Aids As A Medical Problem

How big a medical problem is AIDS? As 2005 drew to a close, the World Health Organization estimated that more than 40 million people worldwide were HIV infected or had full-blown AIDS. At least 25 million have already died. Fourteen thousand new AIDS

cases are added each day. Ninety-five percent of HIV-infected individuals worldwide are heterosexual, and 50% are women. In developing countries, only about one in five infected persons receives treatment. All but a handful of these people will die of their disease; two-thirds of all the people ever infected with HIV have already died. AIDS is now the number one cause of death by infectious disease and the fourth leading disease cause of death throughout the world.

The overall shape of the HIV/AIDS pandemic in the United States is shown in Figure 8.1. Currently more than 1 million people in the United States are HIV infected or have frank AIDS. Only about a third of those infected are aware they are infected. Three-quarters of affected individuals are male, and half of those are black. Male homosexuals now account for less than half of existing cases. Current estimates for new cases range between 40,000 and 60,000 annually.

How do we make sense of numbers like these? What sort of perspective can we put them into? On the one hand, AIDS hasn't

200,000

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50,000

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50,000

figure 8.1

The HIV/AIDS pandemic in the United States.

figure 8.1

The HIV/AIDS pandemic in the United States.

yet come close to something like smallpox or hepatitis B as a killer of human beings on a historical scale. It is coming close to, and may have already surpassed, the influenza epidemic that swept 30 million human beings from the face of the earth just after World War I. What is so frightening about AIDS is the speed with which it is spreading, the incredible rate of increase in the number of cases diagnosed each year, with absolutely no cure in sight.

HIV, which is passed almost exclusively by exchange of body fluids, infects, and causes a gradual loss of, CD4 helper T cells in infected individuals. When the level of circulating CD4 T cells falls below roughly half the normal value, HIV-infected individuals begin experiencing the symptoms of frank AIDS, including infection by external pathogens and by internal opportunistic pathogens.

There are currently 18 drugs approved by the Food and Drug Administration (FDA) for treating AIDS (see Table 8.1), used alone or in various combinations. They fall into four categories: nucleo-side analogs, reverse transcriptase inhibitors, protease inhibitors, and a fairly new category, fusion inhibitors.1 We will see how these drugs work in a moment. These drugs can be enormously expensive, barely within the capacity of industrialized medical care systems to fund, and out of the question, at least at market prices, for developing or third-world countries.

Current standard therapy in the United States and other industrialized countries is something called HAART (highly active antiretroviral therapy). This consists of a combination of at least two reverse transcriptase (including nucleoside analogs) inhibitors, plus a protease inhibitor. Slight variations of this formula are also possible. The idea is to force the virus to mutate to multiple drugs at the same time in order to reproduce, which is much

1. Nucleoside analogs are in fact also reverse transcriptase inhibitors, so there are only four distinct categories. But for historical reasons, the two drug types are usually referred to separately.

table 8.1

Current Drug Therapy for AIDS

table 8.1

Current Drug Therapy for AIDS

Drug

Action

Approved

Cost/year

Zidovudine (AZT)

Nucleoside analog

March 1987

$4,300

Didanosine (ddI)

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