Over the last 3–5 years, the pandemic of HIV/AIDS appears to have reached a plateau for prevalence rates in most areas of the world. In all major regions except sub-Saharan Africa, saturation levels for HIV prevalence are below 1%. In sub-Saharan Africa, the WHO estimates are about 5% for adults aged 15–49. However, within sub-Saharan Africa, southern Africa has a much higher rate, about 18%, while the rest of sub-Saharan Africa is 3–4%.
Why are “saturation-level” HIV prevalence rates about 5-fold higher in southern Africa? Behavioral practices, differences in human genetics, and different viruses are all theoretical possibilities. The HIV-1C which causes the southern Africa epidemic has several features that appear to make it different. These include different rates of genomic variation and different patterns of drug-resistant mutations.
About one quarter of HIV-1C-infected adults show a prolonged pattern of high viral load (VL) following infection. Because high VL is associated with transmissibility, this suggests that such individuals may be “hypertransmitters” who are more highly infectious to their sexual contacts. Antiretroviral drug treatment (ART) dramatically decreases VL and HIV transmission. It then follows that to decrease transmission among adults, targeting those with high VL may reap the greatest benefit. Our current project in Mochudi, Botswana, utilizes this approach while incorporating HIV envelope sequence fingerprinting as a tag to monitor transmission.