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Medicine Year 1 - Semester 2 - Part 2 > Bloodborne Pathogens > Flashcards

Bloodborne Pathogens Flashcards

1
Q

What are blood borne infections ?

A

Infectious diseases caused by pathogenic micro-organisms which exist in blood and other bodily fluids.

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2
Q

What causes blood borne infections ?

A

Over 20 possible organisms (malaria, syphilis, brucellosis, VHFs etc.)

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3
Q

State some key viral pathogens

A

Hepatitis B (HBV)
Hepatitis C (HCV)
Human Immunodeficiency virus (HIV)

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4
Q

State some routes of transmission of blood-borne viruses

A

Blood-to-blood

Other bodily fluids

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5
Q

Blood-to-blood transmission causes

A

Injecting drug use
Needlestick & wound injury

Tattoos and piercing
Contaminated blood products

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6
Q

Bodily fluids transmission causes

A

Sexual & Genitourinary fluids (semen and vaginal secretions)

Birth canal (mother to child)

Other biological samples
- CSF
- Synovial / Pleural / Peritoneal fluid

Saliva / household utensils

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7
Q

Why are blood-borne viruses important ?

A

There is a risk of occupational transmission for healthcare workers (e.g. needle stick injury)

Often BBV infections are asymptomatic, BUT they can have serious long-term health consequences if not detected and managed.

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8
Q

Prevention of occupational exposure to BBVs

A

Standard universal precautions (wear gloves)

Disposal of sharps and hazardous waste

Hepatitis B vaccination

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9
Q

Management of any exposure to BBVs

A

Immediate 1st aid
Report and Test

Consider HIV post-exposure prophylaxis

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10
Q

What are viruses ?

A

Sub-microscopic infectious agents
- 80-1400nm diameter

Obligate intracellular parasites

Can be classified by nucleic acid content

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11
Q

Obligate intracellular parasites meaning

A

Rely on the metabolic processes of host cells

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12
Q

How are viruses identified ?

A

Identified based on:

  • protein antigens or antibodies to them
  • detection and amplification of nucleic acid (PCR)
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13
Q

Diagnostics for BBVs

A

Doing an antigen test - looking for presentation of protein

Look for antibodies of the protein

PCR testing - to amplify DNA / RNA

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14
Q

Main transmission of Hep B

A

Mother to child

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15
Q

Main transmission of Hep C

A

Blood to Blood contact

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16
Q

Main transmission of HIV

A

Sexual contact

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17
Q

Treatment of HBV - Hep B

A

Long-term anti-viral treatment can control chronic HBV infection

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18
Q

Treatment of HCV - Hep C

A

Anti-viral treatment
May clear (cure ?) HCV

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19
Q

Treatment of HIV

A

Anti-viral treatment can control chronic HIV infection

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20
Q

Vaccination / immunity for

  • HBV
  • HCV
  • HIV
A

HBV
- 95% of infected children/babies develop chronic HBV
- 95 of infected adults naturally clear HBV and are then immune
- there is an effective vaccine

HCV
- 20% of infected adults naturally clear, but are not immune
- no vaccine

HIV
- not cleared naturally
- no vaccine

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21
Q

Diagnosis for BBVs

A

Serology

HepB:
- HBV-DNA

HepC:
- HCV-RNA & genotype

HIV:
- Ag/Ab test, HIV-RNA

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22
Q

Global burden of disease - BBVs

A

Most common BBV - Hep B

Hep C - lowered numbers : more effective treatment

HIV

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23
Q

Why is there overlap between BBVs ?

A

As they are all transmitted in similar way.

So they cluster amongst population groups where risk of exposure occurs.

Some people get more than one BBV.

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24
Q

Hepatitis B: epidemiology

A

Most HBV transmission worldwide is from mother to child (during birth/early life)

This is preventable by vaccination.

