Human immunodeficiency virus (HIV) is a retrovirus that infects cells of the immune system, destroying or impairing their function. As the infection progresses, the immune system becomes weaker, and the infected person becomes more susceptible to other infections.
It can take as long as 15 years for a person infected with HIV to develop acquired immunodeficiency syndrome (AIDS), the most advanced stage of HIV; antiretroviral drugs can slow down the process even further.
Disease trends
The number of HIV-incident cases will increase by 9.7% over the next decade in the ten major markets (Brazil, China, France, Germany, India, Italy, Japan, Spain, the UK and the US), from 276,590 in 2012 to 303,365 in 2022.
During this period, India is expected to have the largest number of HIV-incident cases. It reported 123,269 new cases in 2012, and this is expected to grow by 17.3% to 144,642 in 2022. This forecast is attributed to the population growth among people aged 15-49 years, the age group at the highest risk of contracting HIV.
Co-infections with the hepatitis C virus (HCV) and tuberculosis (TB) will continue to impose a burden on people living with HIV in the ten major markets. There were 170,388 cases of HIV/HCV co-infection in the five EU countries, with 41% in Spain (this is directly related to the number of injection drug users in the country). Approximately 700,000 cases of TB were found among prevalent cases of HIV in the ten major markets in 2012. More than 99% of all HIV-prevalent cases with concomitant TB infections will be in the emerging markets.
There were more than 2.26 million HIV-prevalent cases also on antiretroviral therapy in 2012. The US has the largest number of people living with HIV on antiretroviral therapy, almost 900,000.
Risk factors and comorbidities
HIV is transmitted through unprotected intercourse (oral, vaginal or anal); contaminated blood transfusions, blood products and medical equipment, including needles and surgical instruments; and from mother-to-child during pregnancy, delivery or breastfeeding. Disease-prevention strategies focus on reducing or eliminating contact with infected bodily fluids. The table opposite lists the most common prevention strategies to reduce the transmission of HIV.
Several diseases occur frequently with HIV as the disease progresses to AIDS. Because these are part of the disease progression, they are not considered comorbid conditions. However, HCV and TB are the most common co-infections in people with HIV, as the modes of transmission are similar.
Global trends
Trends in incidence, prevalence and mortality have changed over the years due to factors such as improved treatment and screening programmes aimed at the early detection of infection. The HIV pandemic started to decline in 2007 in most countries due to public policy campaigns focused on disease prevention by: promoting condom use, monogamy and abstinence from sex; discouraging needle sharing; and supporting global safety procedures for bloodborne pathogens.
At the end of 2010, 34 million people were living with HIV around the world, an increase of 17% from 2001. Of these, 16.8 million are women and 3.4 million are under the age of 15 years. An estimated 2.7 million new HIV infections were reported in 2010, a 21% decrease from the height of the HIV pandemic in 1997. The estimated number of AIDS-related deaths peaked in 2004 at 2.1 million and fell to 1.8 million in 2009. This is partly due to increased access to antiretroviral drugs in low-income countries.
Despite an overall drop in new infections, the number of people living with HIV continues to grow worldwide because antiretroviral therapy usage is prolonging their survival.
Antibody tests, such as enzyme-linked immunosorbent assay (ELISA) or rapid test, are the most frequently used to diagnose HIV. Positive antibody tests are then confirmed with western blot; however, in resource-poor settings, a second rapid test or ELISA is sufficient to confirm a positive result.
Outlook
The global incidence of HIV has stabilised in recent years and has begun to decline in most countries. However the number of new infections among high-risk groups will continue to drive the increase in incident cases in the ten major markets. As surveillance systems and reporting methods are refined, and become more transparent in China and India, the understanding of HIV epidemiology in these emerging markets will also improve.
There were 280,000 incident cases of HIV in the ten major markets in 2012. This will grow by approximately 10% over the next decade to 300,000. While such a forecast may seem counter-intuitive because of the disease’s recent stabilisation, the projected increase will be driven mainly by the expected increase of incident cases in Brazil, China and India.
Brazil has adapted HIV/AIDS prevention programmes aimed at controlling disease transmission among those most at risk in that country – young adults, injection drug users and sex workers. However, the country’s projected population increase forecasted in adults aged 30-34, who have the highest HIV-incidence rates, will drive the expected rise in incident cases of HIV over the next decade.
If India and China adopt prevention programmes similar to Brazil, considered a model of HIV prevention for the developing world, the number of incident cases could fall, as high-risk groups become the focus of targeted prevention strategies. Furthermore, if India and China were to provide free antiretroviral therapy to people living with HIV, the number of prevalent cases in these markets would increase, more so than predicted in this forecast.
A high number of pregnant women with HIV in India and China is expected, so the amount of paediatric cases in these markets will fall or be eliminated if these markets adopted a programme similar to Brazil’s. However, the number of people living with HIV on antiretroviral therapy is already high in China, so the rate of mother-to-child transmission is likely to be low. At this time, it is difficult to determine the quantity of paediatric HIV cases in China due to the issues surrounding the transparency of the HIV disease burden in that country.
Although all countries covered in this report have introduced preventive programmes and government-led interventions targeting high-risk HIV populations, the burden of HIV is expected to continue. Sustained levels of high-risk behaviour along with population growth make it challenging to forecast how much of a burden this will be. The number of HIV-prevalent cases will reach nearly 15% over the next decade, rising from 5.4 million in 2012 to 6.2 million in the ten major markets. This increase can be attributed to the growing population over the forecast period and improved access to antiretroviral therapy.
Because the prognosis of people with HIV has improved dramatically over time with the introduction of improved antiretroviral therapies, the number of people living with HIV is expected to rise greatly over the next decade. If access to medication improves in all markets, the number of people living with HIV will rise more rapidly than this forecast predicts.
