MB13 Sexually Transmitted Infections - BBVs Flashcards Preview

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What are the key blood-bourne viruses and what do they cause?

  • (HBV) Hepatitis B Virus - Hepatitis 
  • (HBC)Hepatitis C Virus - Hepatitis
  • (HIV) Human Immunodeficiency Virus - AIDs and HIV seroconversion illness


Discuss the Taxonomic status of the blood bourne viruses?



What do the viruses have in common, what does this meam?

HBV - Hepadnavirus - DNA

HCV - Flavivirus - RNA

HIV - Retrovirus:Lentivirus - RNA 


All the viruses are enveloped, this means that they are LABILE

They do not survive well in the environment


What are the three routes of transmission of BBVs?




What is significant about the shared modes of transmission?

  1. Penetrative sexual intercourse (HIV)
  2. Contaminated blood (including medical procedure, transfusion, needle sharing associated with IV drug use and tattoos) (HCV)
  3. Vertical (including breast feeding) (HBV


If a patient has contracted one BBV then they

should be considered at risk for others.


What is the preferred route of transmission for HBV?

Vertical (including breastfeeding)


What is the preferred route of transmission for HCV?

Contaminated blood (including medical procedure, transfusion, needle sharing associated with IV drug use and tattoos) 


What is the preferred route of transmission for HIV?

Penetrative sexual intercourse


What family is HBV from?

Hepadnavirus Family


HBsAg particles on surface - surface antigen can be tested for

Whole virus is called 'Dane Particle'



  1. What is the pathogenesis and clinical course of HBV?
  2. What is the incubation period?

  1. Not directly cytopathic for liver cells, and the pathology is largely immune mediated (virus-specific cytotoxic T cells)
  2. The incubation period ranges from 6 weeks to 6 months, 2.5 months typical timing - But lab test for HBsAg will be positive before this.

•Clinical signs of hepatitis 



What is the likelihood of becoming a carrier (persistent or chronic infection)?


When is it more likely to become a carrier?

  • marked age-related effect:

90-95% of perinatally infected infants became carriers 23% of those infected at 1-3 years of age, 3% of those infected as university students

  • more likely in the immunosuppressed, and in males 



What are the consequences of chronic hepatitis?

  • Cirrhosis - This is an irreversible form of liver injury when liver is replaced by scar tissue.
  • Hepatocellular carcinoma
    • one of the 10 most common cancers worldwide.
    • Hepatitis B carriers are 200 times more likely to develop liver cancer.
    • 20-30 years after the infection. 


How is HBV transmitted?

What is the main form of transmission?  (in bold)


What reduces the incidence of these transmission events?

  • Sexual intercourse
  • Vertical mother to child (intrauterine, peri- and postnatal infection.
  • Blood
    • e.g. blood contaminated needles/equipment shared by injecting drug users
    • tattooing, body-piercing and acupuncture
      • due to reusing needles
    • healthcare settings such as renal units
      • blood contaminated hemodialysis equipment.
    • HBV transmission from hepatitis B carrier healthcare workers (HCWs) to their patients while carrying out exposure-prone procedures. And from patients to HCW via needle stick injuries

Hepatitis B immunization and HBsAg screening of HCWs 


HBV Epidemiology


Which country has the greatest carrier prevalence?

How many people are infected worldwide?

Southeast Asia, sub-Saharan Africa and China (20%)

350 million


(North, West and Central Europe, North America and Australia

•0.5% in,

–East Europe & Mediterran

• 0.7%, )


How is HBV diagnosed?

What do each of these indicate..

  1. HBsAg
  2. HBeAg
  3. HB core IgM
  4. Anti-HBsAg
  5. What is a good measure of immunity?


If positive, person has HBV, if negative, don't

  1. Currently Infected
  2. High grade infection
  3. Recent Infection
  4. Immunity
  5. –>100 mIU/ml is good evidence of immunity


What is the treatment for HBV?

