Bloodborne Viruses

Question 1

What is the pathogenesis of HIV infection?

Answer 1

1) virus binds cd4 receptors and coreceptors (CCR5/CXCR4)
2) virus penetrates cell
3) contents empty
4) RNA converted to DNA (reverse transcriptase outside of nucleus)
5) viral DNA integrated into DNA (integrase)
6) transcription and translation so viral proteins are made
7) viral proteins assemble within cell e.g. antigens
8) viral proteins leave cell (go on to infect other cells)
9) cell membrane ruptures and kills cell

Question 2

What are the stages of HIV?

Answer 2

Primary is asymptomatic with normal or small/temporary drop in CD4

Stage 1 is asymptomatic with CD4 count above 500

Stage 2 is mild symptoms with CD4 count below 500

Stage 3 is advanced symptoms and CD4 count below 350

Stage 4 is severe symptoms and CD4 count less than 200 (AIDs defining)

Question 3

What are symptoms of HIV?

Answer 3

• fever
• weight loss
• pharyngitis
• headache
• malaise
• myalgia
• splenomegaly
• nausea
• vomiting

it becomes AIDs defining with infection with TB, toxoplasmosis, PCP, candida infection or Human herpes b.

Question 4

How is HIV transmitted?

Answer 4

sexual, needle stick, vertical, in utero

risk depends on factors such as viral level, other STIs condon use etc.

Question 5

What is the prognosis for HIV?

Answer 5

very good with early diagnosis and treatment

Question 6

How is the diagnosis of HIV made?

Answer 6

blood test for HIV antigen and antibody (only positive after 4-6 weeks of infection so may get false negative)

rapid tests such as saliva or fingerpick. accurate to rule out but lots of false positives.

high risk people should be tested e.g. pneumonia, sti, dementia, unexplained weight loss, fever.

Question 7

What is the treatment for HIV?

Answer 7

2 NRTIs and 1 NNRTI, protease inhibitor or integrase inhibitor. Aim is to produce an undetectable viral load, with low transmission risk and a reconstituted immune system.

Question 8

How is hepatitis B transmitted?

Answer 8

vertical transmission
IVDU
sexually
needle stick injuries in healthcare workers

Question 9

What are acute hepatitis b symptoms?

Answer 9

• jaundice
• fatigue
• abdominal pain
• nausea
• vomiting
• arthralgia
• can be asymptomatic or vague

6% of patients become chronic

Question 10

What are clinical signs of hepatitis B?

Answer 10

massively raised ALT/AST

Question 11

Describe the serology findings in hepatitis B

Answer 11

1. Surface antigen presents first
2. E-antigen presents in infectious stage (HbeAg)
3. Core antibody – HBcAb=IgM
4. E-antibody – HbeAb – e-antigen gone and so no longer infectious
5. Surface antibody – HbsAb – virus cleared
6. Core antibody persists for life – HbcAb IgG

the Hep B vaccine is genetically engineered surface antigen to develop immunity.

Question 12

What are the complications of chronic hepatitis B?

Answer 12

if virus persists after 6 months, hepatitis is chronic. the viral dna integrates. 25% of patients develop liver cirrhosis and 5% develop hepatocellular carcinoma.

life long antivirals are required to suppress replication (not required for inactive carriers)

Question 13

How is Hepatitis C transmitted?

Answer 13

same ways as B, but risk of transmission through needlestick injury is even higher

Question 14

What are the symptoms of hepatitis C?

Answer 14

• 80% are asymptomatic
• fatigue
• dyspnoea
• dark urine
• nausea
• chronic hepatitis and chronic liver disease

no vaccine but treatment of antiviral drug for 8-12 weeks. there remains a chance of reinfection.