3 unadressed questions
May 2, 1997
Hello Rick-Below I have asked three questions that in your internet service I have found to be unadressed. I was hoping you could answer them-Thanks 1.Will hiv survive for the same amount of time in both water and air or is their a difference? 2.I have noticed that a few body substances have not been addressed regarding their hiv carrying status. Do feces, acne fluid(puss), or nasal fluids carry hiv? 3. Just what is meant by saying that hiv tests are "more than 99.9 percent accurate?" Is the sample size for this the population of the world(around 6 billion people)so that the chances for a false negative would be about 1 in 6 billion? or what?
Response from Mr. Sowadsky
Hi. Thank you for your questions. Let me answer them one at a time.
1. Will hiv survive for the same amount of time in both water and air or is their a difference?
The answer to this question can be found in the post, "let's clear something up".
2. I have noticed that a few body substances have not been addressed regarding their hiv carrying status. Do feces, acne fluid (puss), or nasal fluids carry hiv?
Feces do not normally have HIV in them. However, if feces are visibly contaminated with blood, then there would be a risk. Feces are primarily risky for bacterial diseases (like E. coli), parasitic infections (like Cryptosporidium and Giardia), and certain viral infections (like Hepatitis A). Body fluids such as pus or nasal secretions normally do not have high concentrations of HIV, that would pose a significant risk to other people. However, since white blood cells and blood can sometimes be found in pus and nasal secretions, one should avoid contact with these body fluids. However the primary risks for these body fluids are for other infectious diseases, other than HIV. I am not aware of any cases where HIV has been transmitted by feces, nasal secretions, or pus.
3. Just what is meant by saying that hiv tests are "more than 99.9 percent accurate?" Is the sample size for this the population of the world (around 6 billion people) so that the chances for a false negative would be about 1 in 6 billion?
When tests are more than 99% accurate, it means that, through clinical trials, the test is shown to give a positive result more than 99% of the time in persons who are known to be truly positive (this is called sensitivity). In addition, if a test is more than 99% accurate, this also means that the test would give a negative result in persons who are truly negative (this is called specificity). The best tests are those that have both a high sensitivity, and a high specificity. The ELISA/Western Blot antibody tests are more than 99% accurate in both sensitivity and specificity, as long as the person waits 6 months or more after their last possible exposure to the virus. This is as accurate as any tests could ever be.
For obvious reasons, we cannot sample the entire world's population to determine the accuracy of the test. Researchers therefore use representative samples of people to determine the accuracy of tests while these tests are in clinical trials. By using representative samples of people, researchers can then adequately evaluate the accuracy of tests. Before a test can be approved, it must be shown to be accurate, and the test population must be shown to be representative. There are research methods that can be used to make sure that a representative sample of people was used during clinical trials of any new test.
If you have any further questions, please feel free to call the Centers for Disease Control at 1.800.232.4636 (Nationwide).
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