Archive for the ‘HIV/AIDS’Category

African population density

I was recently struck by differences in population density: Northern Nigeria’s Kano state has an official population of ~10 million, whereas the entire country of Zambia has 13.5. Zambia’s land area, meanwhile, is also about 35 times that of Kano.

So I started looking around for a nice map of population density in Africa. The best I found was this one via UNEP:

And here’s a higher resolution version.

Some of the most striking concentrations are along the Mediterranean coast, the Nile basin, the Ethiopian plateau, and around Lake Victoria. (I’d love to track down the data behind this map but haven’t had time.)

A good map can change how you think. If you’re used to seeing maps that have country-level estimates of disease prevalence, for instance, you miss variations at the subnational level. This is often for good reason, as the subnational data is often even spottier than the national estimates. But another thing you miss is a sense of absolute population numbers, because looking at a map it’s much easier to see countries by their areas rather than their populations, which for matters of health and other measures of human well-being is generally what we care about. There are some cool maps that do this but they inevitably lose their geographic accuracy.


07 2013

Why did HIV decline in Uganda?

That’s the title of an October 2012 paper (PDF) by Marcella Alsan and David Cutler, and a longstanding, much-debated question in global health circles . Here’s the abstract:

Uganda is widely viewed as a public health success for curtailing its HIV/AIDS epidemic in the early 1990s. To investigate the factors contributing to this decline, we build a model of HIV transmission. Calibration of the model indicates that reduced pre-marital sexual activity among young women was the most important factor in the decline. We next explore what led young women to change their behavior. The period of rapid HIV decline coincided with a dramatic rise in girls’ secondary school enrollment. We instrument for this enrollment with distance to school, conditional on a rich set of demographic and locational controls, including distance to market center. We find that girls’ enrollment in secondary education significantly increased the likelihood of abstaining from sex. Using a triple-difference estimator, we find that some of the schooling increase among young women was in response to a 1990 affirmative action policy giving women an advantage over men on University applications. Our findings suggest that one-third of the 14 percentage point decline in HIV among young women and approximately one-fifth of the overall HIV decline can be attributed to this gender-targeted education policy.

This paper won’t settle the debate over why HIV prevalence declined in Uganda, but I think it’s interesting both for its results and the methodology. I particularly like the bit on using distance from schools and from market center in this way, the idea being that they’re trying to measure the effect of proximity to schools while controlling for the fact that schools are likely to be closer to the center of town in the first place.

The same paper was previously published as an NBER working paper in 2010, and it looks to me as though the addition of those distance-to-market controls was the main change since then. [Pro nerd tip: to figure out what changed between two PDFs, convert them to Word via, save the files, and use the ‘Compare > two versions of a document’ feature in the Review pane in Word.]

Also, a tip of the hat to Chris Blattman, who earlier highlighted Alsan’s fascinating paper (PDF) on TseTse flies. I was impressed by the amount of biology in the tsetse fly paper; a level of engagement with non-economic literature that I thought was both welcome and unusual for an economics paper. Then I realized it makes sense given that the author has an MD, an MPH, and a PhD in economics. Now I feel inadequate.


01 2013


I highly recommend Patient Zero, the  latest episode of the podcast RadioLab. It covers Typhoid Mary, the origin of HIV, and the diffusion of ideas. Evocative as always, but what I like the most is how they add new information to stories you think you know. For one, you really feel sorry for Mary. And I’ve read quite a bit on the origin of HIV (a great way to learn more about phylogenetics!) but RadioLab takes it back even further and highlights some research I hadn’t seen.

Related: I haven’t read it yet, but Tyler Cowen really likes Jacques Pepin’s new book, The Origin of AIDS more happy reading for Christmas break.


11 2011

The battle for hearts and minds

A major difference between the public health approach and the beliefs and strategies underlying fields such as human rights or medicine is that public health concerns the prioritization of limited resources. There is a limited pie. Even if you believe that pie can be expanded (it can, at times), it cannot be expanded infinitely, and so at some point in the policy process someone has to make a decision about how to prioritize the resources at hand.

