1.5 Blood Borne Viral Infections

Question 1

What are the common blood-borne viruses?

Answer 1

Human Immunodeficiency Virus (HIV)

Acquired Immune Deficiency Syndrome (AIDS)

Question 2

What is the transmission routes for HIV?

Answer 2

Blood, semen, vaginal fluid

Present in saliva, but not infectious

Question 3

What does HIV infect?

Answer 3

Virus infecs CD4-T cells (lymphocytes)

Can also infect macrophage lineage

Question 4

What are the 2 types of HIV?

Answer 4

HIV-1 = easily transmissible, mostly in western countries

HIV-2 = less infectious, mainly West Africa

Question 5

How does HIV work?

Answer 5

1. Nucleocapsid envelope contains 2 ssRNA, reverse transcriptase-ribonuclease, proteases, and integrase
2. When virus pierces + fuses with CD4-T cell, injects cell with viral enzymes
3. Viral RNA + reverse transcriptase forms viral DNA + integrase
4. Viral DNA tansported across nucleaus of host chromosome and integrates into host DNA
5. Host DNA now produces more HIV cells (more viral RNA is released)

Question 6

What are the key differences in how HIV-1 and HIV-2 function?

Answer 6

HIV-1 = needs co-receptor CCR5/CXCR4 for entry

HIV-2 = less pathogenic + more promiscuous co-receptor usage

Question 7

What is hepatitis?

Answer 7

Inflammation of the liver

Question 8

What are the signs and symptoms of hepatitis?

Answer 8

1. Yellowing of skin and eyes
2. Dark urine
3. Light coloured stools
4. Nausea and vomiting
5. Loss of appetite
6. Extreme fatigue

Question 9

Hepatitis B has a highly efficient replication, reaching 1010 - 1012 virus/mL blood. But, what is the average incubation period for hep B

Answer 9

Avergae of 75 days, but can be up to 6 months

Question 10

Hepatitis B can survive for 1 week outsided the body and infects 2 billion worldwide, with 350 million chornic carriers (15-20%). What are the transmission routes for the virus?

Answer 10

Blood contact, vagina fluid, semen

No infections have been definitively documented via saliva

Question 11

Hepatitis C is a small, enveloped ssRNA virus. How does it replicate?

Answer 11

Uses host ribosomes to translate a long polypeptide chain that is processed into 10 different proteins

RNA polymerase replicates, other proteins mediate assembly of virus particles

Question 12

What is the transmission route for hepatitis C?

Answer 12

Blood contact

Question 13

What are some key differences between Hep B and Hep C?

Answer 13

Hep B = 25% of carriers die from liver disease or liver cancer

Hep C = 70% cases develop chronic liver disease

Hep C = 1000x lower in blood than Hep B

New antiviral meds = effective on Hep C

Question 14

What is the average infection risk after needlestick for Hep B+ ?

Answer 14

HBsAg and HBeAg+ = 22-31% clinical, 37-62% serological evidence

HBsAg and HBeAg- = 1-6% clinical, 23-37% serological evidence

Question 15

What is the averafe infection risk after a needlestick fot HCV+?

Answer 15

1.8% (0-7% range)

Question 16

What is the average infection risk after a needlestick for HIV+?

Answer 16

0.3% (0.2-0.5%)

Question 17

According to current Australian health care worker (HCW) regulations, HCWs MUST be tested tri-annually at a minimum for Hep B, Hep C, and HIV. Under what conditions must dental practitioners NOT perform exposure prone procedures?

Answer 17

1. HIV > 200 viral copies/mL blood
2. Hep C RNA +ve
3. Hep B DNA positive > 200 international units (IU)/mL blood

Question 18

What is the management procedure for a needlestick injury?

Answer 18

1. Wound management
2. Exposure reporting
3. Assessment of infection risk
4. Post-exposure prophylaxis
5. Status monitoring of exposed person at 6, 12, & 24 weeks

Question 19

What are the obligations for infected clinicians?

Answer 19

1. Not required to report +ve status to AHPRA or employer
2. All HCWs have professional obligation to learn about +ve staus and seeks formal advice
3. Can continue EPPs if viral load is below given thresholds