transmission

Even though we've talked over the last year about the new HIV infections rate (incidence) in 2006, I haven't given any thought to the issue of transmission--how many people actually transmit HIV to an HIV negative person every year? And what does the looking at the rate of transmission over the course of the epdemic tell us about what's working or not working with prevention, testing, treamtment or care efforts?

Well that's why we have smarty pants like David Holtgrave, PhD at the Bloomberg School of Public Health at the John Hopkins University. His study, which JAIDS released online ahead of the publication date, looks precisely at HIV transmission rates over the course of the epidemic. They conclude that the highest rates of transmission occurred in the early years of the epidemic--in the early/mid 80s, and then began to drop off at several different points, particularly from 1985-1986 (31.4-17.4), and 1990-1991 (11.7-6.6). By 2006, the transmission rate declined to 5.0.

In other words, 95% of all people with HIV did not transmit the virus to people who are HIV negative.The study goes on to explain the possible causes for this drop in transmissions:

The general decline in HIV transmission rates over time could be considered a rough measure of prevention success, in that even as prevalence grew over time incidence did not grow proportionately. HIV diagnosis is known to significantly reduce HIV risk behavior, and in the past decade, there has been an increasing emphasis on prevention programs for persons living with HIV that further reduce HIV risk behavior and 2006.

Another interesting thing Holtgrave and co-authors note is that AIDS drugs (anti-retrovirals) didn't have a grand impact on transmission rates, as transmission was declining long before ARVs were on the market. Could it be that marginalised communities with no access to treatment is where those transmission rates did not decrease? Could it be that the prison boom and/or Welfare Reform Act of 1996 (when prison construction peaked and we hit the 2 million prisoner mark for the first time) disrupt or change sexual networks enough to create new HIV transmissions in social networks where they had been stable? Holdgrave doesn't ask these questions, but notes that further research needs to happen to explain why ARVs do not seem to have significantly decreased transmission of HIV. But in a Q & A on Johns Hopkins' website, he addresses the impact of housing stability on HIV risk, and also says what he would do if he was AIDS Czar in the Obama Administration:

I think it is critical to address unmet HIV prevention needs in the U.S. As I testified recently before Congress, my wish for a five-year plan would be for $1.3 billion in prevention funding per year. I might front-load that a bit, so maybe it’s $1.6 billion in the first year, and so on. Over that five-year period, I estimate that as a nation we could reduce transmission by half—but we’d need that substantial investment. And if we really saw a drop in new infections, that higher level of funding might sunset in several years, so we wouldn’t necessarily have to continue to fund it at $1.3 billion per year.

Let's hope we're as lucky to have this come to fruition.

UPDATE: The CDC has published a factsheet and podast on HIV Transmission Rates in the US, based on the release of this data.

Last week, as I sat through a day and a half of CDC-sponsored expert consultation on anti-HIV therapy and transmission risk, listening to data on things like the biology of sexual transmission, pharmacology in the genital tract, viral loads and semen, and viral loads and vaginal secretions, the butt-cheeks of bias were spread before me and the gaping hole of neglect revealed.

It’s not like I didn’t know this already.  I subscribe and contribute to lifelube.org, I’m a member of the International Rectal Microbicide Advocates (IRMA), and I’m an active member of CHAMP’s Prevention Research Advocacy Working Group (PRAWG).  But frankly my ass is chapped.  Hearing one presenter casually refer to anal intercourse as having a twenty-fold higher transmission risk than vaginal intercourse and others repeatedly quip that there is little or no corresponding data regarding rectal / anal anything, I had a barely resistible urge to bend over and moon the podium, screaming.  read more »