Winnie Porcelli writes in her letter to the editor ("Condoming Marriage," Tucson Weekly, Nov. 20) that columnist Tom Danehy, despite being in a monogamous heterosexual relationship since 1978, should wear a condom to avoid transmission of HIV. She states that his belief that his marriage is a "safe haven of monogamy" is "only that: a belief."
Putting aside Porcelli's presumptious claim to know how well-justified Danehy's belief in his wife's faithfulness is, is it reasonable to require anyone in Danehy's position to wear a condom? The answer is clearly no. Robert Bazell, writing in the December 2, 1991 issue of the New Republic, points out that a recent study of heterosexual couples in which one partner was infected with HIV showed that after years of unprotected intercourse only 20 percent of the uninfected women and one percent of the uninfected men became infected.
An article in the April 22, 1988 issue of the Journal of the American Medical Association estimated that use of a condom decreases one's risk of AIDS by one order of magnitude. The article estimated the probability of contracting HIV from a partner not in a high-risk group who has never been tested for HIV to be one in five million in a single sexual encounter without a condom, or one in 50 million with a condom. The probability of contracting HIV from a person who is not in a high-risk group and who has tested negative for HIV was estimated at one in five billion for a single sexual encounter with a condom or one in 500 million without a condom. At such low levels of risk, the benefits of condom use are insignificant. By contrast, the estimated probability of HIV transmission in a single sexual encounter with a person who has tested positive is one in 500 without a condom, one in 5,000 with a condom.
The level of risk can be estimated yet further by examining the breakdown of AIDS cases to date. As of September 1991, the Centers for Disease Control statistics show a total of 4,321 heterosexual males with AIDS (two percent of the total), of whom 1,701 had sex with IV drug users. Only 710 of the total had engaged in sex with a person of unspecified risk, a category into which Danehy's wife surely falls. Among women, there are 6,668 cases of AIDS from heterosexual transmission (three percent of the total), 4,117 of whom have had sex with IV drug users and 625 of whom have had sex with bisexual males. Nine hundred thirty-nine women with AIDS contracted the virus from sex with a person of unspecified risk. These are not annual figures, these are the total figures.
[Note added 2005-05-30: A paper on HIV transmission to Thai soldiers from prostitutes found the risk to be between 1 in 18 to 1 in 30 per act of heterosexual intercourse. Mastro, TD; Satten, GA; Nopkesorn, T; Sangkharomya, S; Longini, IM Jr., "Probability of female-to-male transmission of HIV-1 in Thailand," Lancet 1994 Jan. 22; 343(8891):204-7; this doesn't invalidate the information above, but suggests that if there are other STDs present, it is much easier to transmit HIV heterosexually. This reference came from a Steven Harris discussion here.]