There are about 750,000 San Franciscans. A reduction in annual seroconversions of 100 per 100,000 thus means that 750 citizens will avoid HIV infection each year, if the prevention work meets the objective. The 1997-98 cost per infection thereby avoided is about $8,200,000/750 = $11,000. This is a fine bargain, in view of the smallness of $11,000 in comparison to the per-person costs of HIV disease treatment, or to the (immeasurable) value of the years of life that might be lost to AIDS.

The AIDS Office's RFP is typical of the kind of well-organized, generously funded HIV prevention strategy seen in the best-served parts of the First World. What about the Third World? What about the world's newborns at risk for HIV, 99.5% of whom are born in the Third World?

The Global AIDS Coalition estimates that 400,000 new mother-to-child HIV infections (generally "perinatal transmission") occur each year. Most of these infections are preventible. For example, here's an outline of a simple two-step, worldwide campaign against perinatal HIV transmission:

All pregnant women are offered free HIV screening

Those women who test HIV+ are offered free AZT dosing during the later stages of their pregnancy, aimed at reducing HIV transmission to their infants

The cost of AZT treatment for a minimal protocol (100 mg., 5 times a day, from the 24th through the 40th week of pregnancy) is about $1,000 per pregnant woman, at the prevailing U.S. prices for AZT. The per-woman cost of HIV screening is negligibly small, and of course has multiple potential benefits other than perinatal transmission prevention.

The average of a number of studies suggests that 25% of HIV+ pregnant women will transmit HIV to their infants, and that two-thirds of this transmission can be prevented by a course of AZT treatment. Given 400,000 potential perinatal infections (and assuming the minimal protocol outlined above would enjoy the two-thirds efficacy) this means that about 1,600,000 women could potentially be treated for a cost of $1.6 billion, and about 267,000 perinatal infections would thereby be avoided. The cost per infection avoided is thus $6,000- or about half that of the per-infection cost surmised from the AIDS Office's RFP. The differential may be in fact much greater, because

there would be economies of scale from such a vast Third World campaign, and

perinatal infection prevention is a one-time event, whereas the prevention work called for in San Francisco's RFP only provides an 18-month window of services to the at-risk population.

Needless to say, funds are not going to be found for a worldwide campaign to save those 267,000 babies, so the above comparisons are moot.

As regards perinatal transmission, the tale of the two Worlds for the year 1996 can readily be summarized: in the First World, a few thousand newborns will acquire HIV, mostly because dirty needles are being used or shared. In the Third World, several hundred thousand newborns will acquire HIV, almost all because ordinary men and women are living their heterosexual lives not very differently from others around them. Present trends point to big changes by 2001, oh yes: the former figure down to the hundreds, and the latter figure into the millions.

I find it an awesome emotional experience to visualize those two Worlds, living together today on the same planet.

(MidCity Numbers, October 1996)