Does the HIV epidemic represent primarily a failure of the public health system--or is it more likely a result of failure on an individual level to take steps necessary to prevent infection?
HIV-1 (in green) budding from cultured lymphocyte. (Courtesy, Wikipedia)
Epidemics of transmissible infectious agents are particularly good at rapidly exposing weaknesses, inadequacies, and dysfunctionalities in public health systems.
This year, it was Ebola that demonstrated how ill-prepared the World Health Organization was for this epidemic, as well as (at least for now) the outright failure to contain the epidemic due to the lack of adequate public health infrastructure in many countries. Three decades earlier, it was HIV that exposed these same weaknesses. In the US and elsewhere, recognition of how HIV was transmitted led to the implementation of “Universal Precautions” against blood-borne pathogens in the 1980s. As a result, nosocomial transmissions of HIV are practically non-existent today.
Nevertheless-and despite tremendous advances in the treatment and management of HIV in the Americas and Western Europe-new HIV infections in these regions have not decreased year-after-year for over a decade. In much of Africa, the number of new HIV infections is actually increasing exponentially.
Of course, Ebola and HIV are very different viruses. In particular, HIV is transmitted primarily sexually, and does not rapidly kill its host. In fact, even in untreated HIV-infected individuals, the virus co-exists with its host for years without causing any signs or symptoms of disease. Consequently, there are many more opportunities for transmission of HIV than, at least historically, there has been for Ebola. But does the continued epidemic of HIV represent primarily a failure of the public health system, or is it more likely a result of failure on an individual level to take the steps necessary to prevent infection? Or, put another way, would substantial increases in funding at the federal, state, and local levels, targeted at our public health efforts, have any effect on reducing the number of HIV infections in the US?
Not surprisingly, the answer is hard to determine. There is almost complete agreement that funding for both the NIH and public health funding outside of the NIH has been flat or decreasing for 10 years or more. In the last decade, substantial increases in health funding for “public health”-related activities have only been seen in the areas of bioterrorism defense and emergency preparedness. And, despite recent calls for billions more in increased funding each year for the NIH, the reality is that competing priorities at every level will make it difficult to “find the money” to bring these proposals to fruition.
What we do know about public health efforts to control sexually-transmitted diseases is that they are expensive. For syphilis, gonorrhea, and HIV, much of the money is directed at “contact tracing,” which has not substantially reduced the number of new cases of any of these infections. For instance, San Francisco Public Health officials recognized an increasing number of cases of syphilis in the summer of 1999, predominately in men who had sex with men (MSM), and who had met their partners on the internet. Despite substantial increases in funding, as well as very creative approaches aimed at prevention (eg, advertising in targeted locations; increased screening efforts at street fairs, clubs, and bars), the epidemic continued well past 2004, the last year of the report.1
A recent article in Science reports on a blog post from researchers at the Center for Global Development in Washington, DC, in which they wrote that they “couldn’t find a single study with convincing data that showed how a large-scale intervention directly led to lower numbers of cases or deaths.” 2 An example they used was the more than US$10 billion dollars contributed since 2002 by well-off nations to fight the malaria epidemic. Controlled clinical trials had shown that mosquito nets reduced cases of, and deaths from, malaria. But in the “real world,” the researchers found that the nets often weren’t used. In addition, other factors, such as improved housing and economic outlook, and even changing weather patterns may have played some role in decreasing cases of malaria.
A new field of research-“impact evaluation”-seeks to determine how effective spending on various health care initiatives has been. For instance, the Global Fund and the US President’s Emergency Plan for AIDS Relief (PEPFAR) have spent more than a combined US$60 billion HIV/AIDS.2 Both have been criticized for their failure to assess their impact. Even though antiretroviral drugs have been made much more widely available as a result of the funding, lack of adherence, poor access to care, and lack of availability of many laboratory assays that we take for granted in the US (eg, HIV RNA monitoring; resistance testing) may have substantially lessened the impact of the monetary contributions.
In the US, important factors contributing to the ongoing HIV epidemic include:
1. High levels of HIV prevalence among urban MSM.
One study found that HIV prevalence among urban MSM averaged 17%, and was 29% in black MSM, and 40% among MSM who used injection drugs.3 These rates are as high as those seen country-wide in sub-Saharan Africa.
2. Poor access to care, especially in rural areas, leading to delays in diagnosis of HIV.
In other words, as is true in sub-Saharan Africa, high HIV prevalence rates in sexually active persons with suboptimal access to care is likely to continue to fuel the HIV epidemic in the US for many years to come. On the other hand, the US HIV Prevention Trials Network (HPTN) has an ongoing trial, HPTN 071 (PopART) of 21 large population clusters in Zambia and South Africa that is investigating whether the combination of voluntary home-based testing and counseling plus universal antiretroviral therapy (ART) for those found to be HIV-infected can reduce population-level HIV incidence.4 Mathematical modeling employed by the study team suggested, using “realistic” assumptions, that HIV incidence could be reduced by at least 60% in 3 years.
Whether such an impressive result can be achieved remains to be seen. In the meantime, I am left with the unavoidable conclusion that, at least for the foreseeable future in the US, the most effective means of reducing HIV incidence will employ the combination of earlier and more convenient voluntary testing of at-risk individuals, and treating those found to be HIV-infected with ART (treatment as prevention). In addition, all of us can only hope that messaging surrounding increased personal responsibility and HIV disease prevention will convince sufficient numbers of at-risk individuals that HIV remains a disease better prevented than treated. The role that public health facilities will play in this effort is unclear.