AIDS: Back to School

Aliases: acquired immunodeficiency syndrome, AIDS

The 20th century was a veritable hit parade of medical breakthroughs: antibiotics were discovered in 1928, the polio vaccine was developed in 1952, and a suite of other vaccines were created that saved us from once life-threatening illnesses, such as rubella and tetanus. To top things off, smallpox was declared officially eradicated in 1980 (see my October post for more on smallpox). We were feeling a bit smug. That didn’t last long. In 1981, AIDS was identified. Over the last thirty-three years, the AIDS epidemic has taught us a great deal about disease, but it’s most important lesson may be that, despite our growing knowledge, there is still much to learn.

The initial outbreak of AIDS was terrifying, in part because we didn’t know what we were seeing. It was difficult to identify AIDS as a single unique disease, because people who develop AIDS don’t die from it. That seems impossible, but AIDS only weakens the body’s defenses, leaving patients vulnerable to infections that hit them while they’re down, taking advantage of their ravaged immune systems. Consequently, patients died of a range of other illnesses, which made linking the deaths more challenging. AIDS also appeared to come out of nowhere, because patients can seemingly remain healthy for over a decade after contracting the disease (see the Consequence section below). Unraveling the biology of AIDS has given us a crash course in the importance of retroviruses (rapidly evolving RNA viruses; HIV-1 evolves about one million times faster than mammalian DNA) and zoonotic diseases (diseases that emerge from non-human animal reservoirs; AIDS came from non-human primates)2.

AIDS has also delivered a brutal lesson in humility. Despite our best efforts, HIV (the virus that causes AIDS) has infected 60 million people and killed more than 25 million worldwide since it’s discovery2. In 2012, there were approximately 2.3 million new HIV cases and 35.3 million people were infected. The majority of these were in sub-Saharan Africa, where HIV afflicts 1 out of every 20 adults. Perhaps more than any other illness, AIDS has illustrated the importance of information. In the US alone, there are about 50,000 new HIV infections each year and about 1.1 million people are living with the virus- a shocking 16% of which do not know they have it1.

aids
Knowledge is power.

Cause: AIDS is caused by the human immunodeficiency virus (HIV), which is transmitted person-to-person through contact between the mucous membranes or damaged tissue of a healthy person and the bodily fluids (blood, semen, pre-seminal fluid, breast milk, and rectal and vaginal fluids) of an ill person. This most commonly occurs during sex; anal and vaginal sex are the highest risk behaviors for the spread of HIV. Sharing injection drug syringes is also high-risk. HIV is not spread by saliva, tears or sweat, and does not survive long outside the body, so it is not spread by environmental contamination. Unfortunately injury can be added to injury; there are multiple strains of HIV, and it is possible to be infected by more than one, resulting in a superinfection1.

Consequence: Most people do not immediately experience symptoms from an HIV infection; in fact, symptoms may not emerge for over a decade. Early symptoms sometimes occur 2 to 4 weeks after infection, and resemble the flu. This is the first stage of infection, called acute infection. The second stage, chronic HIV infection, is asymptomatic (symptomless), and may last several decades if the person is receiving treatment. Although they are not overtly ill, the HIV is still active, just reproducing at low levels. The third and final stage of an HIV infection is AIDS, when the patient’s CD4 cells (white blood cells that are a critical piece of the immune system) drop from the normal 500-1600 cells per cubic millimeter of blood to 200 cells/mm3, indicating that the immune system is badly damaged. Once this occurs, infections and infection-related cancers, collectively referred to as opportunistic illnesses, will afflict the ill person. Patients typically live 3 years after an AIDS diagnosis1.

Cure: Antiretroviral therapy (ART), a cocktail of antiretroviral drugs (medicine targeting retroviruses), is used to treat HIV. Although patients should be treated for related opportunistic illnesses, there is no treatment for AIDS. Despite the amazing medical advances since the discovery of HIV, 15,500 people died of AIDS in the US in 20101. The best defense truly is a good offense, and the best cure for AIDS remains good prevention. Use condoms (see my February post for more information). Get tested (but wait 6 weeks after the possible exposure, otherwise an infection may go undetected); it’s easy, relatively painless, and in most cases very cheap or free.

To find the testing center closest to you confidentially, text KNOWIT (566948) to or call 1-800-CDC-INFO (1-800-232-4636).

References

  1. HIV/AIDS. Centers for Disease Control and Prevention. 28 July 2014. Web. 16 September 2014. http://www.cdc.gov/hiv/basics/transmission.html
  1. Sharp, PM, & BH Hahn. (2011). Origins of HIV and AIDS Pandemic. Cold Spring Harbor Perspectives in Medicine.

Image source: The Stigma Project, http://www.thestigmaproject.org

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Suzi Claflin

I am a postdoctoral fellow studying chronic disease epidemiology.

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