Viruses

Question 1

What causes the signs and symptoms of viral disease

Answer 1

A culmination of a series of interactions between the virus and the host

Question 2

What are the three outcomes following infection of a host by a virus

Answer 2

Acute infection

Latent infection

Chronic infection

Question 3

What is acute infection and give some examples

Answer 3

Where virus undergoes multiple round of replication resulting in death of the host cell

Poliovirus and influenza

Question 4

What are latent infections and how do they work

Answer 4

Caused by DNA viruses or retroviruses, reflecting persistance of viral DNA either as extracellular chromosome (herpesviruses) or as an integrated sequence within a gene (retrovirus)

During cell growth, the virus genome is replicated and there is production of progeny virus

Question 5

What are chronic viral infections

Answer 5

They are where the virus particles continue to be shed after the period of acute illness

Mark of chronic infection is release of virus particles, sometimes without death of host cell or overt cellular injury, and is usually caused by RNA virus

Associated with defective immune responses that are insufficient to clear the infection

Question 6

What are the main causes of pharyngitis

Answer 6

Viruses - rhinovirus, influenza, EBV, adenovirus

Bacteria - mainly group A strep

Question 7

How is EBV transmitted and what does it mainly cause

Answer 7

Mostly transmitted via intimate contact via saliva containing the virus

Causes infectious mononucleosis (glandular fever)

Question 8

What does an infection with EBV cause within the body

Answer 8

Induces polyclonal B-cell proliferation

Increase in IgG, IgM and IgA

Question 9

What are the symptoms of infectious mononucleosis

Answer 9

Pharyngitis

Lymphadenopathy

Fever

Splenomegalg

Increased levels of liver enzyme in blood

Headache

Malaise

Question 10

Describe the types of influenza viruses

Answer 10

Influenza A - multiple host species. Has antigen shift and drift

Influenza B - no animal reservior. Lower mortality

Influenza C - common cold like

Question 11

Which channels in the viral envelope of influenza are essential for replication

Answer 11

M2 ion channels

Question 12

What virus is also known as bird flu

Answer 12

H5N1 - type of influenza that is highly infectious and causes severe respiratory distress

Question 13

Describe what type of virus VZV is, where it becomes latent and how it spreads

Answer 13

VSV is dsDNA enveloped virus - herpesvirus

Becomes latent in sensory ganglia

Spreads via casual contact and respiratory droplets

Question 14

What are the types of VZV infections

Answer 14

Varicella/Chickenpox

Zoster/Shingles

Reye syndrome

Question 15

Describe how a VZV infection results in chickenpox

Answer 15

Infection spreads to regional lymph nodes -> progeny virus enters blood

It multiplies in the liver and spleen before travelling round the body to infect endothelial cells

It then infects skin epithelial cells resulting in virus containing vesicles of chickenpox

Question 16

Describe the signs and symptoms of varicella

Answer 16

Fever, malaise, headache and abdominal pain before exanthem

Exanthem appears as erythematous macules which are itchy

Question 17

What is Reye syndrome and why does it develop

Answer 17

Reye syndrome is an acute encephalopathy accompanied by fatty liver

Can occur following VZV or influenza infection in children

Use of aspirin or salicylate-containing compounds during the viral illness is associated with Reye syndrome

Question 18

What dorsal root ganglia does VZV commonly stay latent in and how does zoster appear

Answer 18

VZV commonly resides in trigeminal nerve, thoracic and lumbar dorsal root ganglia

Zoster affects patients in a dermatomal distribution

Question 19

What is the treatment for VZV and who is treatment given to

Answer 19

Acyclovir

GIven to immunocompromised, adults and neonates