Introduction

HIV (Human Immunodeficiency Virus) is - as the name suggests - a virus; more specifically, it is a lentivirus (lentiviruses are a particular genus of retrovirus). This particular lentivirus infects cells of the immune system, which - unfortunately - eventually leads to their destruction, by various means. Over time, with the loss of progressively more cells, the immune system becomes severely debilitated. One important type of cell which is targeted by HIV is the CD4⁺ T cell. When the number of these cells falls below 200 cells per µL of blood, a patient is said to have developed AIDS (Acquired ImmunoDeficiency Syndrome). An alternative criterion for a diagnosis of AIDS is the presence of certain diseases, born of a compromised immune system. With the onset of AIDS, a patient is at an increased risk of opportunistic infection and of developing cancer and, without treatment, their immune system will be unable to respond effectively. Ultimately, this will lead to the premature death of the patient.

HIV is transmitted from person to person through bodily fluids, viz. semen,  pre-ejaculate, vaginal fluid, blood, or breast milk. Approximately 95% of cases diagnosed in the UK in 2010 were the result of sexual activity. Transmission can also occur, inter alia, through the use of a contaminated needle; during childbirth, or when breastfeeding; or through transfusion of the blood of somebody who is HIV positive.

Transmission of HIV can be effectively prevented by practising safe sex, especially through the correct and consistent use of condoms. Pregnant women can also ensure the safety of their child by being tested for HIV during pregnancy. With appropriate medical treatment and, where indicated, birth by Caesarean section, the chances of an HIV positive mother passing the virus onto her baby fall from ≈ 25% to ≈ 2%. Obviously, pregnant women who know they are HIV positive should seek medical advice. Care should also be taken by healthcare professionals and by anybody who uses - or otherwise comes into contact with - needles and syringes. On no account should needles be shared.

Without treatment, the prognosis - according to UNAIDS estimates - is 9-11 years from the initial infection with HIV. Upon developing full-blown AIDS, without treatment, the prognosis is poor - with 6-19 months being the estimated survival time. Adequate medical treatment, particularly the use of high active antiretroviral therapy (HAART), can significantly improve this prognosis. With early detection, a patient can be expected to live for a further 20-50 years; although the prognosis deteriorates the later the treatment is begun.

Because of this, it is very important that HIV/AIDS be well-understood and that HIV positive people be able to get tested and be able to receive the appropriate medical treatment. Sadly, a great deal of ignorance and social stigma continues to surround HIV/AIDS. Many HIV positive people suffer discrimination, fear and violence because of the disease. HIV/AIDS is also surrounded by sham cures, superstition and denialism. The presidency of Thabo Mbeki in South Africa is estimated to have contributed to 330,000-340,000 deaths as a result of AIDS, due to the denialism of that regime. The policy of the Catholic church with respect to condom use is also widely-known: this policy has discouraged (if not prevented) correct condom use, which remains the best protection against the spread of HIV.

I, therefore, intend to present here as thorough an explanation as possible of what HIV is, what it does and how it does it. In order to understand HIV, we must begin by understanding the immune system, which is what HIV affects. Having covered the immune system, we can proceed to examine the virus itself and how it replicates. This will require a thorough knowledge of the cell and of genetics. This will allow us to fully understand HIV and how infection may be treated. This sketch I present here may change somewhat as I go along and I might actually have to have recourse to a certain amount of moving and fiddling and "rejigging." I will of course try, though, to only hit the "Publish" button when I think I've got a finished product worth putting up.