGIA ALONE w/out and preceding or concurrent sxs
45
Adult w/Parvovirus B19 may present as
sudden arthritis or arthralgia along wout any preceding or conceurrent sxs
46
Parvovirus B18 epidemiology
epidemics in late winter & spring worldwide distribution highest incidence of infection in school age children
47
Parvovirus B19 dx
facial rash helpful detection of anti B19 IgM antibody epidemic outbreaks aid dx
48
Parvovirus B19 tx & prevention
most patients make a rapid & full recovery relief of sxs: NSAIDs immunoglobulin available for anemic patients
49
HPV: what is it & how is it tx
HPV is an STI HPV 6 & 11: ano-genital warts HPV 16 & 18: cervical dysplasia Gardasil & Cervarix vaccines are now licensed for males & females ages 9-26

Microbiology test 3 (8 decks)

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