Important note: Information in this article was accurate in 2005. The state of the art may have changed since the publication date. I found out today that my gay cousin, may be infected with AIDS. His boyfriend has had it for 5 years and never told him anything, he found out because he found the medicine and looked it up online and finally the guy admitted it. They've been having unprotected sex for about 7 months, my cousin had the HIV test and it came back as negative. What are the chances of the test really being negative.
Rodger MacArthur, M.D.
Wayne State University
Division of Infectious Diseases
There are many issues brought up by this question. The situation described is increasingly common in North America. Specifically, many HIV-infected persons have unprotected intercourse without informing their partners of their HIV status, despite state laws mandating disclosure. It is not against state law for HIV- infected persons to have sexual intercourse (protected or unprotected), but most states mandate that HIV-infected persons inform any sexual or needle-sharing partner of their HIV-positive status prior to engaging in either of these risk activities. While many HIV-infected persons may be unaware of the relevant state laws or even their own HIV-infected status, many others knowingly violate (or ignore) the laws for the following reasons: 1) fear that they will be rejected or not be allowed to have intercourse if they inform their partners of their status beforehand; 2) fear that they will be rejected because of lack of disclosure (deceit) if they inform their partners afterwards.
Data from discordant couples (one partner HIV-positive, the other HIV-negative) followed for many months indicate that approximately 1/3 of the HIV-negative partners will be come HIV- positive after one year. Included in these studies are couples who always use protection during intercourse, as well as those who use protection inconsistently or not at all. In addition, the studies include couples who have sexual intercourse frequently as well as those who have sexual intercourse infrequently. The more frequently an HIV-negative individual engages in unprotected intercourse with an HIV-infected person, the greater is the chance of becoming infected.
There are additional factors that affect the risk of becoming HIV-infected through unprotected intercourse. Anal or vaginal receptive intercourse is riskier than anal or vaginal insertive intercourse because virus-containing fluid (semen) is in contact with mucosal membranes in the receptive partner for longer periods of time than for the insertive partner. Trauma (bleeding) increases the risk for both partners, as does the presence of concurrent sexually-transmitted diseases (such as syphilis and gonorrhea) or open sores on or near the genitalia.
The amount of virus in the blood of the infected person (viral load) also is related to risk of transmission. Thus, an HIV- infected person is most "contagious" when initially infected and late in the course of infection, when viral loads are highest. Conversely, risk of transmission is lowest in persons who have had "undetectable" viral loads as a result of 100% pill-taking adherence to effective medications for prolonged periods of time. Such individuals are at much lower (but not zero) risk of transmitting the virus to others. On the other hand, an HIV- infected person on antiretroviral medication with detectable amounts of virus in the blood is at increased risk of transmitting resistant virus to others if infection does occur.
HIV antibody testing is a reliable method for determining current infection status. While there are falsely-positive results (typically in low-risk populations), a negative test is only likely to be incorrect (falsely-negative) in the 4-12 week period of time immediately following infection (sometimes referred to as the "window" period). The questioner's cousin should be advised to have another HIV antibody test performed 3-6 months after the initial test. If that second test is also negative, then it can be assumed with more than 99.99% certainty that her cousin is truly HIV-negative, assuming no additional risk behavior occurred in the meantime. Finally, it would be prudent for her cousin to use latex condoms during sexual activity, as condoms, when properly worn, reduce the risk of infection with HIV and other sexually-transmitted diseases to approximately zero.
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