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SBCP Microbiology > Blood Borne Viruses > Flashcards

Blood Borne Viruses Flashcards

1
Q

What are the three main blood bourne viruses?

A

Hepatitis B, Hepatitis C, and HIV

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2
Q

What type of virus is HBV?

A

Hepatitis B virus is a DNA virus from the family hepdnavirus (‘hep’ ‘dna’)

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3
Q

What type of virus is HCV?

A

Hepatitis C virus is an RNA virus, from the family flavivirus

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4
Q

What type of virus is HIV?

A

Retrovirus and is in the lentivirus sumfamily

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5
Q

What morphological feature do HBC, HCV, and HIV have in common?

A

All are enveloped viruses with a lipid outer surface (do not survive well in the environment or stresses such as desiccation)

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6
Q

What are the three methods of transmission for HBV, HCV, and HIV?

A
  1. Penetrative intercourse
  2. Contaminated blood from needles
  3. Vertical (including breast feeding)

NB all 3 viruses can transmit by any of these routes, lots of local variation in epidemiology

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7
Q

What is principal mode of transmission for HIV?

A

Sexual intercourse

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8
Q

What is principal mode of transmission for HCV?

A

Contaminated blood especially IV drug use

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9
Q

What is principal mode of transmission for HBV?

A

Vertical including breastfeeding

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10
Q

What blood component is tested for a BBV?

A

Serum, therefore send a clotted sample to the virology lab

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11
Q

What can the virology lab test for in a suspected BBV? (4)

A

Type of infection

Past or current
Acute or chronic

How much virus is circulating (infectivity)

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12
Q

What are theranostics?

A

Tests specifically done to guide treatment (monitor response to treatment, or drug resistance, or can look at genotype of hep C)

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13
Q

Which cells are damaged by HBV?

A

Hepatocytes (damage done by immune reaction not the virus)

ie if someone is immunosuppressed they will not have disease

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14
Q

What is the incubation period of HBV?

A

6 weeks to 6 months

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15
Q

Initial symptoms of HBV

A

Nonspecific fever and malaise (only half of acute infections cause symptoms)

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16
Q

Long term effects of chronic HBV infection?

A

Chronic active hepatitis
Cirrhosis
Hepatocellular carcinoma

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17
Q

What is HBsAg? What is it used for?

A

Hepatitis B surface antigen, used as diagnostic test for the virus as it is grossly over-produced

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18
Q

What is HBeAg?

A

E antigen is a soluble form of the core antigen of hepatitis B, the part of the virus that is inside the
surface antigen coat. And e antigen is important because it has a tolerogen effect

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19
Q

What is the toleragen effect of HBeAg?

A

The E antigen is a soluble form of the HBV core antigen

It can cross the placenta, causing teh foetus to recognise the e antigen as SELF.

Results in a clonal deletion of lymphocytes that recognise this antigen

Therefore, removes immune response to HBV and the baby gets a chronic infection

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20
Q

Chance of HBV being transmitted to baby if mother is +ve for HBsAg and not HBeAg?

A

<10%

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21
Q

Chance of HBV being transmitted to baby if mother is +ve for HBsAg AND HBeAg?

A

70-90% due to toleragen effect

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22
Q

What does HBsAg indicate?

A

Current infection

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23
Q

What does HB core antibody (IgG) indicate?

A

Past or present infection

if you’ve had Hep B, you’ll ALWAYS have IgG

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24
Q

What does HB core antigen (IgM) indicate

A

Infection in the past 6 months. Disappears after 6 months.

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25
Q

What does HB e antigen indicate?

A

HIGH INFECTIVITY and high grade infection.

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26
Q

What does anti-HbsAg indicate?

A

Immunity to infection (>10 MIU) either naturally or via vaccine

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27
Q

What does HBV DNA (quantitative) indicate?

A

Load test that determines response to treatment.

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28
Q

Difference between e antigen positive and e antigen negative infection?

A

e positive: very infectious and high grade, likely to develop chronic active hepatitis and HCC

e negative: low grade infection and low risk of transmission, not likely to develop symptoms. WILL MOST LIKELY HAVE e ANTIBODY PRESENT.

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29
Q

What vaccine is used for HBV?

A

Genetically modifed vaccine

Uses recombinent portein expressed in yeast and is the surface antigen protein

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30
Q

What groups are targeted for HBV vaccine in UK?

A

Neonates with HBV positive mums

Healthcare workers

Dialysis patients

Contacts of HBV cases

31
Q

What treatment options are there for HBV? (3)

A

Lamivudine (aim is suppression of the virus not cure)

Interferon (aim is cure of high grade infection)

Liver transplant

32
Q

What are the thernostic tests for HBV?