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25
Statistics involving Hep B
296 million people living with HBV ~ 1.5 million new infections /year ~ 820,000 deaths/year 68% living in Western Pacific /Africa
26
Hepatitis B virology
HepaDNAvirus Hepatitis B can cause: - acute & chronic hepatitis - cirrhosis - heptocellular carcinoma
27
Describe the structure of a HBV viral particle
HBsAg - surface antigen HBcAg - core antigen HBeAg - circulates in the bloodstream DNA polymerase HBV DNA
28
Acute infection of HBV
Short duration Cleared within 6 months - asymptomatic - acute viral hepatitis - acute liver failure
29
Chronic infection of HBV
Long duration > 6 months infected - Chronic hep B - Cirrhosis : compensated - Cirrhosis : decompensated RISK OF HEPATOCELLULAR CARCINOMA
30
What does the outcome of Hep B depend on ?
Depends largely on age at the time of infection. Younger the age at infection : - greater the risk of chronic infection - lower the risk of being symptomatic during the initial phase
31
Hep B - infants
Most asymptomatic >90% progression to chronic infection
32
Hep B - >5years esp adults
More likely to have symptoms >90% clear acute infection
33
Acute Hepatitis B: Clinical Course
Incubation 6 weeks- 6 months Prodrome (few days) Icteric phase (<6 weeks) Convalescence (gradual recovery) OR Acute liver failure (<6 weeks)
34
Prodrome phase - acute hep B
few days - fatigue - fever - malaise
35
Icteric phase - acute hep B
< 6 weeks - jaundice
36
Acute liver failure
<6 weeks Encephalopathy Bleeding
37
Management of acute hep B
Anti-viral drugs and Transplantation in severe (fulminant) liver failure
38
Chronic Hepatitis B : Clinical Course
Immune tolerant phase Immune active phase Immune control phase Immune clearance phase Reactivation phase
39
What do symptoms and disease state of Chronic HBV depend on ?
The balance between HBV and host immune response.
40
HBsAg
Positive during acute and chronic infection
41
Anti sAb
Marker of immunity - positive following previous infection and vaccination
42
HBcAg
Not present in blood
43
Anti- HBc IgM
Positive during acute infection (sometimes in chronic flares)
44
Anti HBc IgG
Positive during chronic infection Positive during recovery
45
HBeAg
Positive during acute and some chronic infection; indicates high viral replication and transmissibility
46
Anti eAb
Often indicates reduced viral replication & transmissibility in chronic infection
47
HBV-DNA
- detection of virus Quantifies viral load
48
Hep B diagnosis
Only ~ 10% of people living with HepB worldwide are aware of their diagnosis
49
Describe antigens in Acute Hep B
For acute Hep B: The surface antigen goes up and comes down. The surface antibody goes up and stays up. The core antibody stays up.
50
Describe antigens in Chronic Hep B
For chronic Hep B: The surface antigen remains because you haven't cleared it. So, no surface antibody made really. Core antibody comes and stays. The e-antigen is initially positive but then becomes negative, as you move into the immune control phase
51
Treatment of acute hepatitis B
Usually no specific treatment Supportive care & avoid hepatotoxins Rarely antiviral drugs & transplantation in fulminant liver failure
52
Treatment of chronic hepatitis B
Anti-viral drugs may be used to reduce HBV-DNA & liver inflammation Tenofovir or entecavir are 1st line Often lifelong after initiation Aim to reduce the risk of cirrhosis and hepatocellular carcinoma.
53
Prevention of Hep B
Babies are vaccinated against Hep B @ 8,12 and 16 weeks
54
Reasons to vaccinate against Hep B
Uninfected household contacts Occupational or travel risk People who inject drugs Co-existing medical conditions
55
Hep C epidemiology
Globally ~58 million people have chronic HCV Most common in Eastern Mediterranean region.
56
Hepatitis C: Virology
Enveloped single stranded RNA virus Classified into genotypes 1-6 Rapid emergence of variants has prevented vaccine development
57
Describe the structure of Hepatitis C
Core Viral RNA Envelope glycoproteins Envelope
