Friday, May 8, 2009

Diagnosis of HIV infection

Diagnosis of HIV infection


HIV can't be diagnosed through a medical examination or via disease symptoms. Diagnosis is only possible on the detection of the HIV virus or antibodies in body fluids (e.g. blood). Normally the presence of antibodies is tested.

The diagnostic window:
It takes some weeks before sufficient quantities of antibodies exist in the blood for the test. This period from infection to proof of infection is called the diagnostic window. The period varies from person to person and is dependent on several factors (transmission path, quantity of transferred viruses, immune system etc.).

The diagnostic window can be reduced by an average of 3 weeks with the use of an antigen (virus) test or a combination of antigen and antibody tests. For most people the time taken between infection and diagnosis is 3 months but it may take 6 months before it is possible.

diagnostic window

HIV infection and anti-body reaction
The green curve shows the concentration of the antibodies against the HIVs in the blood. The red line shows the virus concentration (antigen) in the HIV infected blood. HIV can diagnosed at the earliest after two weeks and the antibodies at the earliest 3 weeks later.

Wednesday, May 6, 2009

What's the difference between anonymous & confidential testing?

What's the difference between anonymous & confidential testing?

With anonymous testing, you don't have to give your name to anyone. With confidential testing, you supply your name during the testing process, but the healthcare system and government health agencies are required by law to keep your testing information confidential – they can't let it become public information.

In the United States, your medical records are confidential. They're protected by the Privacy Act, which was passed into law in 1974. Generally speaking, only your doctor or the facility where you have your test done have access to your medical records. However, laws vary from state to state with regard to their being required to report when someone tests positive. For instance, if you live in a state where reporting of communicable diseases is required, your doctor must report your positive test result – which will likely include your name – to the state and federal governments.

Anyone who is concerned about anonymity or disclosure should contact their local health department or any AIDS service organization hotline to find out what the law is in their area and where anonymous testing is available.

A home test, or going to an anonymous testing site – which are available through departments of health in all the states – are good ways of getting tested anonymously, which means that your name does not need to be used in order to have the test. You will have a conversation with a counselor, but your identity will still be protected.

Tuesday, May 5, 2009

Aren't there two different kinds of HIV?

Aren't there two different kinds of HIV? How do I know what I should be tested for?

The two known types of HIV are HIV-1 and HIV-2. In the United States and Europe, the overwhelming majority of HIV cases involve HIV-1. HIV-2 infections are predominantly found in West African nations. The first case of HIV-2 was discovered in the United States in 1987. Since then only 79 people with HIV-2 infections have been identified in the United States. While the CDC does not recommend routine screening for HIV-2, when someone tests for HIV-1 using ELISA/Western blot tests, there is a 60% to 90% chance that HIV-2 will be detected if it is present.

Not every test will automatically include testing for HIV-2. Anyone who thinks there's a possibility they have been exposed to HIV-2 and/or any of HIV's more rare subtypes should mention this when being tested. Among those for whom HIV-2 testing is indicated are those with sex partners from a country where HIV-2 is prevalent or people with an illness that indicate underlying HIV infection, such as an opportunistic infection, but whose HIV-1 test result was negative

Sunday, May 3, 2009

The HIV Life Cycle en español

The HIV Life Cycle
en español


Introduction

In order for viruses to reproduce, they must infect a cell. Viruses are not technically alive: they are sort of like a brain with no body. In order to make new viruses, they must hi-jack a cell, and use it to make new viruses. Just as your body is constantly making new skin cells, or new blood cells, each cell often makes new proteins in order to stay alive and to reproduce itself. Viruses hide their own DNA in the DNA of the cell, and then, when the cell tries to make new proteins, it accidentally makes new viruses as well. HIV mostly infects cells in the immune system.

Infection: Several different kinds of cells have proteins on their surface that are called CD4 receptors. HIV searches for cells that have CD4 surface receptors, because this particular protein enables the virus to bind to the cell. Although HIV infects a variety of cells, its main target is the T4-lymphocyte (also called the "T-helper cell"), a kind of white blood cell that has lots of CD4 receptors. The T4-cell is responsible for warning your immune system that there are invaders in the system.

Replication: Once HIV binds to a cell, it hides HIV DNA inside the cell's DNA: this turns the cell into a sort of HIV factory.
HIV - AIDS virus
representation of HIV