Global AIDS 101

The Global HIV/AIDS Crisis Today

• An estimated 34.0 million people worldwide were infected with HIV/AIDS at the end of 2010.
• In 2010, 1.8 million people died due to HIV/AIDS, and another 2.7 million were newly infected.
• An estimated 68 percent (approximately 22.9 million people) of those infected were in sub-Saharan Africa [PDF, 214KB].
• In Asia [PDF, 204KB], an estimated 4.8 million people were living with HIV in 2010, including the 360,000 people who became newly infected.
• In Central and South America [PDF, 239KB], there were an estimated 1.5 million people living with HIV/AIDS in 2010; in North America and Western and Central Europe [PDF, 134KB], there were 2.2 million people living with HIV/AIDS.
• In sub-Saharan Africa, HIV/AIDS disproportionately affects women, who represent 59 percent of the region’s infected individuals. Worldwide, 17.0 million women are HIV positive.
• Worldwide, 3.4 million children under 15 are living with HIV/AIDS, and 390,000 were newly infected in 2010.

Basic Biology

The human immunodeficiency virus (HIV) is a simple virus that causes infection and serious illness in a complex way.

How HIV attacks the cell
First, HIV latches onto a specific primary “receptor” on the target cell’s surface called the CD4 receptor. Then, HIV effectively injects itself into the cell by fusing with the cell’s membrane and then passing through it. Once inside the cell, the virus breaks open and releases RNA and an enzyme called reverse transcriptase, which allows it to produce its viral DNA. The reverse transcriptase takes the coding in the viral RNA and makes viral DNA. The viral DNA is then integrated into the person’s normal DNA cell nucleus. Now the viral DNA can effectively hijack the cell’s production machinery to produce the various viral components. The viral components are then assembled into viruses that are released from the cell – potentially to go on and infect other cells.

Three things to remember:

• HIV attacks the immune system at the same time the immune system attacks it. The constant battle between the immune system and the HIV infection creates and destroys both virus and CD4 cells at a rapid rate.
• When HIV progresses, viral levels rise and CD4 levels fall. Measuring the number of CD4 cells (CD4 count) is one of the main ways of monitoring HIV disease progression.
• HIV does not cause death directly. Rather, the severely weakened immune system makes the person susceptible to other organisms that are easily fended off by the normal immune system.

Modes of Transmission and Course of Infection

HIV is spread by three main modes of transmission. It can be spread through unprotected sexual relations with the exchange of semen or vaginal secretions, blood-to-blood contact, and from a mother to her child.

Since HIV is such a fragile virus, it cannot survive on its own and therefore cannot be spread through air, water, food, toilet seats, insects, hugging, saliva, tears, or sweat.

Heterosexual sex is the most common mode of transmission worldwide. In addition, anal intercourse is especially risky for both partners, but particularly the receiving partner. The rectal mucosa is very vulnerable to trauma.

HIV is also spread through the sharing of needles or syringes, transfusion of contaminated blood, and needle-stick injuries from contaminated needles.

Mother-to-child transmission can occur at three different times: through the placenta during pregnancy, during delivery or labor itself, and through breastfeeding.

The course of HIV infection is divided into three phases:

• Early or Acute Phase – The initial phase lasts only a few weeks, and it is the time when the HIV infection rapidly replicates and the viral levels rise quite high. Flu-like symptoms occur in some people. Eventually, the immune system kicks in to lower the viral levels.
  
  
• Long Asymptomatic Phase – The second phase typically lasts 7 to 10 years. People don’t experience symptoms, but the virus is still in their body.
  
  
• Symptomatic/AIDS Phase – The final phase of HIV occurs when the virus begins to take its toll on the body, and CD4 levels drop. When this occurs, the body is susceptible to other infections and the severe symptoms of AIDS.

The high level of infectiousness in the first phase is most likely profoundly important in the spread of HIV, as one newly infected person may infect the next.

Basic Epidemiology of HIV

Prevalence is the result of cumulative incidence over the years. Since the early 1980s, global HIV prevalence has increased to around 33 million people.

There are two types of HIV epidemics: generalized and concentrated. A generalized epidemic is when the epidemic has spread into the general population. Generalized epidemics are largely confined to a little over a dozen countries in Eastern and Southern Africa, but these constitute the majority of worldwide infections. In most countries, HIV is largely concentrated among individuals at high risk, such as prostitutes, intravenous drug users, and men who have sex with men. A concentrated epidemic is when infections are mostly among these groups.

Certain factors can affect a person’s risk for HIV:

• Number of Sexual Partners – In certain high-prevalence epidemics, a considerable number of men and women have more than one fairly regular partner. Condom use is much less likely in such relationships. Because of this, these sexual networks appear to be extremely risky, with the potential for one newly infected person to infect a non-infected partner. Another important vehicle of transmission is commercial sex, especially in concentrated epidemics.
  
  
• Gender – General roles and inequalities make women especially vulnerable to HIV. Prevention efforts should portray positive male role models, discourage cross-generational sex and sex with multiple partners, promote partner communication, discourage coercive sex, and reduce gender inequalities in the law.
  
  
• Cross-generational Sex – Cross-generational sex, a relationship between an older man and a younger woman, puts young women at risk when they have relations with older, more experienced men. In fact, in Malawi, 8.4 percent of young women are infected with HIV as opposed to 2.4 percent of boys the same age.
  
  
• Urban Areas – Urban areas have a higher prevalence rate than their rural counterparts. An example is Kenya, where in 2003, its urban population had a prevalence rate of 10 percent, and the rural population had a prevalence rate of 5.6 percent.
  
  
• Wealth – Contrary to what most believe HIV actually increases markedly with household wealth. Much of the explanation for this relationship is due to the fact that people with more wealth tend to be urban.
  
  
• Alcohol – Alcohol can lead to an increased HIV risk by lowering inhibitions, providing situations where opportunity for risky sex is increased, and increasing gender-based violence and coercive sex. Knowing one’s limits and exercising good judgment are two ways to avoid risky situations that might expose a person to HIV.
  
  
• Concordant and Discordant Couples – There are three different outcomes for a couple who tests for HIV: concordant negative, where both are HIV negative; concordant positive, where both are HIV positive; and discordant, where one partner is HIV positive and the other is not.