Month: January 2005

Why is HIV/AIDS more prevalent in Africa than in America? This paper argues, based on statistical models, that it’s because of differences in how difficult it is to transmit HIV to a partner. All else being equal, an American who has sex with an HIV-positive American is much less likely to get infected than a Zambian who has sex with an HIV-positive Zambian. Therefore, the number of positive Zambians can increase at a much more rapid rate than the number of positive Americans.
There are a variety of reasons why. Poor nutrition weakens the typical African’s immune system and makes it harder for his/her body to prevent the virus from invading cells. The STDs of Africans are less likely to be treated, leaving them more likely to (grossness alert) have lesions or other unnatural openings down south. And there are a variety of other illnesses in southern Africa that impact the urogenital system — I’ve long suspected bilharzia is an HIV risk factor.
The strange thing about HIV is that it’s actually pretty hard to get if you’re healthy and having traditional heterosexual sex. Heterosexual transmission is rare: “Per-act infectivity in two studies was found to be low: 0.0005 and 0.0009 for male-to-female transmission, and 0.0003 and 0.0001 for female-to-male transmission.” In other words, it takes between 1,100 and 2,000 incidents of a healthy woman having unprotected sex with an HIV-positive man for one woman to be infected. The reverse path is even more rare: on average, it takes between 3,300 and 10,000 unprotected sex acts with an HIV-positive woman for a healthy man to be infected. But with STDs in the picture, those per-act infection rates skyrocket.
(Strangely, even with the gold standard of sexual transmission — receiving unprotected anal sex — it’s pretty hard to get HIV. “One recent study estimated the per-act risk of HIV infection from [unprotected receptive anal intercourse] with a partner who is HIV-positive at 0.82% (82 in 10,000).” Different studies produce different numbers, but they’re all in the same general ballpark.)
Anyway, all this is to say that if you can explain the geographic infection gap away just by looking at transmission rates, it’s awfully strong evidence that more focus should be put on remedies that can cut that transmission rate: better nutrition, aggressive STD treatments, etc. The good news is that a lot of that work is relatively cheap — cheaper than even the rapidly dropping cost of protease inhibitors and other anti-AIDS drugs.
More controversially, putting the blame on transmission rates also argues that changing sexual behavior isn’t nearly as useful as you might imagine. See page 55 of the paper, which compares American HIV infection rates (about 0.2 percent of adults) to sub-Saharan African rates (about 12.7 percent). If the U.S. suddenly had the same transmission rate as Africa — that is, if getting infected were as medically easy in America as it is in Africa — the U.S. infection rate would rocket up to 12.2 percent. But if U.S. patterns of sexual behavior were suddenly the same as Africa’s — which generally means more extramarital sex and less condom use, but less premarital sex — the American infection rate would barely budge. Or look at page 60, which models what African infection rates would do if you were able to reduce the ease of transmission by 20 percent versus what would happen if you could reduce all sexual activity by 20 percent. Transmission means more.
An enormous amount of the funding that goes into fighting AIDS in Africa is about behavioral change — primarily towards encouraging condom use and abstinence. Behavioral change is really, really hard to do — even just moving the needle on condom use a few percentage points. But this research would seem to indicate that money might be better put toward treating gonorrhea and chlamydia.
(Apologies to those of you who come to crabwalk.com just for the fart jokes.)

Marjorie Williams died Sunday. She kicked ass.

Bill Gates, teen heartthrob. Ick.
Joseph Forte tries to clean up his act. I’ve never seen an athlete plummet so quickly. He was the man at Carolina.
People with sexy voices have sex earlier and more often with more people. Also, they’re more likely to have pinky fingers of roughly equal length. Poor Diane Rehm — she must have horribly uneven fingers.

I owe you guys some good posts. Much exciting stuff going on in my life, workwise and otherwise, but I shan’t go into too much detail. Random thoughts:
– Am I the only person who, when seeing Paul Giamatti in a movie, thinks of Wallace Shawn? And vice versa? Not because of physical resemblance, although there’s some there. Primarily because they’re both sons of men who you might imagine expected non-Hollywood careers for their offspring. (A. Bartlett Giamatti, former president of Yale, and William Shawn, legendary New Yorker editor and man quoted on this site’s About page.)
– I know I’m more likely than most to get excited about the release of 544-page, lengthily-subtitled history books about obscure moments in Atlantic Canadian history. But I’m really excited about next month’s release of A Great and Noble Scheme: The Tragic Story of the Expulsion of the French Acadians from Their American Homeland, by Yale history prof John Mack Faragher. I’ve been interested in the 1755 expulsion for years (for obvious personal reasons, since it was my ancestors who were expelled), but I really look forward to a historian of Faragher’s rank cutting through some of the self-serving mysteries that cling to the events of 250 years ago.
– Mac geeks like myself are always trying to figure out what’s coming up from our favorite company. That’s mostly done through rumor sites — a dozen or more sites that chronicle leaks from Cupertino on what new products are coming down the pike. The best of these has long been Think Secret, which seems to clearly have the best sources and generally nails its predictions — so much so that it’s currently the target of a trade-secrets lawsuit by Apple.
Anyway, I mention all this because it turns out the guy who runs Think Secret is a 19-year-old kid. Who has been running Think Secret since he was 13. Sign this manchild up, news organizations of the future! (By the way, Apple’s lawsuit is bullshit and will go nowhere. Journalists can’t go to jail in this country for asking questions, thank heavens.)
– Heartaches of Journalist Bloggers, in Wired. Exhibits A through L of why I don’t blog about what I write about (other than to link to my stories).
– MP3s of live Neutral Milk Hotel from 1998. Sound quality’s okay, but it’s hard to remember sometimes how amazing NMH was there for a while.
– Vaguely ludicrous covers of the Velvet Underground’s White Light/White Heat by someone named Ergo Phizmiz.
– Random MP3s: Keleya, a kick-ass ’70s funk number from a West African James Brown disciple named Moussa Doumbia; The Muppet Show theme music sung in Hebrew; Bill Hicks railing on (the first) George Bush in 1992.

This story, from today’s front page, is in some ways the climax of all the other ones I’ve written lately:
AUSTIN