Charles John Palenik, MS, PhD
The most devastating disease humankind has ever faced is HIV/AIDS. Since the beginning of the HIV epidemic, almost 70 million people have been infected. Currently, 42 million persons are thought to be living with HIV/AIDS. Over 95 percent of these people live in the developing world. Each day, approximately 15,000 individuals become infected, while 10,000 die. HIV/AIDS has caused the life expectancy to drop in some countries from 65 to 36 years. Almost 50 percent of infections today are among women and young people from 15 to 24 years old. The result is that more than 14 million children have been orphaned.
There have been 868,510 cases of AIDS reported in the United States. Approximately 57 percent have died. The prevalence of AIDS in the United States, however, has increased steadily over time. More people with AIDS are living longer than in the past. Officially reported cases of HIV infection (but not AIDS) number 174,026. However, many people are unaware of their infection because they have not been tested. A surprising number become aware only after seeking treatment for disease-associated symptoms. An estimated 800,000 to 900,000 persons are living with HIV in the United States, with approximately 40,000 new infections each year.
In the summer of 1981, two reports indicated clusters of Pneumocystis carinii pneumonia (PCP) combined with severe immune depletion of T cells. The process we now know as AIDS had begun. Today, the fungus that causes human PCP is called Pneumocystis jiroveci. In the early days, most AIDS patients died within 24 months. Treatment was limited to controlling multiple, unique, and devastating opportunistic infections commonly present. Lacking diagnostic tests, only clinically based diagnoses could be used, such as the presence of certain opportunistic infections and Kaposi sarcoma without a history of immunosuppression or known immune deficiency.
The first breakthrough occurred in 1983 with the observation of viral particles budding out of cultured cells collected from a lymph node biopsy of a person with generalized lymphadenopathy. Researchers reasoned that generalized lymphadenopathy should precede the onset of AIDS, and might represent a significant immune response to infection. Thus, the causative virus might be more readily detected in affected nodes. The assumption proved correct. Major developments would quickly follow.
Within months, the viral genome had been cloned and sequenced. By early 1984, the virus had been detected in a number of persons with AIDS, including gay men, twin hemophiliac brothers, and a heterosexual couple. Large amounts of viral particles could be generated in special lines of T cells, and sufficient viral components collected. In 1985, these antigens proved useful in the development and implementation of a blood-screening antibody test for the presence of HIV.
This discovery also gave hope for the generation of antiretroviral therapies. In 1987, the FDA approved the first HIV/AIDS therapeutic agent, Zidovudine (AZT, ZDV, Retrovir). Zidovudine is a nucleotide analog that inhibits HIV reverse transcriptase. HIV is a single-stranded RNA virus. Upon entrance into the host cell, the RNA must be converted to DNA. A viral enzyme, reverse transcriptase, accomplishes this. Zidovudine is still used today and often is paired with other drugs.
HIV-infected persons are now living longer. More effective combination antiretroviral therapy (highly active antiretroviral therapy or HAART) is available. Instead of a quick death sentence where proper therapy is available, AIDS has been transformed into a treatable and somewhat manageable chronic affliction in the developed world. Despite elevated costs, drug side effects, and viral resistance, each therapeutic advancement lengthens the average lifespan after infection.
By 2002, HAART had led to an important mode of disease prevention. In the developed world, perinatal transmission of HIV (mother to fetus) now can be prevented in almost 99 percent of cases.
The situation is totally different for the vast majority of HIV/AIDS patients, with an alarming disparity in access to effective antiretroviral therapy. Significant political and economic stumbling blocks remain. In the end, the greatest intervention vehicle will be the development of an effective HIV vaccine.
OSAP is the leading source for infection control and human safety and health information in dentistry. A search of the OSAP Web site (www.osap.org) will provide more than 350 links on the topic of HIV/AIDS.
Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik has authored numerous articles, book chapters, and monographs, and is the co-author of the popular Infection Control and Management of Hazardous Materials for the Dental Team. He serves on the Executive Board of OSAP, dentistry's resource for infection control and safety.Questions about this article or any infection-control issue may be directed to [email protected].
