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HBV Flashcards

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1
Q

Outline the chain of infection

A
  • infectious agent
  • reservoir
  • portal of exit
  • means of transmission
  • portal of entry
  • susceptible host
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2
Q

What is the infectious agent in hepatitis B?

A

hepatitis B virus (HBV)

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3
Q

Describe the HBV infectious agent

A

partially double-stranded DNA virus

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4
Q

What family does HBV belong to?

A

Hepadnaviridae

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5
Q

How infectious is HBV?

A

highly infectious (1 in 3 / 30%)

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6
Q

How does the infectivity of HBV compare to HIV?

A

HBV is up to 100x more infectious than HIV (1 in 300 / 0.3%)

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7
Q

How stable is HBV?

A

remarkably stable - can survive over 7 days on environmental surfaces

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8
Q

How long can HBV survive on environmental surfaces?

A

> / 7 days

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9
Q

Where can HBV be detected?

A

HBV present in high titres in blood and detectable in several body fluids

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10
Q

What are the 2 main types of HBV particle?

A

Dane particle (intact viron) and subviral particle (incompletely assembled viron particles containing hep B surface antigen)

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11
Q

What is serology?

A

study of serum and other bodily fluids, mainly focusing on the presence of antibodies in the serum

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12
Q

Why is HBV serology important in dentistry?

A

dental professionals are at occupation risk of HBV due to regular exposure to blood and blood-contaminated saliva

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13
Q

What reasons is understanding HBV serology essential for?

A
  • assessing patient infectivity
  • managing exposure incidents (needlestick injuries)
  • confirming vaccine response and immunity
  • meeting UK occupational health clearance requirements (GDC)
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14
Q

What is the first antibody to be produced following primary antigen exposure?

A

IgM (peaks around day 13)

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15
Q

What is the second antibody to be produced following primary antigen exposure?

A

IgG (larger peak than IgM, around day 20)

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16
Q

Describe the structure of HBV from outside to inside

A
  • HBsAg (surface antigen)
  • HBeAg (E antigen)
  • HBcAg (core antigen)
  • DNA
  • DNA polymerase
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17
Q

What is HBsAg?

A

hepatitis B surface antigen

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18
Q

What does it mean if a patient has HBsAg in their serum?

A

current HBV infection (acute or chronic) - patient is infectious

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19
Q

How can you identify whether a patient has an acute or chronic HBV infection using serology?

A

would need to take serial blood samples - if HBsAg present >6 month this is a chronic infection

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20
Q

What is the dental relevance of a patient with a current HBV infection (HbsAg)?

A
  • no restriction on routine dental care (standard precautions)
  • heightened importance of sharps safety and exposure management
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21
Q

What is the anti-HBs?

A

hepatitis B surface antibody

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22
Q

What does it mean if anti-HBs is present in the serum?

A

immunity to HBV

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23
Q

How can anti-HBs be developed?

A
  • after successful vaccination
  • after recovery from a natural infection
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24
Q

What are the UK occupational-health thresholds for anti-HBs?

A

> / 10 mIU/mL is evidence of protection
/ 100mIU/mL correlates to an adequate response

