The human Immunodeficiency Viruses

HIV is caused by the Human Immunodeficiency Virus. It is transmitted via sexual contact, used needles, bodily fluids and from mother to baby. If not treated it can progress to Acquired Immunodeficiency Syndrome, also known as AIDS. There are two main strains of HIV known as HIV-1 and HIV-2. In 2009 an estimated 2.6 million people globally became infected with HIV-1.

This was a 21% decrease on 1997, during the AIDS epidemic, however in some areas of the world such as Eastern Europe and Central Asia incidence tripled from 2001-2009 for reasons related to sex work and drug use. The virus has been able to spread effectively across the world due to its ability to move between groups and individuals with widely different risk behaviours; so what is HIV and how is it prevented and treated?

During early infection, the HIV-1 virus replicates quickly. People often experience flu-like symptoms two to four weeks after infection. These symptoms include, but are not exclusive to, fever, chills, rashes, night sweats and muscle fatigue.

Studies have shown HIV may have jumped from Chimpanzees to humans as early as the 1800s. HIV-1 is the most prevalent form of HIV. One group of HIV-1 infections are Group M subtypes. These are the most common form of HIV with ‘M’ standing for ‘Major’ due to their widespread incidence across the globe. Group M is further divided into nine subtypes: A, B, C, D, E, F, G, H and I. The subtypes are classified into these nine groups due to differences in their genetic information.

While group M subtypes of HIV-1 are widespread across the globe, HIV-2 infections are mainly isolated to West Africa. It is believed HIV-2 was first transmitted to humans in the first half of the 20th Century. HIV-2 is less easily transmitted due to lower viral loads and for this reason, it has stayed isolated on the African continent.

There is no known cure for HIV however antiretroviral treatments (ART) can be used to slow down the progression of the disease and decrease transmission risk. Due to the long term use of antiretrovirals required for patients to live a long and healthy life, there has been much research into the safety and tolerability of these treatments. Most often antiretrovirals are combined for maximum efficacy in what is known as combined antiretroviral treatment (cART). cART emerged in the 1990s and has been responsible for a significant decrease in AIDS related deaths. The focus of future research is aimed at simplifying the treatment options available instead of having to use a combination of drugs.

Despite changes in treatment and prevention the rate of HIV infection has remained relatively unchanged over the past decade. Recent studies strongly indicate the value of antiretroviral treatments as prevention in couples.

Those taking cART had a 96% reduction in HIV transmission to their uninfected partners. A study conducted in 2002 showed that while consistent use of condoms during sexual intercourse significantly decreased the risk of HIV infection, it was not 100% effective. For this reason the only guaranteed way to prevent the transmission of HIV is abstinence.


Milad Rouf Final Year Medical Student, Cardiff University.

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Davis-Beaty , K.R. & Weller, S.C. 2002. Condom effectiveness in reducing heterosexual HIV transmission. Cochrane Database of Systematic Reviews. 1, pp.