Blood Borne Infections Flashcards
How do you calculate the risk of BBI transmission
Risk of BBI transmission = Risk that source is positive x risk per exposure.
If a source is positive what is the chance of a needle stick injury causing an infection for Hep B, C and HIV?
If source positive
Hep B – 1 in 3
Hep C – 1 in 30
HIV – 1 in 300
How should a needle-stick injury be managed at the time of injury>
Immediate action
Encourage bleeding and wash
Risk assessment by Occupational health
Assess risk of source being positive – risk factors, known, viral load, HBV vaccine?
Nature of exposure – hollow vs solid needles, gloves, skin puncture etc.
What post exposure prophylaxis should be offered to those who have a needle-stick injury where a patient was positive for a BBI?
Post exposure prophylaxis
• HIV – Triple anti-retroviral drugs for 28 days starting within 72 hours
• Hepatitis B – may need booster immunisation or immunoglobulins (if incompletely vaccinated or patient is HBsAg positive)
• Hepatitis C – no prophylaxis available
Who should be tested after a needlestick injury and what precautions should be taken by the recipient in the mean time?
Source patient – consent for HIV, HBsAg and HCV
Recipient – original blood sample stored – test at 4, 6, 12 and 24 weeks
Whilst waiting – safe sex, good infection control and avoid blood donations
What is HIV?
Virus that replicates and kills CD4 lymphocytes causing damage to the immune system over time if not controlled.
How is HIV transmitted?
Sexual
Blood and bodily fluids – IVDU, needlestick and transplant/transfusion
Vertical – during birth or breast feeding (rare due to HAART – both maternal and neonatal)
Increased risk of transmission if: high viral load, STI causing anogenital inflammation or breaks in skin or mucosa
Describe the presentation of seroconversion illness of HIV
Seroconversion = change from seronegative to seropositive i.e. production of antibodies
Fever and rash – very common Malaise Arthralgia and muscle aches Sore Throat Lymphadenopathy
How does symptomatic HIV present?
Weight loss
High temperature
Diarrhoea
Frequent opportunistic infections e.g. herpes zoster or candidiasis
What is AIDS?
Aids is defined as a CD4 count of less than 200 and or opportunistic infections
How should suspected HIV be investigated?
Combo assay (ELISA) detecting HIV antibodies and the p24 antigen
Confirmatory tests in lab if positive – immunoblot
RNA detection in the blood for viral load
Contact tracing very important
What are the AIDS defining conditions
TB Pneumocystis Cerebral toxoplasmosis Primary cerebral lymphoma Cryptococcal meningitis Progressive multifocal leucoencephalopathy Kaposi’s sarcoma* Persistent cryptosporidiosis Non-Hodgkin’s lymphoma* Cervical cancer* Cytomegalovirus retinitis
- = AIDS defining cancers
Wasting syndrome = loss of 10% body weight with fever over 30 days and chronic diarrhoea
How is HIV managed and what drugs does this involve?
HAART – highly active antiretroviral therapy – not a cure but viral load is undetectable
Excellent prognosis and risk of onward transmission is very small
HAART involves a number of classes of drugs:
• Nucleoside reverse transcriptase (NRTIs)
• Protease inhibitors (PIs)
• Non-nucleoside reverse transcriptase inhibitors (NRTIs)
• Integrase strand transfer inhibitors (InSTIs)
These are usually combined into one tablet taken daily. Compliance is very important and non-adherence can lead to resistance mutations.
What is hepatitis C?
RNA virus causing Hepatitis. No vaccine but treatable
Describe how Hep C presents?
Usually asymptomatic Jaundice Fatigue Nausea Fever Muscle aches
Incubation period of 6 weeks
20% clear the infection 80% progress to chronic infection – cirrhosis and hepatocellular carcinoma (1-5%)
How is Hep C transmitted?
IVDU Needlestick Transfusion and haemodialysis Vertical (5%) mode of delivery and breast feeding no impact Sexual transmission – very low
How should suspected Hep C be investigated?
Anti-HCV antibodies used for initial screening showing current or past infection
Positive 4-10 weeks after exposure (but offers incomplete protection allowing reinfection)
HCV RNA if Anti-HCV positive – distinguish current from past infection
LFTs – AST:ALT <1:1
Should always test for Hep A, B, C, D and E in any suspected hepatitis infection as well as CMV and Epstein Barr virus.
How should Hep C be managed?
No vaccine
Risk modification
Curable with anti-viral but reinfection possible
Consider HepB vaccine for baby with infected mother due to clustering of risk factors
What is Hep B?
Double stranded DNA virus causing chronic infection without a cure. Vaccine available
Describe the clinical features of Hep B?
Fever Urticaria Malaise Anorexia Nausea Arthralgia Jaundice Hepatosplenomegaly
How is Hep B transmitted?
Needlestick IVDU Transfusion (unscreened) Tattoos Renal dialysis in high-risk endemic countries Sexual Vertical
How does Hep B progress?
Childhood infection – 10% spontaneously clear the virus
90% develop chronic infection leading to non-replicative cancer or chronic hepatitis. 40% develop cirrhosis
Adult infection – 99% develop acute hepatitis whilst less than 1% develop severe hepatic failure. 95% of those with acute infection will clear it. 5% develop chronic infection leading to non-replicative cancer or chronic hepatitis. 20% of those with chronic hepatitis will develop cirrhosis.
Acute infection = less than 6 months
Chronic infection = more than 6 months
How should Hep B be investigated?
LFTs – very high in acute infection marginally high in carrier
Blood tests for serology
Surface antigen and antibody
Core antigen and antibody
Hep B e antigen (doesn’t last as long indicates acute vs chronic)
Surface antigen = current active infection IgM if acute IgG if chronic
Surface antibody = immune to Hep B infection or vaccinated
Core antibody = previous exposure to hepatitis B
Should always test for Hep A, B, C, D and E in any suspected hepatitis infection as well as CMV and Epstein Barr virus.
What steps can be taken to reduce the risk of Hep B infection transmission?
Hep B positive cannot donate blood/organs/semen
Do not share needles
Condom use
Do not share razors or toothbrushes
How should Hep B be managed?
No treatment other than vaccination
Sexual contacts tracing
Vaccination
HBIG if recent (within 7 days)
Use condoms/dental dams until immune
