Bloodborne Pathogens Flashcards
How are bloodborne pathogens transmitted?
- Direct contact with infected blood fluids.
- Infection via contaminated needles, syringes, or other unsterilised instruments.
- Direct infection into the bloodstream by arthropod vectors (e.g. mosquitos).
How is HIV transmitted?
- Occurs by 3 routes:
- Via blood / blood products or contaminated needles.
- Sexually (virus is present in semen and vaginal secretions).
- Perinatally (transplacentally during delivery, ingestion of breast milk).
Describe the classification of HIV.
- Family - retroviridae
- Genus - lentivirus
- HIV-1 and HIV-2 pathogenic for humans
- HIV-1 is most common
- HIV-2 is less virulent
Describe the viral features of HIV.
- Spherical (80-100nm)
- Enveloped
- RNA genome
- Retrovirus - uses reverse transcriptase to make DNA copy from viral RNA.
Describe the time course of HIV infection.
Describe the progression of HIV to AIDS.
- Exposure to HIV
- Seroconversion
- Asymptomatic
- Persistent generalised lymphadenopathy
- AIDS-related clinical features
- AIDS
What are the defining conditions associated with AIDS?
How does the viral load of HIV affect the development of AIDS?
-
Viral RNA copy number (viral load) in blood:
- 13% of those with <1,500 copies/mL blood will develop AIDS within 9 years.
- 93% of those with >55,000 copies/mL blood will develop AIDS within 9 years.
What are the available drugs for the treatment of HIV?
-
Anti-retroviral therapy (ART):
- Nucleoside reverse transcriptase inhibitors (NRTIs).
- Non-nucleoside reverse transcriptase inhibitors (NNRITs).
- Protease inhibitors (PIs).
- There are many possible regimens and combinations.
- Initial treatment often contains:
- 1 NRTI + 1 PI
- OR
- 2 NRTIs + 1 NNRTI
Describe the diagnosis of HIV infection.
- Diagnosis of HIV specific antibodies.
- ELISA
- Western Blotting
- NAAT used to detect viral RNA in serum.
- Quantitative NAAT used to measure viral load.
- Individual testing must be preceded by counselling.
- An initial negative result should always be followed-up.
Describe the prevention of HIV infection.
- No vaccine yet available
- Screening of blood products
- Needle exchane programmes
- Anti-retroviral prophylaxis for needlestick injuries
- Avoiding high-risk sexual partners
- Use of barrier contraception
- Elective caesarian section
Describe the viral features of hepatitis B (HBV).
- Hepadnavirus
- Double-stranded DNA genoma
- Enveloped
What are the antigens associated with hepatitis B virus (HBV)?
- HBsAg - surface antigen
- Indicated infectivity
- Anti-HBsAg provides immunity and appears late
- HBcAg - core antigen
- Appears early in infection
- HBeAg - pre-core antigen
- Indicates high transmissibility
How is HBV transmitted?
- Via blood or blood products.
- Contaminated needles and equipment used by IV drug users.
- Association with tattooing, body piercing and acupuncture.
- Sexual intercourse
- Intra-uterine, peri- and post- natal infection.
- Contaminated haemodialysis equipment.
What are the stages of HBV infection?
- Long incubation period - up to 6 months.
- Development of acute hepatitis.
- Fulminant disease carries 1-2% mortality rate.
- 50% of patients develop chronic active hepatitis.
- Cirrhosis
- Hepatocellular carcinoma
Describe the development of an acute HBV infection which is self-limited.
Describe the development of a chronic HBV infection which is persistent.
What are the viral features of hepatitis C virus (HCV)?
- Flavivirus
- Single-stranded RNA genome
- Enveloped
- Replicated primarily in hepatocytes
- Destroys liver cells
- Virus cannot be cultured
What are the clinical features of HCV?
- Usually asymptomatic
- Fatigue
- Nausea
- Weight loss
- May rarely progress to cirrhosis
- Small proportion may develop hepatocellular carcinoma
What is the cause of malaria?
- Caused by 5 species of the genus Plasmodium
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
- Female Anopheles mosquito injects sporozoa into the blood stream.
- Zoonotic disease.
