The Epidemiology of HIV-1 Transmitted Drug Resistance

The human immunodeficiency virus (HIV) was first discovered in 1983. In 2009, it was estimated that 33.3 (31.4 -35.3) million individuals are infected with HIV worldwide. In that year 1.8 (1.6-2.1) million people died from HIV. Although the virus continues to spread, the number of new infections has fallen from an estimated 3.2 (3.0 -3.5) million in 1997 to 2.6 (2.3 – 2.8) million in 2009. There are several explanations for this decrease. First, the use of antiretrovirals has slowed down the epidemic by suppressing viral replication and thereby the HIV RNA load [2]. This RNA load is a key factor in determining transmissibility of HIV. Second, sexual risk behaviour has decreased in most countries. Third, HIV prevalence follows an ‘S’ curve, like any infectious disease where it start slowly and gradually. In the final phase of the epidemic, people are either no longer infectious (due to effective treatment) or deaths outnumber new cases, so that the total number alive and infected passes its peak and begin to decline or reach a plateau. The majority of new HIV infections continue to occur in sub-Saharan Africa. Here, an estimated 1.8 (1.6 -2.0) million people were newly infected in 2009 and 22.5 million (20.9 -24.2) people were living with HIV in this region (figure 1). In Europe, the HIV-1 epidemic is much smaller, with an estimated 130,000 (110,000-160,000) newly infected in Western and Central Europe in 2009. This results in 820,000 (720,000-910,000) individuals living with HIV-1 and a prevalence of 0.2% in this region.