Bloodborne Pathogens Flashcards
What are different ways in which bloodborne pathogens can be 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. mosquitoes)
What is the difference between HIV and AIDS ?
HIV (=Human Immunodeficiency Virus) is the virus
AIDS (=Acquired Immunodeficiency Syndrome) is a condition
What area of the world is most affected by HIV ?
Sub-Saharan African
How many people worldwide are affected with HIV infection ? How many new cases were there in 2014 ?
37 Million
2.0 Million
What are the main transmission routes of HIV ?
– Via blood/blood products or contaminated needles
– Sexually (virus is present in semen and vaginal secretions)
– Perinatally (transplacentally during delivery, ingestion of breast milk)
What is the family and genus of HIV ?
Family: retroviridae
Genus: lentivirus
What are the subtypes of HIV ? Which is more common and which is more virulent ?
HIV-1 and HIV-2 pathogenic for humans
HIV-1 - most common and more virulent
What are the main morphological features of the HIV virus ?
- Spherical (80-100nm)
- Enveloped
- RNA genome
- Surface proteins, v antigenic (elicit strong immune response) including gp120
Why is RNA called a retrovirus ?
Because it uses reverse transcriptase to make DNA copy from viral RNA
What are the stages of replication of the HIV virus (including any major enzymes used for some steps) ?
- Virus binds to cell (HIV can only bind to CD4 positive T cell)
- Fuses with membrane of the cell
- Starts replicating its genome using machinery of host cell
- Makes DNA (reverse transcriptase)
- Can integrate viral DNA into host DNA (use integrase)
Describe the Time course of HIV infection with regards to viral load, CD4 cells, and Antibody to gp120.
Huge increase in viral load
Within 1 week, body makes antibody to gp120
Within 2 weeks, increase in CD4 T cells
As antibodies and CD4 T cells increase, viral load decreases
Without treatment or intervention, viral load starts going back up, CD4 cell count goes down
With therapy, viral load decreases and CD4 T cell count increases
Describe the progression from Exposure of HIV to AIDS ?
- Exposure to HIV
- Seroconversion
- Asymptomatic
- Persistent generalised lymphadenopathy
- AIDS-related clinical features
- AIDS
State some AIDS-defining conditions.
- Recurrent Pneumonia
- Invasive cervical carcinoma
- Kaposi’s Sarcoma
True or False: AIDS = HIV positive + one of these conditions or HIV positive + certain amount of CD4 T cells
True
Which percentage of people with
1. <1,500 copies
2. >55,000
of viral DNA/ml blood will develop AIDS within 9 years ?
- 13%
2. 93%
Describe treatment options for HIV infection.
MINIMISING VIRAL REPLICATION
1) Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
2) Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
3) Protease Inhibitors (PIs)
What is HAART ? What does the initial treatment usually contain ?
HIGHLY ACTIVE ANTI-RETROVIRAL THERAPY
Initial treatment often contain:
– 1 NRTI + 1 PI
or
– 2 NRTIs + 1 NNRTI
What are some ways to diagnose HIV ?
- DIAGNOSIS OF HIV SPECIFIC ANTIBODIES
- ELISA
- Western Blotting - VIRAL RNA DETECTION IN SERUM
- Nucleic Acid Amplification Test (including quantitative NAAT test to measure viral load)
Which steps of diagnosis must counselling be provided at ?
Before testing
Is there a vaccine available against HIV ?
No
Describe some of the morphological features of the Hepatitis B virus.
• Double-stranded DNA genome • Enveloped • 3 main antigen groups: E antigen (HBeAg) = pre-core antigen Surface antigen (HBsAg) Core antigen (HBcAg)
What is the family of the Hepatitis B virus ?
Family: Hepadnavirus
Differentiate between the different kinds of surface antigens in the Hep B virus ?
HBsAg:
– Indicates infectivity
– Anti-HBsAg provides immunity & appears late
HBcAg:
– Appears early in infection
HBeAg:
– Indicates high transmissibility
How is the HBV transmitted ?
- Blood or blood products
- Contaminated needles and equipment used by intravenous 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 infection of HBV ?
- Long incubation period - up to 6 months
- Development of acute hepatitis
- Possible development of chronic active hepatitis
Possible death (especially if fulminant disease)
What is the percentage of deaths due to fulminant hepatitis B ?
1-2 %
What is the percentage of Hep B patients develop chronic active hepatitis ?
50 %
Identify conditions associated with chronic active hepatitis B.
Cirrhosis
Hepatocellular carcinoma
Describe the progression in levels of the following, during acute Hep B infection.
