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CSIM 1: Virology Strand > CSIM 1.15 Viruses Which Cause Rashes > Flashcards

CSIM 1.15 Viruses Which Cause Rashes Flashcards

1
Q

What are the types of viral rashes?

A

• Maculopapular
• Vesicular
IMG 40

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2
Q

What are the (learning outcome) viral causes of maculopapular rashes?

A
  • Measles
    • Rubella
    • Parvovirus B19
    • HHV6 & HHV7
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3
Q

What are the (learning outcome) viral causes of vesicular rashes?

A
  • Herpes simplex virus
    • Varicella zoster virus
    • Poxviruses
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4
Q

Where does the virus reside in a vesicular rash and in a maculopapular rash?

A

Vesicular rash:
• Within the lesions

Maculopapular rash:
• Not within lesions (raised redness is just due to the immune response)

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5
Q

What features are looked at when clinically diagnosing the cause of a vesicular rash?

A
  • Typical site
    • Whether lesions are at the same or different stages of development
    • Whether the rash is generalised or dermatomal
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6
Q

What features can give a clue of the causative agent when diagnosing maculopapular rashes?

A
  • Typical prodrome
    • Associated symptoms
    • Lab tests
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7
Q

Describe the virology of measles, mumps and rubella

A 
Mumps and Measles
  •  Single stranded RNA viruses
  •  Negative sense
  •  Enveloped
  •  Paramyxoviridae
Rubella
  •  Single stranded RNA viruses
  •  Positive sense
  •  Enveloped
  •  Togaviridae
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8
Q

Describe the pathogenesis of measles, mumps and rubella

A
  • Spread by respiratory route: aerosol

* Pathology is immune mediated

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9
Q

What is the difference between aerosol and large droplet respiratory transmissions

A

The size of the droplet, and thus the range of transmission through coughing and sneezing

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10
Q

What is the incubation period and infectious period of measles?

A

Incubation: 10-14 days

Infectious:
• 2-3 days before the rash
• 5 days after the rash

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11
Q

What are the clinical features of measles with regard to the prodrome and the rash

A 
Prodrome
  •  High fever
  •  Cough, Coryza and Conjunctivitis
  •  Koplik spots
  •  Miserable
Rash
  •  Maculopapular
  •  Face and neck
  •  Spreads to trunk
  •  4-5 days duration
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12
Q

What is coryza?

A

A running nose

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13
Q

What are Koplik spots?

A

White spots on the buccal muscosa (inner cheek lining)

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14
Q

What are the complications of measles?

A

• Secondary bacterial infections due to immunosuppression

• Acute measles post-infectious
encephalitis

• Subacute sclerosing panencephalitis

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15
Q

How common is acute measles post-infectious encephalitis? When does this occur? How fatal is this?

A

1 in 1000 cases
7-10 days after rash fades
15%

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16
Q

How common is subacute sclerosing panencephalitis? When does this occur? How fatal is this?

A

1 in 100,000 cases
6-8 years after measles
100%

17
Q

Who are the risk groups for measles? What is given to these groups if infected?

A

Immunocompromised patients
• Giant cell pneumonitis
• Measles inclusion body encephalitis

Pregnant women
• Stillbirth

Neonates
• More severe disease

These groups should be given human normal immunoglobulin treatment

18
Q

How is measles diagnosed?

A

Throat swab of nasopharyngeal secretions
• Immunofluorescence or PCR performed

Antibody screening
• IgM for infection (present acutely 2 days after rash onset)
• IgG for past infection (present for life)
• Salivary screening

19
Q

How is measles managed?

A

No antiviral available

Infection control precautions are taken

20
Q

What form of vaccine is given for measles?

How is this administered?

A

Live, attenuated measles (mumps and rubella) strains

In 2 doses 12-18 months apart given to pre-school children

21
Q

What is the efficacy of measles vaccine?

A

90% for each dose

99% total

22
Q

How is rubella spread? When are patients infectious?

A
  • Respiratory spread
    • Incubation 14-21 days
    • Infectious 7 days before their rash to 7 days after it appears
23
Q

What are the clinical features of rubella with regard to the prodrome and the rash?

In what proportion of the population is rubella asymptomatic?

A

Prodrome
• Lymphadenopathy 7 days before rash: cervical, postauricular, subocciputal

Rash
• Maculopapular
• Face to trunk to limbs

Asymptomatic in 25%

24
Q

What are the complications of rubella?

A

Arthralgia

Congenital rubella syndrome

25
Q

Describe congenital rubella syndrome

A 
If mother gets rubella before 12 weeks gestation, there is a 75% risk of severe malformation:
  •  Jaundice 
  •  Petechia
  •  Hepatomegaly
  •  Cardiac and ocular defects

Before 16 weeks is sensorineural hearing loss

26
Q

How is rubella diagnosed?

A

Antibody screening
• IgM for infection
• IgG for past infection (or vaccination)

27
Q

How is rubella managed?

A

No antiviral available

Infection control precautions

Termination offered if rubella confirmed in

28
Q

How effective is one dose of the rubella vaccine?

A

99% (one dose)

29
Q

Describe the virology of parvovirus B19

A
  • Single stranded DNA virus (only one that is relevant)

* Non-enveloped

30
Q

Which cells do parvovirus B19 infect?

A

Red blood cell progenitors (not mature RBCs as these do not have nuclei)

31
Q

Describe the transmission and infectious window of parvovirus B19

A
  • Respiratory spread
    • Incubation 14-21 days to rash onset
    • Infectious 7 days before rash, not infectious after rash present
32
Q

What are the clinical features of parvovirus B19

A
  • Subclinical/mild
    • Nonspecific prodrone
    • Slapped cheek rash
    • Maculopapular rash on trunk
    • Arthralgia/arthritis
33
Q

Who are high risk groups to parvovirus B19?

A
  • Haemolytic disorders (because blood cell lifespan is shorter and so due to loss of progenitors anaemia can result)
    • Immunocompromised (persistent anaemia because these patients cant clear the virus)
    • Pregnancy
34
Q

What are the pregnancy risks associated with parvovirus B19

A

Foetal loss

Foetal hydrops
• Virus destroys erythroid cells causing anaemia
• Heart tries to compensate leading to left ventricular failure
• Fluid accumulates

35
Q

How is parvovirus B19 diagnosed?

A

Diagnostic tests not needed if uncomplicated

Antibody screening
• IgM for infection
• IgG for past infection

Amniotic fluid PCR

36
Q

How is parvovirus B19 managed?

A

No antiviral available

Foetal blood transfusion

37
Q

Describe the virology of enteroviruses

A
  • Non-enveloped

* Positive sense single stranded RNA viruses

38
Q

How are enteroviruses transmitted?

A

Faecal-oral transmission

39
Q

Name the common poxviruses

A
  • Orf

* Molluscum contagiousum

CSIM 1: Virology Strand (12 decks)

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