- 40 million cases worldwide
- Incidence – 5m/year
- Deaths – 3m/year
- Prevalence of AIDS – >3million
- Most of these cases are in women and children in Africa
- Types of virus
- HIV-1 – the most prevalent type in Europe
- HIV-2 causes a similar disease, but has a longer latency period. Uncommon outside of Africa.
- UK incidence – 6000/year in 2013, down from 7500 per year in 2005.
- 75% of cases are in men who have sex with men (MSM)
- More common in heterosexual individuals than homosexual individuals since 1999.
- 75% sexual intercourse
- 5-7% oral sex
- Evidence suggests that circumcision reduces the risk of infection by 60% – however there is some public belief that it provides immunity – it does not!
- Risks (per sexual encounter):
- Anal sex – receiving partner – between 0.1 – 3%
- Anal sex – active partner – <0.1%
- Vaginal sex – female – 1 in 100,000
- Vaginal sex – male – 1 in 200,000
- Oral sex – less than 1 in 200,000
- Blood products
- IV drug use
- Needlestick Injury
- Vertical transmission
- Child birth – 15% chance of transmission
- Child birth + breast feeding – 25%
HIV is a single stranded RNA retrovirus. The virus is incorporated into a host cell, whereby, the viral enzyme transcriptase will begin transcription of the RNA to DNA. Then, the viral enzyme integrase will integrate the DNA into the host’s.
- The host cell will then produce viral polypeptides, which are cleaved into functional viral parts by the viral enzyme protease.
- Finally, complete virions are released by the host cell via budding
Infection of cells – These new virions can now infect new cells. They are capable of entering any cell that expresses the CD4 receptor. The virus will bind to CD4 receptors with the gp120 glycoprotein. Susceptible cells include:
- CD4+ T cells
CD4+ T cells will migrate to lymphoid tissue, and release millions of virons, ready to infect new cells.
As the infection progresses, destruction of CD4+ cells leads to reduced efficacy of the host immune system.
Seroconversion – typically occurs 2-6 weeks after exposure. Is often asymptomatic, but in about 50% of cases there may be a period of fever, malaise, myalgia, pharygnitis and maculopapular rash.
- This infection often resembles glandular fever (infectious mononucleosis)
- Consider HIV in any patient with fever, malaise an widespread lymphadenopathy
Asymptomatic infection – typically, after the initial phase, patients enter a long asymptomatic period. This can last for years – typically around 5 years or more.
- 30% of patients will have a persistent generalized lymphadenopathy (PGL) – where there are lymph nodes 1cm in diameter at >2 extra-inguinal sites. This may last >3 months.
AIDS related complex (ARC) – aka – symptomatic infectionthis is a set of prodromal symptoms that precedes the onset of AIDS. It can include:
- There is marked immunodeficiency
- In the US – defined as a CD4 count <200 x 106 / L. In Australia and the UK typically defined more a clinical syndrome. The list of “AIDS defining infections” is long, but in the presence of known HIV, the occurrence of these infections can be said to confirm AIDS. The list includes things such as:
- Candidiasis of respiratory tract or oesophagus
- Chronic HSV
- Disseminated TB
- Toxoplasmosis of the brain
- Recurrent Salmonella
- Pneomocystis jiroveci pneumonia
- Lymphoma of the brain
- Invasive cervical cancer
- It takes on average about 10 years to develop, but can be seen as early as 2 years or as late as 20 years later
HIV antibody testing is typically a 2-step process. The antigen-antibody (ELISA) test is used a screening test, and if positive, diagnosis is confirmed by a secondary test (e.g. Western Blot test).
- Antigen-antibody (ELISA) test becomes positive 2-6 weeks after infection
- Current guidelines recommend a repeat test after 3 months if the initial test is negative to confirm the negative result
- The Western blot test is used to confirm the diagnosis. It detects HIV antibodies.
- Combined positive ELISA and Western blot is 99.9% accurate
Other tests associated with HIV:
- P24 antigen – present in the blood in the first 3 months of infection. Usually levels drop by the time IgG and IgM are produced (3 months). Levels rise again as immunodeficiency develops. Due to its variability it is not often useful in diagnosis
- CD4 T lymphocyte count – Used to measure immune function. A normal result is >500. A result of <200 is used by some centres as a definition of AIDS.
- HIV RNA (viral load) – can also be detected using PCR techniques during the early stages of the infection
- Used to monitor progress and effectiveness of treatment (See below)
- IgG and IgM – levels detectable after 3 months. Fall as immunodeficiency develops (try looking for P24).
- HIV point of care testing – OraQuick(R) – is a method of detecting HIV antibodies in saliva. Fast and easy – results in 10-20 minutes, but high false positive rate
HIV and TB – often co-exist, and can be a real problem.
- 30-50% of those with AIDS also have TB
- Mantoux test can be negative even in positive patients
- TB presentation is often atypical
- AFB (Acid-fast bacilli) Smear – may be negative, or have very few cells. Important to culture for sensitivities.
- All HIV positive patients should be regularly monitored for TB. Some recommend the use of isoniazid as prophylaxis in HIV positive patients.
- Hepatitis B
- Hepatitis C
- HIV type and resistance assay
- Consider testing for:
- Full STI screen
HIV RNA levels (viral load)– strongly predicts the progression to AIDS, regardless of the CD4 count!
