Question:

About 5 1/2 weeks ago I had unprotected sex, at 4 weeks and 2 days I had an HIV test that was negative. but for the last week or so I have been itchy- mainly on my arms, legs, a little on my back and even on my scalp. I havent really seen any bumps, maybe a few little ones on my forearm. I do have some red blotchy marks on my legs and arms but that is about it. I have had no fever, sore throat or any symptoms. Does this sound typical for the ARS rash, or do you think its something else???

Please respond- i just need a little reassurance until i have my repeat test at 3 months.

Answer provided by:

Rodger MacArthur, M.D.
Wayne State University
Division of Infectious Diseases

There are many important aspects to this question. One-time unprotected intercourse (receptive vaginal) is a known risk factor for acquiring HIV infection. If the male partner in this case is truly HIV-positive, then the chances of transmitting HIV infection to the female partner from this one episode of vaginal insertive intercourse are estimated at between 0.3% to 3%, depending on many factors. Factors which increase the risk of transmission of HIV include the male's HIV RNA level in blood and semen (viral load), with higher levels increasing the risk; 2) the presence of abrasions or open sores on vaginal mucosa or penis (perhaps from trauma related to intercourse), the effect of which is to increase the likelihood of significant partner-to-partner blood contact; and 3) the length of time that the infected fluid (semen) is in contact with the vaginal mucosa.

The risk of acquisition of HIV through receptive vaginal intercourse from a partner whose HIV status is not known also depends on the prevalence of HIV in the population to which the male partner belongs. In other words, the approximate risk of HIV-infection could be estimated by multiplying the risk from one-time vaginal intercourse with a person known to be HIV-infected (0.3% to 3%) by the chance of the person actually being HIV-infected. In the United States, 0.4% of the entire population is estimated to be HIV-infected. In comparison, the prevalence of HIV in some some countries in Africa is an astounding 40%, or 100 times the prevalence in the United States. In sexually-transmitted disease clinics throughout the United States, the HIV-positive rates are between 2% and 5%. In urban areas in the United States, such as Detroit, the HIV-positive rate of persons seeking medical care through an emergency room for any reason is about 1.5%. Thus, even assuming a 2% risk of the questioner's partner being HIV-infected, her chances of acquiring HIV through the one act of sexual intercourse are probably in the range of 1 in 5000 (2% risk of her partner being HIV-positive x 1% risk of HIV acquisition from the one-time sexual intercourse risk factor). While these odds are low, it is likely that at least 1/3 of the 40,000 annual new HIV infections in the United States are acquired through unprotected vaginal intercourse.

The correct use of latex condoms decreases the risk of acquisition of HIV to approximately zero. Condoms were not used in this case, and the questioner is now concerned about her risk of HIV acquisition. An initial HIV antibody test was negative at 4 weeks, and there were no obvious signs or symptoms to suggest the acute retroviral syndrome in this case. As the questioner points out, fever and sore throat, common features of the acute retroviral syndrome, were not present. Other findings seen in the acute retroviral syndrome include: 1) enlarged lymph nodes; 2) headache; 3) abdominal pain; and 4) rash. The rash described in this case is not typical of the rash seen in the acute retroviral syndrome, which typically is generalized, non-pruritic (non-itchy), and faintly erythematous (red; but not "blotchy"). The acute retroviral syndrome is estimated to occur in 50-70% of persons who ultimately seroconvert from HIV-negative to HIV-positive, and occurs 2-6 weeks after exposure to HIV.

It is recommended that persons exposed to HIV-infected blood or sex fluid (semen or vaginal secretions) undergo HIV antibody testing at the initial visit, at 4-6 weeks after the exposure, and again at 3 months and 6 months after the exposure. An antibody response (positive test) can be seen as early as 3-6 weeks after exposure to HIV. Over 95% of persons who ultimately seroconvert from HIV-negative to HIV-positive do so by 3 months after the exposure. By 6 months, the risk of a falsely negative HIV antibody test approximates zero. On the other hand, false positive tests do occur, and the frequency of a falsely positive test increases as the prevalence of HIV in the relevant population decreases. In other words, the lower the chances are that the questioner's partner is truly HIV-infected, the greater is the chance that the questioner's HIV test will come back falsely positive. If an individual is from a truly low-risk population, then the chance of a false positive HIV antibody test may be as high as 5% -10% (of all "positive" test results). Consequently, it generally is not recommended for persons to get HIV antibody testing done after every episode of unprotected intercourse. The preferred option is to use latex condoms during sexual intercourse.

In summary, it is extremely unlikely that the questioner's "itchy bumps" are a manifestation of the acute retroviral syndrome. It also is unlikely that she will have acquired HIV infection from the described one episode of unprotected sexual intercourse with a partner whose HIV antibody status is unknown and who does not have any reported risk factors for HIV infection.

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