  • oral antiviral therapy (supression therapy)

Tenofovir (Lamivudine is not used anymore)

(Lamivudine in past - resistance may develop, not used anymore)

  • interferon (immunomodulator effect) - improved regimens recently. Pegylated interferon


HBV vaccine

  1. What is it made up of?
  2. How many doses?
  3. Who is immunisation recommended for?
  4. What proportion fail to produce the protective HB surface antibody?
  5. When healthcare workers are being tested for response to vaccine, what is considered a good response?

  1. genetically engineered HBsAg produced in yeast

  2. Three doses (good protection in over 90% of healthy adults)

  3. •dialysis patients (& similar groups)

    •all health care workers,

    •sexual contacts of individuals with acute or chronic HBV

    •injecting drug users. 

  4. 10%

  5. >100iu/ml


  1. What is the risk of mother to baby transmission?
  2. How can this be prevented?

  1. E antigen positive mothers have 95% chance of transmission to baby
  2. Can be prevented using Vaccine and immunoglobulin (Human blood product)
    1. All pregnant women in UK are screened for carriage


  1. What family is HCV from?
  2. How many genotypes of HCV are there?
  3. Which genotype is associated with poor response to treatment?
  4. Which genotype is associated with good response to treatment?

  1. Flavirus Family (single-stranded RNA virus)
  2. Six
  3. Genotype 1
  4. Genotype 3



  1. What is the incubation period?
  2. What is the norm in the acute phase?
  3. What percentage of HCV infected individuals will develop chronic HCV?
  4. How is the virus detectable in chronic HCV?

  1. 2-4 months
  2. Subclinical infection (mild disease in 10%)
  3. 75%
  4. In the blood (PCR)
    1. –15% progress to cirrhosis within  20 years,

      –1% per year risk of liver cancer in those with established cirrhosis.

      –May require liver transplantation - leading reason for liver transplants


HCV Epidemiology

  1. How many people are infected worldwide?
  2. What was it the leading cause of?
  3. What is the gap between infection and significant disease?

  1. 170million
  2. transfusion associated hepatitis (until screening tests introduced in 1991)
  3. Long gap (decades)


How is HCV transmitted?

Preferred transmission route in bold

  • Blood
    • blood products, contaminated needles shared by injecting drug users,
    • tattooing, body-piercing and acupuncture, (reusing needles).
    • healthcare settings such as renal units
      • (HCV monitoring of patients)
    • HCV transmission from HCV carrier HCWs carrying out exposure-prone procedures on their patients,
      • E.g. needlestick injuries resulting in blood-to-blood contact during cardiothoracic surgery.


  • Vertical Trasmission - uncommon (unlike HBV) 
  • Sexual transmission - uncommon. 


How is HCV Diagnosed?





What are the implications of this?

  • Serological assays to detect HCV antibody
    • EIA, RIBA
  • qualitative and quantitative HCV RNA detection methods 
  • genotype analysis 

(HCV RNA is present in approximately 70% of individuals with HCV antibody.)

If positive serology = have had in past. Are they currently infected? Then PCR to determine. 

All blood donors are screened for HCV & HIV and HBV




HCV Treatment

  1. What is the treatment?
  2. What new drugs have been added which have improved treatment?
  3. What percentage have a sustained virological response?
  4. How long does treatment last?
  5. How can response be monitored?
  6. Is there a HCV vaccine?

  1. Ribavirin and Pegylated interferon

  2.  Protease inhibitors and Polymerase inhibitors

  3. 90%

  4. 3 months (used to be 6 or 12 months)

  5. Molecular assays

  6. NO



  1. What type of virus is it?
  2. What are the two types?
  3. What cells does it infect?
    1. How does it cause immunosuppression?
  4. How did HIV originate?

  1. Retrovirus
  2.  HIV-1 and HIV-2 with lots of subtypes (HIV-1 subtype B is dominant)
  3. Infects immune cells

    –CD4 Lymphocytes (TH cells)


    1. due to reduction in T cell function

  4. as a zoonotic event in Africa (1930s)


  1. What is the Pathogenesis of HIV?
  2. How long does it take?
  3. What is the measure of disease progression?

  1. CD4 molecule acts as a receptor
    • Th cells, monocytes, dendritic cells and microglia.
    • Gradual immune destruction
    • Opportunistic infections- Lots of different agents – virus, bacteria, fungi, parisites
  2. Typically takes many years
  3. CD4 count is the measure of disease progression



What will Primary HIV illness present as?

fever, malaise and lymphadenopathy

Maculopapular rash may also occur

*Important to think of in glandular fever like presentation


What sorts of infections are prevalent with AIDS?