- Patients can be ‘staged’ according to HIV RNA levels, e.g.:
- Those in the lowest quartile have an 8% chance of progressing to AIDS in 5 years, compared to 62% of those in the highest quartile.
- In the developing world, this test may be too expsenive. A total lymphocytes count may be adequate
- Total lymphocytes = 1400, then CD4 roughly =200
- This is accurate enough for predicting HIV progression
Sensitive and sympathetic discussion is typically appropriate in the first consultation(s) after diagnosis. In asymptomatic patients in particular, try to avoid technical discussions about treatment regimens.
- Provide printed fact sheets
- Discuss issues around HIV transmission and contact tracing
- Consider referral to psychology
ART – antiretroviral therapy (formerly known as HAART – highly active anti-retroviral therapy) is the mainstay of medical treatment.
- In the developed world, this is the mainstay of treatment. There is not one specific recommended regimen – essentially all regimens are experimental combinations of anti-retroviral drugs
- ART aims to reduce the rate of viral replication below detectable levels. This does not mean that replication is not occurring!
- ART should be part of a holistic care approach.
- It is a combination of two Nuceloside analogue reverse transcriptase inhibitors (NRTI’s), PLUS
- Either; a Protease Inhibitor (PI),
- Or; a non-nucleoside reverse transcriptase inhibitor (NNRTI)
Principles of therapy
Typically 3+ drugs are used in combination
Start treatment as early as possible – i.e. before CD4 count <200, ideally as soon as diagnosis is confirmed.
- Advise the patient that regimens are complex, and require strict adherence
- Monitor Viral load and CD4 count regularly.
- Ideally, viral load will be undetectable after 4 months of HAART
- If viral load is apparently erratic, consider poor adherence
- If viral load remains high despite treatment, change the regimen
Exact treatment regimens vary locally. Involve a specialist (sexual health physician) as soon as the diagnosis is made. Below is an overview of some of the classes of medications used.
NRTI’s – e.g. Zidovudine, Didanosine, Lamivudine, Emtricitabine, Tenofovir, Abacavir
- Side effect are not particularly pleasant, and include:
- Anaemia, leucopaenia, GI disturbance, rashes, myalgia, neuropathies, pancreatitis.
- CI’s: LFT disturbance, Hepatomegaly, lactic acidosis, breast feeding, anaemia. Monitor for liver problems and amylase.
Protease Inhibitors – e.g. Indinavir, Ritonavir, Saquinavir, Lopinavir
- Slow the viral spread, prolong the asymptomatic stage of the disease
- Metabolized y cytochrome P450 system – so can cause drug interactions
- Can cause metabolic syndrome (insulin resistance, hyperglycaemia, dyslipidaemia)
- Side effects: Taste disturbance, rash, pruritus (itch), hyperpigmentation, alopecia, parasthesia, myalgia, headache, dizziness, pancreatitis, anaemia, abnormal LFTs.
NNRTI’s e.g. Nevirapine, Efavirenz
- Again, involved with cytochrome P450
- Resistance occurs quickly
- Side effects
- Hepatitis, dizziness, avoid in pregnancy.
- Risk of HIV infection is <0.5%
- Tests for HIV antibodies should be done at 3,6 and 8 months to check for seroconversion
- Risk of Hep B infection is about 30%
- Make it bleed!
- But do not suck, or put in bleech
- Get the details of the ‘donor’
- Report to occupational health ASAP
- Store blood samples from both parties (onset required for the ‘donor’ blood)
- Check risk
- Related to the donor CD4 level and viral load
- Consider prophylaxis
- Low risk – may not be needed
- High risk – zidovudine – 250mg / 12h + lamivudine 150mg / 12h + indinavir 800mg / 8hr, all PO
- Do a pregnancy test before starting on prophylaxis!
- There have been about 100 cases worldwide, and 5 in the UK, of a healthcare working contracting HIV from a patient – it is rare
15% risk of vertical transmission (higher in Africa)
Methods of prevention of vertical transmission:
All HIV positive mothers should
- Take anti-retrovirals – nevirapine is recommended. If on another agent before pregnancy, switch to this once pregnant
- Consider Caesarian
- Usually elective caesarean at 38 weeks
- Vaginal delivery is a RF – if twins, the first twin is at greater risk of vertical transmission
- Abstain from breast feeding
- If all the above measures are adhered to, risk of transmission is about 2%.
- Have tests for genital infection at booking and at 28 weeks
Counseling for HIV testing
It is very important to remember that before you perform an HIV test you need to tell the patient about the implications of a positive result. You should:
Determine the level of risk (e.g. unprotected sex, number of partners, sex overseas)
Discuss the benefits of knowing if test is positive:
- Protect partner
- Reduce risk of vertical transmission
- Get treatment
Ask about major concerns e.g.:
- Telling partner / friends
- Mortgage (if can’t work)
- You don’t have an obligation to inform the partner as this would break confidentiality. Encourage patient to discuss these issues with partner – offer them to invite partner along to surgery if this would help.
- However – if the patient refuses to tell their partner, you should consult GUM specialists / MDU / MPS to discuss the cases. In some instances it may be acceptable to break confidentiality to inform those at risk.
- Again discuss effects on family, job, telling partner / friends
- Emphasize methods to reduce exposure.
- Long-term counseling – may involve making plans for death, e.g.
- Making a will
- Care of children
- Involvement of GP, palliative care services, and HIV experts
- STI Management Guidelines (Australia) – HIV
- Patient.info – Human Immunodeficiency Virus
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.