This traditional public health approach overlaps with and gets blurred into human rights and medicine and politics such that the value judgments underlying different claims aren’t always apparent. We have a certain number of interventions that are known to work — they save lives and reduce suffering — but we don’t have enough resources to do all of those things in every place that needs them. If we choose option A, some people will be saved or helped, and some will die. If we choose option B, a different number of people will be saved or helped, and some other group of people will die. The discussion of who will be saved is often explicit, while the discussion of the opportunity cost, those who will not be saved is almost always lacking. Both groups are abstract, but the opportunity cost group is usually more abstract than the people you’re trying to help. These are generalities of course, and in reality there is uncertainty built into the claims about just how many lives could be saved or improved with any one approach.

The problem is this: pretty much everything we do in global health is good. Sure, we can argue specifics and there are glaring examples to the contrary, but for the most part we all want to save lives, prevent suffering, and improve health. No one is seriously against successful interventions when they stand alone: no one thinks people with HIV shouldn’t get antiretrovirals, or children with diarrhea shouldn’t get oral rehydration therapy. Rather, they may oppose spending money on HIV instead of on childhood diarrhea (or in reality, vice versa). Who is comfortable with making an argument against preventing childhood burns? Being against treating horrific cancers? Any takers? So we all argue for something that is good, and avoid the messy discussions of trade-offs.

Thus, much of the conflict in the global health fields is about spending money on X intervention versus intervention or approach Y. Or, better yet, traditional and known intervention A versus new and sexy and unproven-at-scale approach B. I don’t think I’d want to live in a world where all health decisions are made entirely by cost-benefit analysis, nor would I want to live in a world where all decisions on care and policy are made from a rights-based approach — both approaches result in absurdities when taken to their extremes and to the neglect of each other. My impression is that most professionals in global health draw insight from both poles, so that individuals fall somewhere on a continuum and disagree more with others who are furthest away. The tension exists not just between differing camps but within all of us who feel torn by hard choices.

So the differences between the mostly utilitarian public health old-guard and the more recent crop of rights-driven global health advocates aren’t always clear-cut, and they often talk right past each other … or they just work at different organizations, teach at different schools and attend different conferences so they won’t have to talk to each other. To some extent they’re fundraising from different audiences, but they also end up advocating that the same resources — often a slice of the US global health budget — get spent on their priorities. These tensions usually simmer under the surface or get coated in academic-speak, but sometimes they come out. Which brings me to an anecdote to leaven my generalities:

A few months ago I was having a private conversation with a professor, one who leans a bit towards the cost-benefit side of the continuum with a dose of contrarianism thrown in for good measure. Paul Farmer came up — I don’t remember how. I paraphrase:

Resource allocation is the central dilemma in public health. Period. If people don’t get that, they’re not public health. Paul Farmer? Fuck Paul Farmer. He just doesn’t get it.

You won’t hear that in a lecture or in a public speech, but it’s there. I’ve heard similar sentiments from the other side of the spectrum, those who see the number-crunching cost-benefiteers as soulless automatons who block the poor from getting the care they need.

These dilemmas are not going away any time soon. But I think being conscious of them and striving to be explicit about how our own values and biases shape our research and advocacy will help us to collectively reach a balance of heart and mind that makes more sense to everyone.

HIV/AIDS is one of the areas of global health where the raw passion of the heart most conflicts with the terrible dearth of resources we have to fight the demon. Decisions have ugly consequences either way you choose, and, rightly or wrongly, dispassionate research is often anything but. The recent news that pre-exposure prophylaxis (PrEP) can prevent HIV acquisition in sero-discordant heterosexual couples is huge in the news right now. Elizabeth Pisani (epidemiologist and author of The Wisdom of Whores) hits the nail on the head in this recent blog post. She notes that there are voices clamoring for widespread scale-up of PrEP — treating the HIV negative partner — but that PrEP prevents infection in 60% of cases while treating the HIV-positive partner cuts infection by 96%. Continuing:

That leaves us with the question: who should get PReP? Right now, there are not enough antiretrovirals to go around to treat all the sick people who need treatment. If we’re going to use them selectively for prevention, we should start with the most effective use, which appears to be early treatment of the infected partner in discordant couples. We could also give them to people who aren’t in a couple but who know that they’re likely to get around a bit and might want to stay safe without using condoms. That’s potentially a lot of people; it will stretch our purses. But more than that, it will stretch our political will.

