Viral Infections Flashcards
What genus causes the Varicella Zoster Virus?
Varicellovirus Genus
What is the host for varicella zoster virus?
Humans
What are the ‘common’ names for issues caused by varicella zoster virus?
Chickenpox
Shingles
What is shingles?
A secondary infection of chickenpox/ varicella zoster virus which infects adults.
Describe the structure of Varicella zoster virus
- Linear DNA Genome
- Icosahedral nucleocapsid
What type of vaccine is used against Varicella zoster virus?
Live attenuated
Describe the transmission of Varicella zoster virus.
- Respiratory route of infection
o Inhalation of aerosols
o Direct contact with infected vesicles
Very contagious
Where does varicella zoster virus replicate?
In the tonsils and regional lymph nodes.
Can also replicate in the internal organs such as the liver and spleen and in capillary endothelial cells of the skin.
What is the incubation period of varicella zoster virus?
2 weeks.
What is caused when varicella zoster virus infects the blood?
Viraemia
Where does the varicella zoster virus become dormant?
Dorsal root ganglia
Describe the formation of the rash caused in Varicella Zoster Virus (chickenpox).
- Rash on the head o Quickly spreads over the body Starts as a flat spot (macule) Changes to clear blister (vesicle) – • These are infectious because they contain live virus Then forms pustule • Drys out to form scab and crusts over Scab falls off after about 2 weeks
Outline the symptoms of Varicella Zoster Virus (Chickenpox)
- Small groups of itchy blisters surrounded by red inflamed skin
- Mild fever
- Fatigue
- Headache
- Flu like symptoms
Outline the process for diagnosing Varicella Zoster Virus
- Clinical observation
o Itchy rash of discrete spots that initially look flat and red, but later become raised and filled with fluid.
o Use PCR to detect virus in skin lesions (vesicles, scabs, maculopapular lesions).
o Serology
Describe some of the complications that can occur when a person is infected with Varicella Zoster Virus.
- Staphylococcus and streptococcus infections of vesicles
o This is likely if the vesicles have been scratched and so are open to infection. - Herpes zoster opththalmicus
o Infection of the eye leading to blindness - Herpes zoster oticus
o Infection of the ear leading to hearing loss and facial paralysis - Immunocompromised patients more extensive eruptions
o Haemorrhagic blisters, skin necrosis, secondary bacterial infections - Virus latent in sensory neurons in dorsal nerve gaglia for many years
- May lead re-activation as shingles in adult
- Pregnancy – risk of deformities and death of foetus in utero
When is a person infected by Varicella Zoster Virus likely to be infected by Staphylococcus or Streptococcus?
This is likely if the vesicles have been scratched and so are open to infection.
What is Herpes Zoster opthalmicus?
Infection of the eye leading to blindness
What is Herpes Zoster Oticus?
Infection of the ear leading to hearing loss and facial paralysis.
What complications may people infected with Varicella Zoster virus have if they are immunocompromised?
Haemorrhagic blisters, skin necrosis, secondary bacterial infections
Who is the vaccine for Varicella Zoster Virus offered to and how is it given?
- Offered to people in close contact with a vulnerable person or someone with a weak immune system
- Non-immune heathcare workers
Given as 2 separate injections in the upper arm. 4-8 weeks apart.
Outline the progression of Shingles
- Reactivation of varicella zoster virus during adulthood
- 4-5 days before shingles rash, get pain and burning or itching along the nerve routes
- Vesicles appear in clusters or lines along the nerve routes
- Vesicles fill with fluid after 3-4 days then become pustules
- Pain can continue after rash heals
o Post herpetic neuralgia
Can you transmit Shingles?
No - shingles cannot be passed on to another adult.
What genus causes Polio Virus?
Enterovirus genus
Describe the structure of Polio Virus.
Non-enveloped
Single stranded, positive sense, RNA genome
Icosahedral capsid
How is polio virus transmitted?
- Faecal-oral route
- Respiratory route
Outline the symptoms of polio virus ?
- 90% of people have no symptoms or very mild
- 1 in 200 have irreversible paralysis of the legs after the virus spreads to the CNS
How does polio virus cause damage (describe its pathogenesis)
- Virus spreads along neurons and destroys nerve cells that activate muscle movement
- Causes acute flaccid paralysis
o Affected muscles do not function and limbs become floppy
It can also cause Bulbar polio. Virus attacks nerve cells of brain stem reducing breathing capacity and causing difficulty in swallowing and speaking.
What is Bulbar polio?
o Virus attacks nerve cells of brain stem reducing breathing capacity and causing difficulty in swallowing and speaking.
This has a 5-10% death rate given breathing muscles are immobilized.
What vaccines are there against polio virus?
- 1955 Inactivated vaccine (IPV)
- 1962 Live vaccine
- Oral Polio Vaccine (OPV)
- Monovalent oral polio vaccines (mOPV1 and mOPV3)
- Bivalent oral polio vaccine (bOPV)
What genus causes the Hepatitis C virus?
Hepacivirus Genus
Describe the structure of the Hepatitis C virus.
- Positive sense single stranded RNA virus
- Cell membrane derived envelope
Where does the Hepatitis C Virus mainly replicate?
In the hepatocyte cells of the liver.
Describe the transmission of Hepatitis C.
Transmitted through exposure to infectious blood
- Unscreened blood transfusions, blood products and organ transplants
- Needle-stick injuries in health-care settings
- Injection drug use
- Unsafe healthcare
- Babies born to hepatitis C-infected mother
Less common transmission
- Sexual practises leading to blood exposure
- Sex with an infected person
- Sharing personal items with contaminated blood
Outline the diagnosis of Hepatitis C virus.
- Person who is or has been infected at some point in their life
o Detect antibodies against hepatitis C virus
o Recombinant immunoblot assay - Person with chronic virus infection
o Detect hepatitis C virus RNA (PCR/ nucleic acid test)
o Also detect antibodies against hepatitis C virus - Virus genotype testing
o (For genotypes 1-6) - Specialized tests evaluate liver disease, cirrhosis and cancer
Outline the symptoms of Hepatitis C Virus.
- Incubation period of 2 weeks to 6 months
- Approx 80% of people don’t exhibit any symptoms
- Acute symptoms:
o Fever
o Fatigue
o Decrease appetite
o Nausea
o Vomiting
o Abdominal pain
o Joint pain
o Jaundice - Mild illness for few weeks
- Serious lifelong condition
o Liver cirrhosis
o Liver cancer
What vaccines are available against Hepatitis C ?
None
