- Globally, the number of new cases of HIV infection and the number of deaths from AIDS-related illnesses are falling, but the declining trend is not consistent worldwide: the greatest burden of disease is in Africa.
- Heterosexual contact remains the major route of HIV transmission.
- Early diagnosis and antiretroviral therapy (ART) radically improves the prognosis for patients with HIV infection, giving them a near-normal life expectancy.
First recognized in 1981, the acquired immune deficiency syndrome (AIDS) and its causal agent (human immunodeficiency virus, HIV) has driven a significant proportion of research during the last three decades. These efforts have already provided plenty of information on the natural history of the infection and led to the development of effective antiretroviral therapy (ART), providing a means of controlling – but not curing – the disease.
Epidemiological estimates show that in 2016 more than a half (53%) of the 36.7 million people living with HIV were in eastern and southern Africa. The good news about HIV/AIDS is that the number of new cases is falling and the estimated decline was 11% between 2010 and 2016, leading also to a big reduction in the number of deaths from AIDS-related illnesses: 1 million deaths in 2016 compared with 1.9 million in 2005, with an overall 48% reduction in 11 years.
The declining trends can be accounted for by different factors including increases in HIV testing, increased uptake of ART and the availability of pre-exposure prophylaxis. Despite the common beliefs, the main route of HIV transmission remains heterosexual contact. Moreover, 9% of new HIV infections annually are in children, infected in utero, at birth or through breastfeeding. Molecular and genetic tests make early diagnosis possible, but the number of cases diagnosed at a late stage is still high especially among heterosexuals, increasing the risk of short-term mortality and onward transmission.
Symptomatic primary HIV or seroconversion illness occurs in approximately half of infected individuals because of high levels of circulating HIV-1 and the acute immune response, which begins 2 or 4 weeks after exposure and can resemble influenza, infectious mononucleosis or aseptic meningitis. After seroconversion, the CD4 count typically increases, but usually to a level below normal. The viral load stabilizes at a set point within approximately 6 weeks. Without therapy, the CD4 count eventually declines. At a count of 350 cells/µL, the individual becomes increasingly susceptible to pathogens. As the CD4 count declines further (µL), the patient can develop opportunistic infections or HIV-related malignancies. At CD4 counts µL, patients are at risk of disseminated and systemic infections.
From a therapeutic point of view, the five classes of ART have dramatically improved the prognosis of people infected with HIV, giving them a life expectancy similar to that of the general population. What’s the new challenge in the field? Among others, optimizing the management of adverse events related to ART in an ageing population of patients.