So who is PReP for? We’ve got a better option for discordant couples. We’re not going to want to give it to randy adolescents. We know it works for gay men, but some of the countries where the trials took place would rather thump or jail gay men than protect their sexual health.[…] But I think we would be unwise to rush around talking about massive roll-out of PReP before we actually figure out who it works for in the real world.

Treating people with HIV is good. Preventing infection via treatment is good. Prevention infection via PrEP is good (assuming it doesn’t breed more drug resistant strains and make it harder to treat everyone… but that’s another story). But most voices in the debate have an agenda and are pushing for one thing above the rest. One of them — or a balance of them — is right, but you have to understand their values before that can be discerned. And I think many people in global health don’t even think explicitly about their own values, such as the mix of cost-benefit and rights-based approaches they find most appealing. Rather, we all want to promote whatever we’re working on that the moment. After all, it’s all good.


07 2011

History refresh: AZT and ethics

A professor pointed me to this online history and ethics lesson from the Harvard Kennedy School’s Program on Ethical Issues in International Research: The Debate Over Clinical Trials of AZT to Prevent Mother-to-Infant Transmission of HIV in Developing Nations. It’s surprisingly readable, and the issues debated are surprisingly current.

In 1994, researchers in the US and France announced stunning news of a rare victory in the battle against the AIDS pandemic. Studies conducted in both countries had shown conclusively that a regimen of the drug AZT, administered prenatally to HIV-positive pregnant women and then to their babies after birth, reduced the rate of mother-to-infant transmission of HIV by fully two-thirds. The results of the clinical trials constituted “one of the most dramatic discoveries of the AIDS epidemic,” the New York Times declared, and one of the most heartening as well.

The new regimen–known by its study name, AIDS Clinical Trials Group (ACTG) 076 or, often, simply “076”–offered the epidemic’s most vulnerable targets, newborns, their best hope thus far of a healthy childhood and a normal life span. The number of infants who might benefit from this research was significant: according to World Health Organization (WHO) figures, as many as five to ten million children born between 1990-2000 would be infected with HIV. In the mid-1990s, it was estimated that HIV-infected infants were being born at the rate of 1,000 a day worldwide.

So impressive were the findings of ACTG 076–and so substantial the difference in the transmission rate between subjects given AZT and those given a placebo (eight percent versus 25 percent)–that the clinical trials, which were still ongoing, were stopped early, and all participants in the studies were treated with AZT. In June 1994, after reviewing the study results, the US Public Health Service recommended that the 076 regimen be administered to HIV-infected pregnant women in the US as standard treatment to prevent transmission of the virus.

But while 076 was hailed as a major breakthrough, the celebration was somewhat muted. For a variety of reasons, the new treatment regimen would not likely reach those who most desperately needed it: pregnant women in the developing nations of the world and, most particularly, sub-Saharan Africa, where AIDS was wreaking devastation on a scale unimagined in the West.

I think one reason why graduate school can be so overwhelming is that you’re trying to learn the basic technical skills of a field or subfield, and also playing catch-up on everything that’s been written on your field, ever. True, some of it’s outdated, and there are reviews that bring you up to speed on questions that are basically settled. But there’s a lot of history that gets lost in the shuttle, and it’s easy to forget that something was once controversial. Something as universally agreed upon today as using antiretrovirals to prevent mother-to-child transmission of HIV was once the subject of massive, heart-wrenching debate. I tend to wax pessimistic and think we’re doomed to repeat the mistakes of the past regardless of whether we know our history, because we either can’t agree on what the mistakes of the past were, or because past conflicts represent unavoidable differences of opinion, certainty, and power. But getting a quick refresher on the history of a is valuable because it puts current debates in perspective.


02 2011