Wednesday, 29 August 2012

Human immunodeficiency virus (HIV)

Human immunodeficiency virus (HIV) is a lentivirus – a type of retrovirus – and is the cause of acquired immunodeficiency syndrome (AIDS). AIDS is a condition in humans that leads to progressive failure of the immune system, which allows infections and cancers to thrive.

HIV is one of the most widely known sexually transmitted infections in the world, and is classed as a pandemic infection by the World Health Organisation. Approximately 35 million people have HIV globally, of which 17 million are women and 3.5 million are under the age of 15. Sub-Saharan Africa is considered the area most effected by HIV/AIDS; around 6 million people are infected with HIV/AIDS, and an estimated 66% of all deaths linked to HIV/AIDS globally occurred in this region in 2009, compared with under 200,000 deaths in the US, under 600 in the UK, and 53 in Canada. Despite being a pandemic infection, the spread and morality rates associated with HIV/AIDS have declined in recent years, partly due to improvement in medication and also due to raising global awareness amongst the population. In 2010 there were 1.8 million deaths linked to AIDS, down from 3.1 million in 2001. It is estimated that around 20% of those infected with HIV/AIDS are unaware of the condition. In total HIV/AIDS has led to over 32 million deaths since it was recognised in 1981.

Contrary to popular believe HIV is not a single virus, but a series of different strains. It is possible to be infected by more than one of these strains, which is known as HIV superinfection. HIV is transmitted through several methods, including sexual intercourse, exposure to infected body fluids, and from mother to child during pregnancy, delivery or breastfeeding. There is no risk of contracting the infection from faeces, nasal secretions, vomit, saliva, sweat, tears or urine except where these things may have been contaminated with blood. Again contrary to popular belief there are more cases of male-to-female or female-to-male infections than there are male-to-male or female-to-female infections.

Sexual transmission of HIV more often occurs between partners that have unprotected sex, although the actual percentage chance of transmitting the disease is relatively low, less than 1% for both male-to-female and female-to-male intercourse per act. The risk of transmission through anal intercourse is higher than for any other type of intercourse a 1.4% per act. Other sexually transmitted infections, such as genital ulcers, gonorrhoea and herpes, significantly increase the chance of spreading the infection, up to fivefold in the case of gonorrhoea. The risk of spreading the disease diminishes over time, with the first 2 and a half months of infection carrying the greatest chance of passing on the virus. In some countries certain professions, such as porn actors and actresses as well as prostitutes and escorts, are required by law to have periodic STI tests, including tests for HIV/AIDS. The vast majority of those infected with AIDS do not seek early diagnosis, and only receive confirmation when the infection reaches the later stages or severe immunodeficiency has become apparent.

There is currently no known cure for HIV or AIDS, and life expectancies for those diagnosed with the infection range from 10 to 40 years, depending on whether they receive treatment or not.

Signs and Symptoms

HIV/AIDS presents with varying symptoms depending on the stage of infection. These stages are separated out into the primary infection stage, the clinical latent infection stage, the early symptomatic HIV infection stage, and finally the progression to AIDS.

The primary infection stage occurs one to two months after the virus has entered the body, and is characterised by the development of an array of flu-like illnesses. These illnesses can last up to a few weeks, and symptoms can include fever, headaches, oral or genital ulcers, swollen lymph glands, diarrhoea, joint pain, night sweats, rashes and muscle soreness. Symptoms at this stage may go unnoticed as they can be quite mild, however the actual amount of the virus in the blood stream is particularly high to allow for efficient spread through the body, more so than during the following stages.

The second stage of infection – known as the latent stage – is often marked by no characteristic symptoms at all. Some individuals may experiences constant swelling of the lymph nodes, but this is uncommon. The latent stage of infection generally lasts between 8 and 10 years, but some individuals may progress to more severe stages far sooner.

The third stage of infection – known as the early symptomatic HIV infection – is marked by a return to similar but more constant illnesses as outlined in the primary stage. These can include fever, fatigue, swollen lymph nodes, diarrhoea, weight loss, coughing and shortness of breath.

The final stage of a HIV infection is the progression to AIDS. Without treatment this typical occurs between 8 to 10 years after initial infection. At this stage the immune system has been severely damaged, and has made the infected person more susceptible to opportunistic infections that would otherwise not trouble a person with a healthy immune system. Symptoms may include night sweats, fever (higher than 38C) for several weeks, coughing and shortness of breath, chronic diarrhoea, unusual white spots or lesions in the tongue and mouth, headaches, persistent and inexplicable fatigue, blurred and distorted vision, weight loss, and skin rashes and lesions.

HIV can also present with a number of related conditions, which can include tuberculosis, salmonellosis, cytomegalovirus, candidiasis, cryptococcal meningitis, toxoplasmosis, and cryptosporidiosis. Cancer may also occur during HIV infection, the most common being Kaposi’s sarcoma and lymphomas.

Diagnosis and Treatment

Diagnosis of HIV/AIDS is done via laboratory testing and then staged based on which signs and symptoms the patient displays with. A doctor or medical professional will take samples of blood and/or saliva, which will then be checked for the presence of certain antibodies that are produced by the immune system to fight HIV infections. Another test involves checking for HIV antigen, which is a protein produced by the virus upon infection. Of the two the former takes the longest – up to 12 weeks – whilst the latter can confirm or rule out HIV within days of first being infected.

Once a base diagnosis is made, more tests may be required. These can include a CD4 count (which checks to see how many CD4 cells are in your blood stream), viral load (to test the amount of the virus in your blood), and drug resistance (to test whether the strain of HIV you have contracted is resistant to particular anti-HIV medications). All of these tests are used to tailor and appropriate level of care and management depending on the stage of infection.

There is no cure for HIV/AIDS at this time, but there are a number of medications that can help to delay the progression of the infection. Different medications block the virus in different ways, so it is quite common for as many as three different types of medication to be used at a time. The types of medication include Non-nucleoside reverse transcriptase inhibitors (NNRTIs) (which prevent the virus from making copies of itself), nucleoside reverse transcriptase inhibitors (NRTIs) (which effectively corrupt certain components that the virus needs to make copies of itself), Protease inhibitors (PIs) (which disables another protein that the virus needs to make copies of itself), Entry or fusion inhibitors (which block the virus from entering the CD4 cells), and integrase inhibitors (which again prevent the virus from integrating itself with CD4 cells).

During treatment for HIV/AIDS there is a high incidence of side effects due to the number of medication that needs to be taken, as well as any medication that is needed to control and mitigate the spread of co-infectious diseases and cancers. Side effects can include severe nausea, vomiting, diarrhoea, abnormal heartbeats, shortness of breath, skin rashes, weak bones and potential bone death in joints.

As treatment is an ongoing process tests are carried out to measure viral load and CD4 count on a regular basis so that the treatment regime may be altered to best deal with the infection.


Post a Comment