Varicella Zoster / Polio / Hepatitis C Flashcards
what is varicella?
chicken pox
what is herpes zoster?
shingles
who does chicken pox infect?
- primary infection in children & young adults
who does shingles infect?
secondary infection in adults
what is the viral structure of varicella zoster?
Linear DNA genome
Icosahedral nucleocapsid
how is varicella zoster transmitted?
Respiratory route of infection
Inhalation of aerosols
Direct contact with virus infected vesicles
Very contagious virus
what is the pathogenesis of varicella zoster virus?
Affects children 2-6 years old (2 week incubation)
Virus infection of upper respiratory tract
Replication in regional lymph nodes
Infection of bloodstream (viraemia)
Replication in internal organs (liver and spleen)
Replication in capillary endothelial cells and skin (chickenpox vesicles)
Latency in dorsal root ganglia
what is the symptoms of varicella zoster virus?
Appearance of rash on head that quickly spreads throughout body
Rash is composed ofgroups of small, itchy blisters surrounded by inflamed skin
Mild fever
Fatigue
Headache
Flu like symptoms
what are the characteristics of a varicella zoster virus rash?
Rash starts as flat spot (macule)
Changes into clear blister (vesicle) - these are infectious - contain live virus
Then to pustule, which drys out and forms a scab
Scab falls off after about 2 weeks
typical case study:
Eight year old child developed generalised itchy rash that appeared 2 days ago on face as discrete red spots
Spots developed into small vesicles and spread over body
Fever (37.9 0C), tiredness and headache
On examination patient is febrile with itchy rash and flu like symptoms
what is it?
varicella zoster virus
what are the complications of varicella zoster virus?
Staphylococcus and Streptococcus infections of vesicles - especially if scratched
Immunocompromised patients more extensive eruptions, haemorrhagic blisters, skin necrosis, secondary bacterial infections
Virus can persist in dorsal nerve ganglia in body for many years
May lead to re-occurrence as shingles in adult
what are the characteristics of shingles?
Reactivation of varicella zoster virus during adulthood
4-5 days before shingles rash, get pain & 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 – when vesicles crust over
what are the characteristics of shingles rash?
Vesicles are infectious
Cause chicken pox in children or adults not previously exposed
CAN NOT give shingles to another adult
what is the name of the organism that causes polio?
Enterovirus genus
what is the genome characteristics of polio?
Non-enveloped
Single stranded, positive sense,RNA genome
Icosahedralcapsid
“Positive sense”
how is polio transmitted?
Transmission faecal-oral route
respiratory route
how prevalent are the symptoms of polio?
90% people have no symptoms or very mild symptoms
1 in 200 irreversible paralysis (legs) when virus spreads to central nervous system
what is the pathogenesis of polio?
Virus spreads along neurons and destroys nerve cells that activate muscles
Causes acute flaccid paralysis - affected muscles do not function & limb becomes floppy
Most severe cases - bulbar polio - virus attacks nerve cells of brain stem reducing breathing capacity and causing difficulty in swallowing and speaking
5 - 10% death rate - breathing muscles are immobilized
what are the 4 types of polio vaccination?
Oral polio vaccine (OPV)
Monovalent oral polio vaccines (mOPV1 & mOPV3)
Bivalent oral polio vaccine (bOPV)
Inactivated polio vaccine (IPV)
what are the genome characteristics of hep c?
Positive sensesingle strandedRNA virus
Cell membrane derived envelope
Icosahedral nucleocapsid
what is the genus of hepatitis c?
Hepacivirus Genus
what are the characteristics of hep c?
Replicates mainly inhepatocyte cells of liver
Range of severity - mild illness for few weeks - serious lifelong condition that can lead liver cirrhosis or cancer
> 350 000 people / year die from hepatitis C-related liver disease
No vaccine
what is the viral structure of hep c?
single-stranded RNA
nucleocapsid
envelope
envelope proteins
how is hepatitis transmitted?
Transmitted through exposure to infectious blood
Contaminated blood transfusions, blood products & organ transplants
Injection with contaminated syringes & needle-stick injuries in health-care setting
Injection drug use
Babies born to hepatitis C-infected mother
Less common transmission - sex with infected person or sharing personal items contaminated with infectious blood