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25
Which anti-HBs threshold is preferred for healthcare workers?
>/ 100 mIU/mL
26
What is the dental relevance of anti-HBs?
- required for dental students and clinical staff - documented anti-HBs is essential for clinical clearance
27
What is the anti-HBc?
Hepatitis B core antibody
28
What does it mean if anti-HBc is present (positive) in the serum?
previous exposure to HBV (past or current natural infection)
29
How can anti-HBc be produced?
by past / current natural infection, NOT by vaccination
30
What is the dental relevance of anti-HBc?
- helps distinguish vaccinated individuals from those with past infection - important when assessing unclear serology
31
How can people who have been vaccinated against HBV be distinguished from those who've had a natural infection?
anti-HBc will be present in the serum of those who've had a natural infection, but not present in vaccinated individuals
32
What does it mean if IgM anti-HBc is present in the serum?
recent (acute) infection
33
When is IgM anti-HBc present in the serum?
early in the infection, before anti-HBs develop
34
What is the dental relevance of IgM anti-HBc?
- indicates high infectivity - mainly relevant in hospital or oral-surgery settings rather than routine screening
35
What is HBeAg?
Hepatitis B e antigen (under surface)
36
What does it mean if HBeAg is present in the serum?
high viral replication and high infectivity
37
Where does the HBV replicate?
liver
38
What is the dental relevance of the HBeAg?
historically used to assess transmission risk (HBeAg +ve indicated high transmission risk)
39
Which test now supplements / replaced HBeAg for assessing transmission risk?
HBV DNA viral load (in plasma)
40
What is anti-HBe?
Hepatitis B e antibody
41
What does it mean if anti-HBe is present in the serum?
reduced viral replication
42
What is the dental relevance of anti-HBe present in the serum?
suggests lower infectivity, but standard infection control measures remain unchanged
43
Out of HBsAg, anti-HBs and anti-HBc, which are present in a vaccinated individual?
anti-HBs
44
Out of HBsAg, anti-HBs and anti-HBc, which are present in an individual with an acute infection?
HBsAg, anti-HBc (IgM)
45
Out of HBsAg, anti-HBs and anti-HBc, which are present in an individual with a chronic infection?
HBsAg, anti-HBc (IgM)
46
Out of HBsAg, anti-HBs and anti-HBc, which are present in an individual recovered from a past infection?
anti-HBs, anti-HBc
47
What are the UK dental requirements on HBV?
- HBV vaccine is mandatory - post-vaccine serology required to confirm response - non-responders may require additional vaccine dose / specialist advice
48
What conditions are you required to disclose to the GDC?
presence of any infectious disease, blood-borne virus (HIV, HBV, HCV) or other transmissible disease
49
How is the response to the HBV vaccine confirmed?
post-vaccination serology testing
50
What is the relevance of HBV-positive patients?
- must not be refused care (may not be aware of infection) - standard IP+C measures sufficient - immediate reporting and risk assessment of all sharps injuries
51
What is the reservoir for HBV?
humans are the only reservoir
52
Which patients are a HBV reservoir?
patients with acute HBV infection, patients with chronic HBV infection (often asymptomatic and undiagnosed)
53
What is a major source of HBV transmission worldwide?
chronic carriers
54
Why are chronic carriers of HBV a major source of transmission?
they are often asymptomatic and undiagnosed
55
What is the dental relevance of the HBV reservoir (humans)?
patient's HBV status may be unknown - standard precautions must be applied to all
56
How many people worldwide were living with chronic hepatitis B infection in 2022?
254 million people
57
How many new HBV infections are there each year?
1.2 million new infections each year
58
How many deaths from HBV occurred in 2022?
1.1 million deaths
59
What are the major causes of deaths from HBV?
cirrhosis and hepatocellular carcinoma (primary liver cancer)
60
How did the COVID-19 pandemic impact HBV?
impacted delivery of HBV prevention, testing / diagnosis and treatment in Scotland. But now recovering
61
Which year was the highest total of newly diagnosed acute or chronic HBV infection in Scotland
2023 (518 new diagnoses) was the highest since 2014 (456) - impact of COVID-19
62
What was revealed in the 2024 report on Hepatitis B in London?
there were 3882 new lab reports of HBV in London (population of 9 million)
63
How much did new lab reports of HBV increase by between 2021 and 2022 in London?
42.4%
64
What population groups were the highest number of new HBV lab reports in (most prevalent)?
35-44 males and females
65
What is the HBV portal of exit?
blood, blood-contaminated bodily fluids including saliva and gingival crevicular fluid (GCF)
66
Which bodily fluid has the highest viral concentration?
blood
67
What is the dental relevance of the portal of exit of HBV?
blood-stained saliva during extractions, periodontal therapy, endodontics and oral surgery is a concern
68
How does transmission of HBV occur?
through percutaneous or mucosal exposure to infectious blood or body fluids
69
What is the most common mode of transmission of HBV in endemic areas?
- perinatal transmission (from mother to child at birth) - horizontal transmission (especially between infected children <5 yo)
70
When are 95% of chronic HBV patients infected?
infants infected from their mothers (perinatal transmission) or before 5 years old (horizontal transmission)
71
Aside from perinatal transmission or horizontal transmission, what is the other main route of HBV transmission?
sexual transmission (unprotected vaginal or anal intercourse)
72
How can percutaneous exposure to HBV occur in dentistry?
- needlestick / sharps injury - cuts from dental instruments
73
How can mucosal exposure to HBV occur?
splash to eyes, nose or mouth
74
How can indirect transmission of HBV occur in dentistry?
contact with contaminated instruments or surfaces if decontamination fails
75
What is the dental relevance of the HBV mode of transmission (percutaneous, mucosal exposure, indirect)?
sharps handling, PPE, instrument reprocessing (automated washer disinfector instead of manually - reduces risk of percutaneous exposure), surface cleaning are critical control points
76
How can HBV NOT be transmitted?
casual contact, aerosols alone, intact skin
77
What were HBV transmissions from dentists to patients in 1970s-80s associated with?
- unrecognised chronic HBV infection of clinician - blood contamination during invasive procedures - inadequate glove use / perforation
78
How was the genetic identity between the clinician and patient HBV strains confirmed?
