The Human Immunodeficiency Virus (HIV), which causes Aids, has created one of the world’s most devastating health problems.
Current evidence from genetic analysis of the virus suggests that HIV originated in Kinshasa in the 1920s, from a similar virus in monkeys and spread initially along railway routes in central Africa before spreading to distant regions of the world, leading eventually to the first reported cases of Aids in the United States in 1981. Since then more than 70-million people are estimated to have been infected with HIV and about 36-million people have died.
Right from the start, Aids grew to become not just a medical challenge but a challenge to the very fabric of society as ignorance, stigma and discrimination enhanced the spread of HIV at a time when thousands were dying daily. The first 25 years of the Aids epidemic saw many losing loved ones, hundreds of thousands become orphans and an unparalleled impact on communities. However, the past decade or so has seen a substantial decline in new HIV infections. Estimates from the Joint United Nations Programme on HIV and Aids indicate a 38% drop in the number of new HIV infections each year, from 3.4-million in 2001 to 2.1-million in 2013.
The decline in new HIV infections is a consequence of three things; a) expansion of Aids treatment globally, b) vigorous HIV prevention efforts and c) the usual natural course of an epidemic is to increase to a peak before declining, a cycle that can repeat itself many times if the epidemic is not brought under control.
One of the most impactful current interventions to reduce new infections is treatment. Drastic reductions in antiretroviral drug prices, coupled with the creation of organisations such as the Global Fund to Fight Aids, Tuberculosis and Malaria in 2002 and the President’s Emergency Plan for Aids Relief in 2004 made Aids treatment a reality for those most in need. By the end of 2012 an estimated 9.7-million people in low- and middle-income countries were receiving antiretroviral treatment (ART).
This impressive scale-up of ART is beginning to impact on the course of the HIV epidemic. In one rural South African community, for example, scale-up of ART between 2003 and 2011 has reduced the risk of acquiring HIV by 38%, while increasing life expectancy by 11.3 years.
Great strides have been made globally in preventing babies from contracting HIV infection. Transmission of HIV from mother-to-child has decreased by 58% over the 10-year period up to 2013. Providing antiretroviral treatment to HIV-positive pregnant women has averted more than 900000 new HIV infections among children across the world since 2009. In some parts of the world, mother-to-child transmission of HIV has been virtually eliminated. But despite this progress, it is still of concern that an estimated
240000 children became infected globally with HIV in 2013.
Scientific research in the last five years has led to the development of several new biomedical interventions that prevent HIV infection. In 2005, voluntary medical male circumcision was proven to reduce HIV acquisition in men by 54%. Scale-up of male circumcision from 12% in 2007 to 53% in 2010 in one South African community is estimated to have reduced new HIV infections by 61%. Since 2010, results from a number of clinical trials, which have demonstrated the effectiveness of antiretrovirals in HIV prevention, have transformed the HIV prevention landscape.
A vaginal gel containing the antiretroviral tenofovir, used before and after sex, reduced the risk of HIV and genital herpes infection in women. The tablet form of tenofovir or combinations of drugs with tenofovir, taken daily as pre-exposure prophylaxis (PrEP), reduced the risk of HIV in HIV-negative partners in discordant couples, men who have sex with men, at-risk men and women, and people who inject drugs. Daily PrEP for HIV prevention has been recommended for men who have sex with men by the World Health Organisation but adherence to the daily tablets is essential. Treatment of HIV-positive people with combination antiretrovirals to suppress their viral load has been shown to reduce the transmission of HIV to their sexual partners by an impressive 96%.
Despite these many achievements in scientific discovery, resource mobilisation, service delivery and political commitment, HIV remains a major global health challenge. In 2013, an estimated 35-million people globally were living with HIV and about 6 000 new HIV infections were acquired each day. Two-thirds of these infections were in Sub-Saharan Africa and one-third in young people between 15 and 24.
In most countries, even those with a declining overall prevalence, new HIV infections continue to occur at unacceptably high levels in many populations, such as young women, especially in Africa, sex workers, men who have sex with men, transgender individuals and people who inject drugs.
Sub-Saharan Africa accounts for just over 70% of all HIV infections, with young women having as much as eight-fold higher HIV rates than their male counterparts. Several factors contribute to this: vulnerability in young women in Africa, including older male partners who are unwilling to use condoms, high levels of intimate partner violence and high rates of other sexually transmitted infections. The scale of the HIV epidemic in these populations is generally poorly understood with many not being acknowledged at country level.
Continued success against HIV demands that each country identify, characterise and prioritise their highest risk groups. Disappointingly, many countries around the world still have laws that criminalise sex work, drug use, and same-sex relationships.
HIV prevention for these groups requires a different approach, as they are often hard to reach, marginalised, disempowered and stigmatised. In many instances there are structural obstacles preventing scale-up of HIV prevention interventions. For example, sex workers may not be able to access prevention programmes in a setting where sex work is illegal. Similarly, gender inequality and the threat of gender-based violence may be an obstacle for young women to insist that their partners use condoms. These obstacles highlight the importance of addressing broader social, legal and political impediments as an integral part of implementation programmes that scale up biomedical HIV prevention strategies.
Although mathematical models demonstrate that it is possible reduce the incidence of HIV so that it no longer represents a public health threat by using combinations of available interventions, achieving Aids control will not be a simple task and will require much more than just biomedical tools. A more detailed understanding of HIV transmission at a local level needs to be combined with renewed effort to address ongoing HIV transmission.
Concerted action at the local level should take note of past failures and build on local and global successes in implementing effective interventions to scale. Effective implementation will also need reinvigorated effort to address stigma and discrimination, integration of Aids into the broader social development agenda, and the strengthening of health systems and programmes. Research towards more effective interventions and delivery models, including an effective HIV vaccine and a cure also needs to continue.
Examples of other important scientific innovations needed to bring us closer to successful HIV prevention, include HIV prevention methods for women, a diagnostic for primary HIV infection, long-acting antiretroviral drugs, a point-of-care viral load diagnostic, and better treatment options for paediatric (newborn to age 18) patients.
Now more than ever, we cannot afford to lose the momentum. Good progress has been made. Now is not the time for complacency. With a renewed local and global effort, significant reductions in new HIV infections is within our grasp.
Salim S Abdool Karim is the director; Cheryl Baxter is a research associate; and Quarraisha Abdool Karim is the associate scientific director of the Centre for the AIDS Programme of Research in South Africa at the University of KwaZulu-Natal (Caprisa)