HIV refers to the human immunodeficiency virus. Being infected with HIV is referred to as being HIV positiveAIDS refers to acquired immunodeficiency syndrome. AIDS occurs as an HIV infection progresses, and the person becomes immunodeficient. This immunodeficiency leads to opportunistic infections and several AIDS-defining illnesses, such as Kaposi’s sarcoma. AIDS is now mostly referred to as late-stage HIV.



HIV is an RNA retrovirusHIV-1 is the most common type, and HIV-2 is rare outside West Africa. The virus enters and destroys the CD4 T-helper cells of the immune system.

An initial seroconversion flu-like illness occurs within a few weeks of infection. The infection is then asymptomatic until the condition progresses to immunodeficiency. Immunodeficient patients develop AIDS-defining illnesses and opportunistic infections. This progression occurs potentially years after the initial infection.



HIV is not transmitted through day-to-day activities, including kissing. It is spread through:

  • Unprotected anal, vaginal or oral sexual activity
  • Mother to child at any stage of pregnancy, birth or breastfeeding (called vertical transmission)
  • Mucous membrane, blood or open wound exposure to infected blood or bodily fluids, for example, through sharing needles, needle-stick injuries or blood splashed in an eye


AIDS-Defining Illnesses

There is a long list of AIDS-defining illnesses associated with end-stage HIV infection. These occur where the CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear.

Examples of AIDS-defining illnesses include:

  • Kaposi’s sarcoma
  • Pneumocystis jirovecii pneumonia (PCP)
  • Cytomegalovirus infection
  • Candidiasis (oesophageal or bronchial)
  • Lymphomas
  • Tuberculosis



Many people with HIV do not know they are infected, and these patients are at risk of complications and spreading the disease. Generally, the earlier a patient is diagnosed, the better the outcome. HIV is a treatable condition, and most patients are fit and healthy on treatment.

We should test practically everyone admitted to hospital with an infectious disease for HIV, regardless of their risk factors. Patients with any risk factors should be tested.

It can take up to three months to develop antibodies to the virus after infection. Therefore, HIV antibody tests can be negative for three months following exposure, and repeat testing is necessary if an initial test is negative within three months of exposure to the virus.

Patients need to give consent for a test. Verbal consent should be documented before a test. Consent only needs to be as simple as “are you happy for us to test you for HIV?” Patients no longer require formal counselling or education before a test.



Antibody testing is the typical screening test for HIV. This is a simple blood test. Patients can request an antibody testing kit online for self sampling at home, which they post to the lab for testing.

Testing for the p24 antigen, checking directly for this specific HIV antigen in the blood. This can give a positive result earlier in the infection compared with the antibody test.

PCR testing for the HIV RNA levels tests directly for the number of viral copies in the blood, giving a viral load.



CD4 Count

The CD4 count is the number of CD4 cells in the blood. These are the cells destroyed by the virus. The lower the count, the higher the risk of opportunistic infection:

  • 500-1200 cells/mm3 is the normal range
  • Under 200 cells/mm3 is considered end-stage HIV (AIDS) and puts the patient at high risk of opportunistic infections

Viral Load (VL)

Viral load is the number of copies of HIV RNA per ml of blood. “Undetectable” refers to a viral load below the lab’s recordable range (usually 50 – 100 copies/ml). The viral load can be in the hundreds of thousands in untreated HIV.



Specialist HIVinfectious disease or GUM centres manage patients with HIV. Treatment involves a combination of antiretroviral therapy (ART) medications. ART is offered to everyone with a diagnosis of HIV irrespective of viral load or CD4 count. Some regimes involve only a single combination tablet, taken once daily, with the potential to suppress the infection completely. Specialist blood tests can establish the resistance of each HIV strain to different medications and help tailor treatment. The BHIVA guidelines (2015) recommend a starting regime of two NRTIs (e.g. tenofovir and emtricitabine) plus a third agent.

Treatment aims to achieve a normal CD4 count and undetectable viral load. As a general rule, when a patient has a normal CD4 and an undetectable viral load on ART, treat their physical health problems (e.g. routine chest infections) as you would an HIV negative patient. When prescribing for patients on ART, be aware and carefully check for any medication interactions with the HIV therapy.


Highly Active Anti-Retrovirus Therapy (HAART) Medication

There are a number of classes of HAART medications that work slightly differently on the virus:

  • Protease inhibitors (PIs)
  • Integrase inhibitors (IIs)
  • Nucleoside reverse transcriptase inhibitors (NRTIs)
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • Entry inhibitors (EIs)


Additional Management

Prophylactic co-trimoxazole (Septrin) is given to patients with a CD4 under 200/mm3 to protect against pneumocystis jirovecii pneumonia (PCP).

HIV infection increases the risk of developing cardiovascular disease. Patients with HIV have close monitoring of cardiovascular risk factors and blood lipids. Appropriate treatment (e.g. statins) may be required to reduce their risk of developing cardiovascular disease.

Yearly cervical smears are required for women with HIV. HIV predisposes to developing human papillomavirus (HPV) infection and cervical cancer, so female patients need close monitoring to ensure early detection of these complications.

Vaccinations should be up to date, including influenza, pneumococcal, hepatitis A and B, tetanus, diphtheria and polio vaccines. Patients should avoid live vaccines.


Reproductive Health

Advise condoms for vaginal and anal sex and dams for oral sex, even when both partners are HIV positive. If the viral load is undetectable, transmission through unprotected sex is unheard of, even in extensive studies, although infection is not impossible. Partners should have regular HIV tests.

Where the affected partner has an undetectable viral load, unprotected sex and pregnancy may be considered. It is also possible to conceive safely through techniques like sperm washing and IVF.


Preventing Transmission During Birth

The mother’s viral load will determine the mode of delivery:

  • Normal vaginal delivery is recommended for women with a viral load < 50 copies / ml
  • Caesarean section is considered in patients with > 50 copies copies / ml and in all women with > 400 copies / ml
  • IV zidovudine should be given during the caesarean if the viral load is unknown or there are > 10000 copies / ml

Prophylaxis treatment may be given to the baby, depending on the mothers viral load:

  • Low-risk babies, where the mother’s viral load is < 50 copies per ml, are given zidovudine for four weeks
  • High-risk babies, where the mother’s viral load is > 50 copies / ml, are given zidovudinelamivudine and nevirapine for four weeks

This description of measures to prevent vertical transmission is an over-simplified illustration of the BHIVA guidelines. You don’t need to know the details for your medical school exams, but it is helpful to be aware of the basic principles.


Breast Feeding

HIV can be transmitted during breastfeeding, even if the mother’s viral load is undetectable. Breastfeeding is not recommended for mothers with HIV. However, if the mother is adamant and the viral load is undetectable, sometimes it is attempted with close monitoring by the HIV team.


Post-Exposure Prophylaxis

Post-exposure prophylaxis (PEP) can be used after exposure to HIV to reduce the risk of transmission. PEP is not 100% effective and must be commenced within a short window of opportunity (less than 72 hours). The sooner it is started, the better. A risk assessment of the probability of developing HIV should be balanced against the side effects of PEP.

PEP involves a combination of ART therapy. The current regime is Truvada (emtricitabine and tenofovir) and raltegravir for 28 days.

HIV tests are done immediately and also a minimum of three months after exposure to confirm a negative status. Individuals should abstain from unprotected sexual activity for a minimum of three months until confirmed as negative.


Last updated July 2020