58
Why is there no vaccine for hep C ?
Rapid emergence of variance
59
Acute HCV
Resolved infection (~25%) Persistent infection (~75%)
60
Resolved HCV infection
Anti-HCV positive HCV RNA negative
61
Persistant HCV infection
Anti-HCV positive HCV RNA positive
62
Chronic HCV
Persistence of infection >6 months
63
Acute HCV
Usually asymptomatic Mild-non-specific symptoms Jaundice in ~15% of patients Serum ALT/AST may be high
64
Clinical course : HCV - Hep C
Infection persistent Chronic hepatitis with MILD fibrosis Chronic hepatitis with SEVERE fibrosis Liver cirrhosis (~20% in 20 years) Liver cirrhosis (decompensated) DEATH
65
HIV and HCV
HIV co-infection accelerates disease progression
66
Hepatitis C: diagnosis and severity assessment
Anti-HCV: current / past infection HCV-RNA: active infection Liver biopsy / fibroscan to stage disease
67
Treatment for Hepatitis C
Direct acting antivirals Highly effective new treatment Treatment duration is shorting Some regimens - now only 8 weeks Cure achieved in 95%
68
Hepatitis C : Prevention - for occupational reasons
There is no vaccine Safe handling of blood-contaminated materials Safe and appropriate use of healthcare injections Testing donated blood
69
Hepatitis C prevention
Harm reducing services for people who inject drugs Prevention of exposure to blood during sex Antiviral treatment of those who are infected
70
HIV epidemiology
2/3rd of cases African region 37 million people living with HIV
71
HIV: Virology
RNA-RT retrovirus Enters host immune cells (CD4 cells) Reverse Transcriptase action
72
Reverse transcriptase - HIV
Makes a DNA copy of the viral RNA Viral DNA is integrated into the host cell genome This pro-virus DNA is transcribed & translated into viral proteins Host immune cells are killed by invading virus, so the host becomes dangerously immune-suppressed.
73
HIV: what is necessary for cell entry ?
env gp120 env gp41
74
Enzymes involved in HIV
Reverse transcriptase Integrase Protease
75
HIV: function of reverse transcriptase
Drug Target Converts RNA --> DNA
76
HIV: function of integrase
Integrates viral DNA to host chromosome
77
HIV: function of protease
Helps process viral proteins
78
HIV: clinical course
Deterioration linked to loss of CD4 cells
79
Function of HIV diagnosis
Early HIV diagnosis can: - Save lives - Stop transmission
80
HIV diagnosis and severity assessment
Serology (HIV antibody detection) Antigen-Antibody tests HIV-Viral load CD4 count
81
Serology (HIV antibody detection)
Can be done in blood or oral fluid Available as rapid (& self-tests) Window period for seroconversion ~90 days
82
Antigen-Antibody tests - HIV
Done on blood (usually from a vein) 'Window' period ~18-45 days
83
HIV- Viral load CD4 count
Monitor treatment response and immune-suppression
84
What to do if the initial test is negative after exposure ?
Re-test at the end of the window period
85
HIV treatment : therapy
Anti-retroviral therapy (ART) is NOT curative but allows long healthy lives
86
HIV treatment : drugs
Typically give 3 drugs from more than 1 class: e.g. - 2 reverse transcriptase inhibitors (tenofovir, emtricitabine) - 1 integrase inhibitor (dolutegravir)
87
Describe ART
ART is lifelong one initiated Previously - "defer ART until low CD4 count" Now - early ART initiation improve long term outcomes
88
Reasons to be proactive in testing
Early ART initiation improves long term outcomes Reduction in sexual and vertical transmission of HIV Restore and preserve immunological function
89
HIV: reasons for prevention
Safer sex Often harm reduction Focus on testing
90
Uses of ART : Anti-retroviral therapy
Prevention of mother to child transmission U=U Pre-exposure prophylaxis Post-exposure prophylaxis
91
Key point about : HBV
Vaccine preventable
92
Key point about : HCV
NO vaccine but potentially curable
93
Key point about : HIV
No vaccine or cure Can be controlled by long-term medication

Medicine Year 1 - Semester 2 - Part 2 (53 decks)

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