The number of identified drug resistant HIV strains is increasing steadily: from 80 documented strains in 2007 to 93 documented strains in 2008.(1) The direct and indirect health costs of drug resistance include: the need for increasingly expensive second and third line drugs, the transmission and spread of drug resistant virus within communities, and the ongoing need for research and development of new drugs and vaccine options.
In early 2010, the Journal of Science published new research into the prevalence and implications of drug resistance in San Francisco. People living with HIV in San Francisco have been using ARVs extensively since the 1980’s. A team of scientists from the University of California, University of Tennessee and University of Ottawa created a mathematical model to track the transmission of multiple strains of HIV and analyzed the data. The results predict a wave of drug resistant strains emerging over the next 5 years:
“Our modeling shows that 60% of the currently circulating ARV-resistant strains in San Francisco are capable of causing self-sustaining epidemics, because each individual infected with one of these strains can cause, on average, more than one new resistant infection. It is possible that a new wave of ARV-resistant strains that pose a substantial threat to global public health is emerging” (2)The model was applied to San Francisco, but the same predictions are made for other parts of the world where large scale treatment programs are rolling out. According to Sally Blower, director of UCLA's Center for Biomedical Modeling, "San Francisco is like the canary in the mine. In fact, the most significant implications of our work are for countries where treatment is just being rolled out". (3)
Not surprisingly, those at the frontlines of HIV treatment programs in hyper-endemic areas confirm increasing rates of drug resistance. In South Africa, where free ARVs have been available for 6 years, health care providers are describing high rates of treatment failure caused by drug resistance and an inability to offer their patients alternatives. According to one doctor, "For the first two or three years I was not seeing it. It was rare; now it is really daily”. (4)
In many parts of the developing world, the available supply of anti-HIV treatment consists of what are known as first generation ARVs. First generation ARVs cost less, but are not as effective at controlling HIV as the later generation medications available in resource-rich areas. Unlike newer and more expensive therapies, people on first generation ARVs can develop drug-resistance much more quickly - with only a single mutation of viral genetic code in some cases. To avoid resistance, people living with HIV must have access to an uninterrupted and lifelong supply of ARVs.
Furthermore, many clinics and health centres in the developing world do not have the resources to monitor viral load or perform pre-therapy resistance testing. Consequently, treatment failure caused by drug resistance is often a game of wait and see. Coupled with wide-spread speculation about a lack of ongoing political commitment to HIV/AIDS funding, the ability to provide a sustainable and effective supply of anti-HIV therapy to the developing world is in jeopardy.
Sources:
- The World Health Organization 2009 List of Mutations for Surveillance of Transmitted Drug Resistant HIV Strains Retrieved Feb 18, 2010 from http://hivdb.stanford.edu/pages/WHOResistanceList.html
- Evolutionary Dynamics of Complex Networks of HIV Drug-Resistant Strains: The Case of San Francisco. Retrieved Feb 5, 2010 from http://www.sciencemag.org/cgi/content/abstract/327/5966/697
- New Study Raises Concerns About HIV-Drug Resistance. Retrieved Feb 17, 2010 from http://www.time.com/time/health/article/0,8599,1953718,00.html
- In South Africa, Drug resistant HIV Emerging. Retrieved February 9, 2010 from
http://www.msnbc.msn.com/id/34624393/ns/health-aids//
0 comments:
Post a Comment