  • Viruses
    • CMV (retina, brain, gastrointestinal tract)
    • HSV (lungs, gastrointestinal tract, CNS, skin)
    • JC virus (brain - PML)
    • EBV (hairy leukoplakia, primary cerebral lymphoma)
  • Bacteria
    • Mycobacteria (e.g. Mycoplasma avium, M. tuberculosis)
    • Salmonella (recurrent, disseminated) septicemia
  • Protozoa
    • Toxoplasma gondii (disseminated, including CNS
  • Fungi
    • Cryptococcus neoformans (CNS)
    • Histoplasmosis (disseminated, extrapulmonary)
  • Tumors
    • Kaposi's sarcoma B cell lymphoma
  • Other
    • Wasting disease (cause unknown) HIV encephalopathy
  • Oral cadidiasis isnt pathopeumonic with HIV, but excessive can be good sign of immunosuppression. 



HIV Epidemiology 

  1. How many people are infected worldwide?
  2. Where is it prevalent?

  1. Over 40 million
  2. rural communities in parts of central and east Africa, up to 40% positivity

    – mostly young adults.

    –'slim' disease

    –TB is the big killer in this context


HIV Transmission

  1. What is the key transmission route for HIV?
  2. Which group is most vulnerable to HIV infection and AIDS?
  3. What transmission is more common in resource-rich countries?
  4. What transmission or more common in developing countries?


  1. Sex associated transmission

  2. homosexual men, especially the passive partner in anal intercourse.
  3. Infection is transmitted primarily from male to male and from male to female although not very efficiently compared with other STDs.
  4. Transmission from female to male (Africa and Asia)



  1. How is HIV diagnosed?
  2. What other sorts of testing is carried out?

  1. Screening assay (antigen and antibody)

    –“Duo” OR 4TH Generation

  2. •Confirmatory assays (to check specificity)

    •Second sample as check on identity

    •Avidity testing (how recent was infection). Avidity is the 'stickiness' of the antibody

    –Low avidity = infection in past 5 months (Very useful - can TARGET CONTACT TRACING TO A NARROWER TIME).



Give examples of some other useful lab tests (aside from the diagnostic tests)

  • HIV viral load
    • Response to treatment
    • Seroconversion
  • CD4 count
    • Stage of illness
    • Decision to start antiretroviral agents
  • Mutational analysis (Sequence based)
    • Resistance to anti-retroviral agents


How is HIV treated?

Name some antiretroviral therapies

  • nucleoside reverse transcriptase inhibitors (NRTIs),
  • non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • protease inhibitors (PIs)
  • Others
    • “highly active antiretroviral therapy (HAART)” combination therapy.
    • side-effects of the drugs,
      • including mitochondrial toxicity and altered fat distribution known as lipodystrophy.
    • Treatment compliance is major factor
    • Monitoring
      • plasma HIV load measurements
      • CD4 counts


Successful therapy- the incidence of AIDS and AIDS-related death in the UK has fallen by more than 40% since 1996 (despite big rises in numbers infected) 


HIV in Pregnancy

  1. What is the risk of mother to baby transmission?
  2. How can this be decreased (to <1%)
  3. How can the population be protected?

  1. 20% risk of mother to baby transmission
  2. But <1% if :
    1. Elective caesarian - unless viral load undetectable
    2. Antretroviral drugs given prophylactically
    3. Breast feeding avoided
  3. All pregnant women in UK are screened for HIV infection



•Johnny is a 30 years old, current IV drug user who shares needles. He presents with several months weight loss and recent lower respiratory tract infection and has pronounced oral candidiasis.

  1. What microbiological investigations should we do?


Weight loss, and oral canadidiasis.

Could this be an AIDS type presentation?

Want to do an HIV test - the duo assay (4th gen assay)