A

Lamivudine resistence

Viral load (HBV DNA)

33
Q

What cells are damaged by HCV?

A

Hepatocytes by BOTH direct viral effects and immune reaction

34
Q

How many genotypes does HCV have? Which ones are hard and easy to treat?

A

6 genotypes

Genotype 1 common in NI, poor response to treatment

Genotype 3, easier to treat

35
Q

What are the symptoms of HCV in acute phase?

A

Asymptomatic (only 10% get symptoms in acute stage)

36
Q

How many HCV cases become chronic?

A

70%!!

37
Q

Health effects of chronic HCV

A

50% chronic active hepatitis
20% cirrhosis (decades after infection)
Around 2% a year get HCC

38
Q

What does the HCV antibody indicate?

A

Past or present infection

39
Q

What does HCV RNA (by PCR) indicate?

A

CURRENT infection

40
Q

What does the HCV genotype marker indicate?

A

Guides treatment duration

Type 1=12 months
Type 3=6 months

41
Q

What does it mean if patient is HCV antibody positive but HCV PCR negative?

A

Past infection

42
Q

What does it mean if patient is HCV antibody positive and HCV PCR

A

Current infection

43
Q

Treatments for HCV? (3)

A

Ribavirin (aim is cure)

Interferon (aim is cure)

Transplant (but it recurs in nearly 100% of cases)

44
Q

What virus is treated with Ribavirn?

A

HCV

45
Q

What virus is treated with Lamivudine?

A

HBV

46
Q

What can theronostic assays be used for in HCV?

A

Genotype detection to guide treatment length

HCV RNA detection by PCR to guide response to treamtment

47
Q

Which cells are infected by HIV?

A

Retrovirus which affects immune cells:

CD4 lymphocytes (T helpers)
Macrophages
48
Q

Two main subtypes of HIV?

A

HIV1 (most cases) and HIV2

49
Q

How many cases of HIV in NI?

A

400 at the RVH

80 new cases a year

50
Q

What two diseases are caused by HIV?

A

Primary HIV infection

AIDS

51
Q

How long does it take to see a primary HIV infection post exposure?

A

10-25 days

52
Q

Symptoms of primary HIV infection?

A

Glandular fever, lymphadenopathy, rash

53
Q

Opportunistic infections in AIDS? (9)

A 
Retinitis
Encephalopathy
Lymphoma
TB
CNS infection
Bloody diarrhoea
Oesophageal infection
Pneumonia
Meningitis
54
Q

What opportunistic infection is caused by JC polyvirus?

A

Encephalopathy

55
Q

What opportunistic infection is caused by EBV?

A

Lymphoma

56
Q

What opportunistic infection is caused by Mycobacteria?

A

TB

57
Q

What opportunistic infection is caused by Toxoplasma?

A

CNS infection

58
Q

What opportunistic infection is caused by Cryptosporidia? (protozoa)

A

Bloody diarrhoea

59
Q

What opportunistic infection is caused by Candida?

A

Oesophageal infection

60
Q

What opportunistic infection is caused by pneumocystis? (fungi)

A

Pneumonia

61
Q

What opportunistic infection is caused by Cryptococcus? (fungi)

A

Meningitis

62
Q

What is the key test for HIV?

A

HIV antibody test

63
Q

What approach is used for HIV testing?

A

4 assay approach to reduce risk of false positive

64
Q

Therapy for HIV?

A

Anti-retroviral therapy (ART)

Aim is suppression not cure

65
Q

What 3 drug classes are used together to treat HIV?

A
  • Nucleoside reverse transcriptase inhibitors
  • Non-nucleoside reverse transcriptase inhibitors
  • Protease inhibitors
66
Q

How can vertical HIV transmission be prevented? (3)

A

C-section

Anti retroviral therapy to mother and baby

Avoid breast feeding

Reduces transmission from 16% to 1%

67
Q

3 theranostic assays used for HIV?

A

Viral load (response to treatment)

CD4 lymphocyte count (response to treatment)

Mutational analysis for drug resistance (sequencing viral genome)

68
Q

Which BBVs have vaccine?

A

HBV only

69
Q

Which BBVS have curative treatment?

A

HBV and HCV

70
Q

Which BBVs have suppressive treatments?

A

HBV and HIV

For HCV, aim is cure

71
Q

Post exposure prophylaxis for HBV?

A

Vaccine and IgG

72
Q

Post exposure prophylaxis for HIV?

A

ART drugs for 6 weeks

73
Q

Post-exposure prophylaxis for HCV?

A

None

74
Q

What is the window period in virus diagnostic testing?

A

Period in which patient is infected but no antibodies have developed yet- risk of false negative

SBCP Microbiology (9 decks)

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