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Viral infections Flashcards

1
Q

Describe the steps in a viral life cycle.

A

Step 1: Viral attachment

  • binding sites on the virus
  • receptors (+/- co receptors) on plasma membrane of cells
  • cell must be permissive (right intracellular components for the virus to replicate)

Step 2: Entry
- take seconds to several minutes

Step 3: Uncoating

  • can take place in:
    1. endosome
    2. cytosol
    3. nuclear membrane
  • nucleic acid needs to get in the right place to replicate

Step 4: Synthesis of viral components

  • requires viral mRNA to enable viral polypeptide/nucleic acid to be synthesised by the cell machinery
  • positive polarity = RNA that has been brought in on the ribosomes has the right conformation to be used as mRNA
  • negative polarity = mirror image of what the mRNA is supposed to be - use reverse transcriptase for correct conformation

Step 5: Assembly + release

  • new virion is assembled after synthesis of viral proteins and nucleic acid
  • released by: cell lysis (causes pathology as there is cell death); budding (without cell death)
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2
Q

Give examples of enveloped and non-enveloped DNA viruses.

A 
Enveloped:
1. herpes virus 
- HSV
- cytomegalovirus
- varicella zoster 
- epstein barr
- HHV 6/7/8
2. hepatitis B
3. Pox virus 
enveloped = cause rashes

Non-enveloped:

  1. Papillomavirus
  2. adenovirus
  3. parvovirus

(PAP)

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3
Q

How does herpes virus present in older children/adults vs neonates?

A

Older children/adults:

  • herpes labialis/cold sore
  • herpetic whitlow (painful infection affecting fingers/thumbs)

Neonates:

  1. Disseminated HSV
  2. HSV encephalitis
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4
Q

What is cytomegalovirus? What are the common symptoms?

A

Self-limiting disease (will resolve by itself)
Often subclinical
May present as a mononucleosis-like illness
(sore throat, fever, lymphadenopathy)
it is a severe disease in the immunosuppressed (colitis, retinitis)

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5
Q

What are the S+S of congenital CMV? What are the potential complications? How is it treated?

A

90% are asymptomatic

S+S:
extramedullary haematopoiesis = affects the bone marrow
enlarged liver/spleen

Complications:
long term sensorineural hearing loss

Treatment:
IV ganciclovir or valganiclovir (pro-drug of ganciclovir)
- works by inhibiting DNA synthesis
- is an oral medication 
- may cause issues with blood count
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6
Q

What are the complications of Varicella zoster virus?

A

Can cause secondary infections (Group A Strep has a predilection for VZV lesions)
* most often severe in adults (especially pregnant women)

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7
Q

When is epstein barr virus most symptomatic? What are the symptoms? How is this virus spread?

A

More symptomatic in older children/young adults (15-25); usually asymptomatic earlier in life

S+S:
mononucleosis-like symptoms
petechiae on hard palate

Spread:
by saliva (therefore airborne + exchange of fluids)
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8
Q

What is HHV 6+7 also known as? At what age is it common? What are the S+S?

A

Roseola infantum/exanthema subitum
Common between 6 months - 2 y/o

S+S:

  • sudden onset of high fever
  • lasts a few days + then suddenly stops
  • followed by appearance of a rash
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9
Q

What are the stages of Hep B infection? What is the consequence of chronic Hep B infection?

A

Stages:

  1. immunotolerant phase: immune system does not fight the infection, symptoms will not appear yet
  2. clearance phase: immune system will become active and begin to clear the virus - this is when symptoms will begin to appear

Consequence of chronic Hep B infection?
Cirrhosis of the liver
Hepatocellular carcinoma

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10
Q

How is the risk of transmission of infections from a pregnant woman to her baby determined?

A

This depends on e-antigen status (marker of infectivity)
eAg positive = DNA turning over rapidly = 90% chance of transmitting
eAg negative = not as active

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11
Q

What is the treatment for HepB?

A

Vaccine

Hep B immunoglobulin also given is there is a high risk of transmission

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12
Q

What is Molloscum contagiousum? How are severe cases treated?

A

related to Pox virus
it is a dome-shaped lesion with an umbilicated centre
often found in moist areas (groin, axilla)
spread by direct contact
mild but persists for several years
severe cases (immunosuppressed) treated with cidofovir

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13
Q

What type of cancer can the Papilloma virus cause? Which serotypes are carcinogenic and which cause genital warts? What vaccines are available for HPV?

A

Can cause cervical cancer (Cervarix vaccine)
Serotypes 16 + 18 are carcinogenic
Serotypes 6 + 11 cause genital warts
- Gardasil vaccine for serotypes 6, 11, 16 + 18

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14
Q

What are the S+S of adenovirus?

A

URTI/ pneumonia
Conjunctivitis
Diarrhoea
Disseminated in immunocompromised causing pneumonitis

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15
Q

What type of DNA does parvovirus have? what is the P antigen? How does this viral infection present in neonates vs adults?

A

DNA: single stranded
P antigen:
- parvovirus attaches to the P antigen
- people with the P antigen are much more susceptible to parvovirus
- virus will replicated in rapidly dividing cells
- can cause an aplastic crisis in those with sickle cell/blood disorders

Neonates: asymptomatic or ‘slapped cheeks’
Adult: can cause arthropathy (joints) and foetal loss

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16
Q

Give examples of enveloped and non-enveloped RNA viruses?

A

Enveloped:

  • MMR
  • RSV, influenza, parainfluenza
  • Hep C
  • HIV

Non-enveloped:

  • Rotavirus
  • Enterovirus
  • Hep A
17
Q

What is the incubation period for Measles? What are the symptoms? What are the potential complications?

A 
Incubation: 7-14 days
S+S:
- fever
- cough
- conjunctivitis
- koplik spots 
- rash

Complications:
- subacute sclerosing pan encephalitis

18
Q

What are the symptoms of rubella vs congenital rubella?

A

Rubella:

  • mild rash (usually behind the ears)
  • fever
  • occipital lymphadenopathy

Congenital rubella: (triad of symptoms, EEH)

  • eyes: cataracts, microophthalmia, glaucoma
  • ears: sensorineural deafness
  • heart: pulmonary artery stenosis, VSD
19
Q

What is bronchiolitis? What are S+S? How is it prevented?

A

Viral infection of infants (~70% caused by RSV)
Causes inflammation of the bronchioles

S+S:

  • cough
  • respiratory distress
  • wheeze

Can be severe in preterm

Can be prevented with Palivizumab

20
Q

Why is HIV more severe in infants compared to adults?

A

High viral loads
Rapid progression
No reliable markers
Fewer drugs to treat

21
Q

What vaccines are there to treat rotavirus?

A

RotaTeq and RotaRix

22
Q

How does disseminated HSV in neonates present?

A
  • sepsis-like syndrome
  • hepatitis, coagulopathy
  • high mortality (~70%)
  • treat with aciclovir
23
Q

How does HSV encephalitis present in neonates?

A
  • fever, seizures

- haemorrhagic infarction of white matter (particularly in the temporal lobes)

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