How is HIV Transmitted?
en español
Introduction
Human immunodeficiency virus (HIV) was established as the cause of the acquired immunodeficiency syndrome (AIDS) in 1983. Ever since then, a lot of research has been conducted and a great deal of information has been generated regarding the ways HIV can be transmitted from one person to another.
The problem with much of the information about HIV transmission, especially on the Internet, is that it speaks in very general terms. All too often, advice from one site will directly contradict advice from another site as well. For example, some sources refer to oral sex as "risky," whereas others say it is "low risk" or "no risk." This can be very frustrating and it also leads to the spread of misinformation, and frequently a lot of unnecessary worry, about the transmission of HIV.
HIV infection—and HIV testing—is a medical issue. We have developed this lesson to provide straightforward and accurate information regarding HIV transmission. However, it is important to stress that this lesson—and other sources of HIV information on the Internet—should not be consulted as an alternative to medical care and testing. If you fear that you have been exposed to HIV—regardless of how low the perceived risk and no matter how much information you find on the Internet—you need to get in touch with your health care provider or an HIV testing center.
Tuesday, November 3, 2009
Sunday, November 1, 2009
WHAT IS VIRAL LOAD?
WHAT IS VIRAL LOAD?
The viral load test measures the amount of HIV virus in your blood. There are different techniques for doing this:
* The PCR (polymerase chain reaction) method uses an enzyme to multiply the HIV in the blood sample. Then a chemical reaction marks the virus. The markers are measured and used to calculate the amount of virus. Roche and Abbott produce this type of test.
* The bDNA (branched DNA) method combines a material that gives off light with the sample. This material connects with the HIV particles. The amount of light is measured and converted to a viral count. Bayer produces this test.
* The NASBA (nucleic acid sequence based amplification) method amplifies viral proteins to derive a count. It is manufactured by bioMerieux.
Different test methods often give different results for the same sample. Because the tests are different, you should stick with the same kind of test (PCR or bDNA) to measure your viral load over time.
Viral loads are usually reported as copies of HIV in one milliliter of blood. The tests count up to about 1 million copies, and are always being improved to be more sensitive. The first bDNA test measured down to 10,000 copies. The second generation could detect as few as 500 copies. Now there are ultra sensitive tests for research that can detect less than 5 copies.
The best viral load test result is “undetectable.” This does not mean that there is no virus in your blood; it just means that there is not enough for the test to find and count. With the first viral load tests, “undetectable” meant up to 9,999 copies! “Undetectable” depends on the sensitivity of the test used on your blood sample.
The first viral load tests all used frozen blood samples. Good results have been obtained using dried samples. This will reduce costs for freezers and shipping.
The viral load test measures the amount of HIV virus in your blood. There are different techniques for doing this:
* The PCR (polymerase chain reaction) method uses an enzyme to multiply the HIV in the blood sample. Then a chemical reaction marks the virus. The markers are measured and used to calculate the amount of virus. Roche and Abbott produce this type of test.
* The bDNA (branched DNA) method combines a material that gives off light with the sample. This material connects with the HIV particles. The amount of light is measured and converted to a viral count. Bayer produces this test.
* The NASBA (nucleic acid sequence based amplification) method amplifies viral proteins to derive a count. It is manufactured by bioMerieux.
Different test methods often give different results for the same sample. Because the tests are different, you should stick with the same kind of test (PCR or bDNA) to measure your viral load over time.
Viral loads are usually reported as copies of HIV in one milliliter of blood. The tests count up to about 1 million copies, and are always being improved to be more sensitive. The first bDNA test measured down to 10,000 copies. The second generation could detect as few as 500 copies. Now there are ultra sensitive tests for research that can detect less than 5 copies.
The best viral load test result is “undetectable.” This does not mean that there is no virus in your blood; it just means that there is not enough for the test to find and count. With the first viral load tests, “undetectable” meant up to 9,999 copies! “Undetectable” depends on the sensitivity of the test used on your blood sample.
The first viral load tests all used frozen blood samples. Good results have been obtained using dried samples. This will reduce costs for freezers and shipping.
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