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Clinical pathology > Viral and prion pathogens > Flashcards

Viral and prion pathogens Flashcards

1
Q

Virus features

A
  • simple micro-organisms
  • Not capable of independent existence
  • Need a host cell to survive
  • Genome in middle, Capsid (protein coat) around, lipid bilayer at superficial surface
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2
Q

Virus life cycle

A
  • Adsorption - onto surface of host cell
  • Penetration - endocytosis
  • Uncoating - genome released from phagosome
  • Synthesis - Genome is replicated by enzymes
  • Assembly - virus components assembled
  • Release - virus released from host by budding
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3
Q

Viral classification

A

Viruses are classified by their:
genetic material - DNA vs RNA
presence or absence of an envelope

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4
Q

Herpes viruses

A

Double stranded enveloped DNA viruses

  • 9types
  • Characterised by their ability to establish latency and reactivate
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5
Q

HSV - 1

A

cold sores

  • transmitted by direct contact. Latency in sensory nerve ganglion- periodic reactivation
  • Shows as vesicles/ulcers and Encephalitis (brain inflammation)
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6
Q

HSV-2

A

genital herpes

  • Transmitted by direct contact. Latency in sensory nerve ganglia - periodic reactivation
  • Shows as vesicles/ulcers, Meningitis and neonatal herpes (vertical transmission)
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7
Q

Varicella zoster virus

A

Causes chicken pox, herpes zoster and shingles.

  • Transmitted by direct contact, respiratory droplet.
  • Latency established in dorsal root ganglia of CNNS
  • Chicken pox = wide rash
  • zoster,shingles = unilateral vesicles
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8
Q

Epstein Barr virus

A

Glandular fever

  • Transmitted by saliva and genital secretions
  • Infectious mononucleosis is the primary infection - tonsillitis, fever etc
  • Reactivation from latency in B cells
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9
Q

Cytomegalovirus

A

causes CMV

  • Transmitted by saliva, donated blood.
  • Latency in dendritic cells
  • Infectious mononucleosis is primary infection
  • Congenital CMV infection- infants with retinitis, microcephaly and deafness
  • Reactivation in immunosuppressed patients can cause retinitis and colitis
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10
Q

Rhinovirus

A

Common cold

  • Transmitted by droplets and aerosolised respiratory droplets
  • Common cold symptoms
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11
Q

Coronaviruses

A
  • Alpha and beta viruses
  • Transmitted airborne/droplets
  • causes COVID19, MERS, SARS
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12
Q

Influenza

A

3 types A,B,C
A = mutates regularly
- 2 important surface proteins H and N have multiple variants
- Transmitted by droplets
- Primary influenza illness = fever, myalgia then cough headache etc
- Secondary infection = bacterial lung infection

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13
Q

Respiratory syncytial virus

A
  • commonest in young children
  • Transmitted airborne/droplets
  • Causes Bronchiolitis - inflammation of bronchioles - cough, wheeze, hypoxia
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14
Q

HIV - Human immunodeficiency virus

A
  • Transmitted vertically, sexually, needlestick
  • HIV targets CD4 cells
  • Asymptomatic chronic infection occurs
  • AIDS patient become vulnerable as viral load rises and CD4 count falls
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15
Q

Hepatitis A

A

Faeco-oral

  • Nausea, myalgia, fevers
  • associated with contaminated water
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16
Q

Hepatitis E

A

Faeco-oral

  • Nausea, myalgia, fever
  • associated with pigs/undercooked pork
  • causes fulminant hepatitis with high mortality in infected pregnancy women.
17
Q

Hepatitis B

A

Vertical, sexual transmission

  • After transmission, acute clinical hepatitis may occur
  • Hep B is then cleared or chronic - chronicity is inversely related to age at infection
  • Chronic hepatitis -> cirrhosis -> hepatocellular carcinoma
18
Q

Hepatitis C

A

Transmitted my contaminated instruments (needles)

  • can cause acute clinical hepatitis - 85% of which will become chronically infected
  • can cause HCC overtime
19
Q

Norovirus

A

Transmitted via the GIT, ingestion of aerosolised vomit particles
- Causes a lot of vomiting

20
Q

Rotavirus

A

Transmitted via GIT, faeco-oral, contaminated food.

  • Causes fever, vomiting and diarrhoea
  • It’s a virus of childhood (80-100% infected by 3)
21
Q

Enteroviruses

A
  • more than 70 types
  • Transmitted Faeco-oral, contaminated food/water
  • Replicates in gut nut does not act there
    -gut -> lymph nodes ->blood
    Causes:
  • fever-rash syndromes
  • Meningitis
  • Polio
22
Q

Mumps

A

Very infectious - droplets, saliva

  • causes acute parotitis (salivary glands)
  • Orchitis (testes)
  • Meningitis
23
Q

Measles

A

Highly infectious - droplet transmission

  • Primary measles - fever, cough, coryza, conjunctivitis
  • acute post infection encephalitis
  • Subacute sclerosing pan- encephalitis - degenerative and fatal disease of CNS
24
Q

Rubella

A

Droplet transmission

  • Primary rubella - mild illness, fever, arthritis in some adults
  • Congenital rubella - Classic triad - bilateral cataracts, sensorineural deafness, cardiac defects
25
Q

Parvovirus B19

A

Droplet transmission

  • causes transient anaemia
  • Erythema infectiousum = fever, red rash to cheeks
  • Transient aplastic crisis- affects those with high RBC turnover
  • Infection in pregnancy - can cause foetal loss in first 20 weeks
26
Q

what is a prion

A

A prion is a small infectious particle containing protein but NO NUCLEIC ACID

27
Q

Human prion diseases share what 4 properties

A
  • manifest in the CNS
  • produce spongiform change in brain tissue
  • Have long incubation times
  • Are progressive and fatal
28
Q

How are abnormal prions formed

A
  • Inherited from genetic defects

- Transmitted via consumption or direct exposure

29
Q

Natural prions can be harmful if they do what 4 things

A
  • Gene mutation causes changes in folding pattern
  • Prion becomes resistant to protease enzyme
  • Prion accumulates abnormally in cell
  • Promotes other proteins to abnormally fold
30
Q

Sporadic Creutzfeld-Jakob disease (CJD)

A
  • very rare 1 in a million
  • Gene mutation
  • progressive ataxia, depression, dementia then death
31
Q

nvCJD directly linked to BSE (bovine spongiform encephalopathy)

A
  • same structure prion as normal CJD

- nvCJD cases associated with consumption of contaminated beef

Clinical pathology (69 decks)

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