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Viruses (Rotavirus (Production of digestive enzymes is limited, Patient…
Viruses
Rotavirus
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There is shortening and atrophy of villi, flattening of epithelium and stripping of microvilli - decreases surface area of small bowel
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Following ingestion, rotavirus infects epithelial cells of small bowel
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Basic Properties
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No cell wall, has outer protein coat surrounded by lipid envelope
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Replication
- Replication: Production of viral nucleic acid and viral proteins. Genome is replicated via transcription and translation of virus mRNA
- Assembly: Can occur in nucleus e.g. herpes virus
Can occur in cytoplasm e.g. poliovirus
Can occur in cell membrane e.g. influenza virus
- Release: Done by lysis of cell e.g. rhinovirus
Also done by exocytosis e.g. HIV, influenza
Even though only a few virus molecules will enter the host, millions will leave after replication
- Interaction with host cell: Virus uses cell materials to replicate.
- Cell entry: Only viral core (contains nucleic acid) enters cytoplasm. Protein coat is left behind
- Attachment: Virus attaches to host cell receptor e.g. HIV on CD4 receptor
Hepatitis B
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If patient recovers, they will be a carrier.
80% are asymptomatic
In a carrier there is a steady state between viral replication and host defence. There is limited viral replication, hepatocyte regeneration, proliferation of hepatocytes and hepatocyte destruction by CD8 T cells which recognise the HBV proteins as foreign
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How They Cause Disease
Damage by modification of host cell structure e.g. physical modification by HIV, functional modification by rotavirus
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Damage cell by direct destruction e.g. poliovirus, HIV, influenza
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Polio
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Replicates in gut, travels through blood to the brain where it destroys brain cells
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Varicella Zoster Virus
Rash is on face, scalp, trunk. Develops into papules
A type of herpes virus
There are 8 herpes viruses:
- Herpes simplex 1: coldsores
- Herpes simplex 2: genital
- Varicller-zoster
- Esptein-Barr: glandular fever
- Human cytomegalovirus
- Human herpes virus 6
- Human herpes virus 7
- Karposi's sarcoma
Incubation period of 14-21 days - fever, malaise, headache
Complications: Pneumonia, pneumonitis, viral dormancy in dorsal root ganglion - when reactivated in adults, this presents as shingles
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Herpes Zoster Virus
Clinical presentation: Neuropathic pain, tingling first then rash
Red flag if rash in multiple dermatomes/peripheral dermatomes as this is unusual and suggests immunocompromise e.g. HIV
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