molecular epidemiology later confirmed the genetic identity
79
What do the outbreaks in 1970-80s of HBV-infected dentists transmitting HBV to patients demonstrate?
- potential for transmission - highly infectious nature of HBV
80
How has dentistry changed to largely eliminate the risk of HBV transmission?
modern controls like universal glove wearing, HBV vaccination of dental professionals
81
How can HBV transmission via instruments occur?
inadequately cleaned / sterilised instruments, blood contamination remained within lumens / hinged instruments (difficult to clean)
82
What fields of dentistry have an increased risk of HBV transmission via instruments?
- oral surgery - periodontal surgery - extractions - endodontics
83
Why is robust decontamination essential to prevent transmission of HBV especially?
HBV can survive on surfaces for >/ 7 days
84
How can patient-to-patient HBV transmission occur without infection of the clinician?
cross-contamination via contaminated environment / instruments
85
How can HBV be transmitted from patient to dental professional?
- needlestick / sharps injury - cuts from contaminated instruments - blood splashes to mucous membranes
86
Why is oral surgery at a higher risk of HBV transmission compared to routine dentistry?
- greater blood loss - use of scalpels, wires, powered instruments (increased sharps risk) - longer procedures (increased exposure time)
87
What is the HBV transmission risk after a percutaneous injury from an HBeAg-positive (high viral replication and infectivity) source?
up to 30% (100 times greater risk than HIV)
88
What are the hierarchy of controls?
elimination, substitution, engineering control, administrative controls, PPE
89
Why is modern transmission of HBV now rare?
- universal HBV vaccination of dental professionals - standard precautions (gloves, eye protection) - improved sterilisation and surface disinfection - safer sharps, reduced recapping - clear policies for exposure-prone procedures - post-exposure prophylaxis (PEP) available if required
90
What are the possible portal of entries for HBV?
- broken skin - mucous membranes (genital mucosa, oral mucosa, conjunctiva) - perinatal exposure during delivery
91
What is the dental relevance of the portal of entry for HBV?
unprotected, eyes, mouth, or damaged skin increase occupational risk (importance of PPE - gloves, eye protection, masks)
92
Apart from dentistry, what is another field where HBV outbreaks can result from inappropriate infection control?
tattooing
93
What factors influence susceptibility to HBV?
- lack of immunity (unvaccinated) - age at infection - occupational exposure (healthcare workers)
94
What is the risk of neonates acquiring chronic HBV infection following exposure?
~90% risk of chronic infection in neonates
95
What is the risk of children developing a chronic HBV infection?
~30% risk of chronic infection in children
96
What is the risk of adults acquiring a chronic HBV infection following exposure?
<5% risk of chronic infection in adults
97
How does the HBV vaccine protect the host against HBV?
vaccine induces production of anti-HBs (Hepatitis B surface antibodies)
98
What is the dental relevance of susceptible hosts?
- HBV vaccine mandatory for dental professionals - post-vaccine antibody testing required to confirm protection
99
How does acute HBV infection present in children?
often asymptomatic or mild
100
What presentations may symptomatic adults with an acute HBV infection develop?
- jaundice - malaise - elevated ALT (liver enzyme)
101
What is fulminant hepatitis?
a rare and severe form of liver failure (can result from HBV)
102
How rare is fulminant hepatitis?
<1% of HBV cases
103
What is recovery from an acute HBV infection characterised by?
- clearance of HBsAg - development of anti-HBs
104
How long does immunity following a cleared acute HBV infection last?
lifelong immunity
105
How is chronic HBV infection defined?
HBsAg persistence for >6 months
106
What does the risk of developing a chronic HBV infection strongly depend on?
age at infection (90% risk in neonates, 30% in children, 5% adults)
107
How do patients with a chronic HBV infection present?
may remain asymptomatic for decades (major transmission). Possible development of long-term complications
108
What are possible long-term complications that may develop from chronic inflammation due to chronic HBV infection?
- cirrhosis - liver failure - hepatocellular carcinoma
109
How can the chain of HBV infection be broken in general population (not just within dentistry)?
- universal HBV vaccination - standard precautions in healthcare (gloves, sharps safety) - screening for blood products - post exposure prophylaxis - safe injection (IVDU) and sexual practices - safe tattooing practices
110
What does post-exposure prophylaxis of HBV consist of?
HBV vaccine with/without hepatitis B immunoglobulin
111
What are the 2 classes of products available for protection against HBV?
vaccine and a specific immunoglobulin (HBIG)
112
What is the role of the HBV vaccine?
confers active immunity
113
What is the role of the specific immunoglobulin, HBIG?
provides passive and temporary immunity while awaiting response to vaccine
114
What do most HBV vaccines contain?
HBsAg (antigen) - do not contain live organisms, do not cause HBV
115
How is the HBsAg in HBV prepared?
using recombinant DNA technology from yeast cells
116
Hepatitis B vaccine is highly effective at preventing infection if given shortly after the exposure. How fast should immunisation be delivered ideally?
ideally commence immunisation within 24hrs of exposure
117
Are reinforcing doses required for those who have received pre-exposure immunisation?
WHO states there is no compelling evidence for the requirement of a booster dose
118
How long does the hepatitis B vaccine offer protection?
full duration of protection is yet to be established. WHO concludes protection against chronic infection persists for 20-30 years or more
119
What percent of adults response adequately to the hepatitis B vaccine?
90%
120
How soon after the primary course of the vaccine should anti-HBs titres be checked for healthcare workers (at risk of occupation exposure)?
1-2 months after primary course of vaccine
121
What may non-responders to the HepB vaccine (anti-HBs <10mIU/ml) require?
follow up and additional precautions following a significant sharps injury
122
Although anti-HBs levels above 100mIU/ml are preferred, what level of immunity is generally accepted as enough to protect against infection?
>/ 10 mIU/ml are generally accepted as enough to protect
123
What is required from responders with anti-HBs levels between 10 and 100 mIU/ml?
one additional dose of vaccine
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