- Surface antigens
- Core antigens
- Anti-HBc
- Anti-HBe
- Anti-HBs
INITIALLY:
Surface antigens and core antigens rise
THEN:
Anti-HBc (antibody to the core antigen) increase
Also, anti-HBe (antibody to the e antigen) increases
Also, anti-HBs (antibody to the s antigen) increases
Describe the progression in levels of the following, during chronic Hep B infection.
-Surface Antigens
Surface Antigens stays up the whole time due to lack of antibodies to it
What are the main clinical stages of Hep B ?
Pre-Icteric stage and Icteric stage
Describe the main clinical features in each of the main two clinical stages of Hep B.
PRE-ICTERIC STAGE: – Malaise – Anorexia – Nausea – Pain in right upper quadrant (tender liver)
ICTERIC STAGE:
– Jaundice
– Dark urine (bilirubin)
What parts of the body does jaundice affect ?
– Skin
– Sclerae
– Other mucous membranes
What is the cause of jaundice ?
hyperbilirubemia
What is the treatment for HBV ?
PEGYLATED INTERFERON OR ALPHA INTERFERON
-Suppress replication of virus (Pegylated is better at sustaining suppression of virus)
NUCLEOSIDE ANALOGUES (e.g. oral lamivudine)
- Have antiviral activity
- May be successful even in chronic patients
How may Hep B be prevented ?
- HBsAg vaccine (3 injections over 6 months)
- Blood screening
- Post-exposure prophylaxis: HBV immunoglobulin
- Needle exchange programmes
- Sexual health education
What proportion of non-A non-B cases of hepatitis were accounted for by Hepatitis C ?
Accounted for 90% of non-A non-B cases of hepatitis
Describe some of the morphological features of the Hepatitis C virus.
- Single-stranded RNA genome
* Enveloped
What is the family of the Hepatitis C virus ?
Flavivirus
Where does Hep C virus mostly replicate ?
In hepatocytes
Can the Hep C virus be cultured ?
No
Which kinds of cells does Hep C destroy ?
Liver cells
How is Hep C transmitted ?
- Blood and blood products
- Tattooing, body piercing and acupuncture
- Haemodialysis
- Sexual transmission uncommon
- Vertical transmission uncommon
What are the clinical features of Hep C virus ?
- Usually asymptomatic
- Fatigue
- Nausea
- Weight loss
- May rarely progresses to cirrhosis
- Small proportion may develop hepatocellular carcinoma
How is Hep C treated ?
INTERFERON
- Reduces liver transaminases in 80% of patients
- Ribavirin works well in combination with pegylated α-interferon
COMBINATION THERAPY -Often one of these in addition to ribavirin and pegylated α-interferon Sofosbuvir (nucleotide analogue) Boceprevir (protease inhibitor) Telaprivir (nucleotide analogue) Daclatasvir (inhibits NS5A)
Is there a vaccine for Hep C ?
No
How is HCV Screening achieved ?
-NAAT on blood samples
What area of the world is most affected by Malaria ? What percentage of Malaria cases does this area account for ?
Sub-Saharan Africa
80%
How many people worldwide are affected by Malaria ?
200 Million
What is the cause of malaria ?
5 species of the genus Plasmodium cause infection (Zoonotic disease) : – P. falciparum – P. vivax – P. ovale – P. malariae – P. knowlesi
Female Anopheles mosquito injects sporozoa into the bloodstream
Where does the malaria virus replicate ?
In the liver
What happens following replication of the malaria virus in the liver ?
The virus may become Hypnozoites (dormant form in the livere)
Virus may also become merozoites (active and infects RBCs and gets to the brain (cerebral malaria)
What are clinical features of malaria ?
• Fever
• Flu-like symptoms
• P. falciparum infection can rapidly progress to death
• P. falciparum affects every organ – wide range of complications e.g.
– Cerebral malaria
– Circulatory shock
– Hepatitis
How is malaria diagnosed ?
- At least 3 blood films (both thick and thin) obtained from different times for microscopy
- NAAT – useful for detecting drug resistance
How is Malaria treated ?
- Chemotherapy kills blood stages of parasite
- IF RESISTANCE, treatment advice should be changed regularly
-Combination therapy, including: – Quinine – Chloroquine – Doxycyclin – Proguanil – Malarone® (= proguanil + atovaquone) – Artemether
How is malaria prevented ?
- Sleep under bed nets
- Cover exposed skin between dusk and dawn
- Use of mosquito repellants
- Prophylaxis
- Vaccines currently being developed
What are preventative measures against HIV infection ?
- Screening of blood products
- Needle exchange programmes
- Anti-retroviral prophylaxis for needlestick injuries
- Avoiding high-risk sexual partners
- Use of barrier contraception
- Elective caesarian section
