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Author(s): Gregory L. Vogt, EdD, and Nancy P. Moreno, PhD.

Trailing the Pandemic

Content Advisory
Depending upon students' grade and maturity levels, the essay, ”Trailing the Pandemic," may be used as teacher background information or as a student reading assignment. It is especially effective when read aloud.


Each week on television, police investigators race to the latest crime scene and dazzle viewers by solving the “who done-it” using sophisticated laboratory tests and computer wizardry. While some of the techniques shown are scientific nonsense, occasionally real crime scene investigation techniques, such as “mapping the evidence,” are shown. Brightly colored markers are placed next to evidence or clues, photographed and logged on a scene map. Like following footprints in snow or mud, the sequence of events in a crime sometimes can be deduced from this “map.” 

In the 1980s, when AIDS cases first began to appear, the affliction was thought to be restricted to homosexual men. But as more cases emerged among different populations, the relationship of the disease to the community became unclear. No longer limited only to gay men, HIV was infecting heterosexual men and women, as well as children, of all races and many countries.

The origins of AIDS were very difficult to trace, because most people infected with HIV show no symptoms for many years. During this time, infected individuals can unknowingly pass HIV particles to others through bodily fluids. While many scientists sought to find cures or treatments for AIDS, others sought to determine the origin of the HIV virus. Knowing where it came from and how it spread could help explain how the virus infects people—and how to combat it. Research agencies, including the World Health Organization and the U.S. Centers for Disease Control and Prevention began tracking the prevalence of infection, country by country.

As hoped, mapping HIV/AIDS populations around the world provided important clues. Epidemiologists (scientists who study factors that affect the health of populations) found that countries with the highest incidence rates were among the earliest to report HIV/AIDS infections. Mapping also confirmed that HIV/AIDS had become a pandemic (Greek: pan = “all” + demos = “people”), an infectious disease epidemic that has spread through human populations across continents, or even the entire world.

By tracking back to the earliest reported HIV outbreaks, researchers determined the virus originated in Africa. The first known case of HIV infection was detected in a blood sample collected in 1959 from a man in Kinshasa, Democratic Republic of Congo. However, investigators believe HIV may have existed since the 1930s. And still today, there is an astoundingly high percentage of adults living with HIV/AIDS in central and southern Africa.

It has been established that HIV arose from a related virus found in chimpanzees once common in west-central Africa. A subgroup of chimpanzees still living there was found to have simian immunodeficiency virus (SIV). Researchers confirmed the presence of SIV and its close relationship to HIV by collecting and studying chimpanzee feces from ten forest sites in southern Cameroon. SIV was found in five of the sites. Genetic analysis then enabled scientists to trace the virus to individual chimpanzees.

It is not known exactly how the virus transferred to humans, but cultural evidence indicates that it might have occurred in a single incident. Chimpanzees long have been hunted in Africa as a food source. It is probable that the virus was transferred to a human who was butchering an infected chimpanzee. Perhaps the butcher had an open sore or a cut that provided a pathway for the virus contained in the animal’s blood. Regardless, somewhere in the viral transference process, SIV mutated into HIV, a virus that causes infection and disease in humans. 

From the 1930s to 2009, HIV/AIDS grew from a single case to a global pandemic, with approximately 34 million people now infected by HIV. This number does not include the estimated 30 million people worldwide who have died from AIDS. Due to improved treatments, the infection rate is dropping in some countries. However, these gains are being offset by the rise of infections in other regions, where HIV/AIDS care is minimal. Worldwide, there are approximately 2.7 million new HIV infections (including 53,000 in the U.S.) and about two million HIV-related deaths each year.

Funded by the following grant(s)

Science Education Partnership Award, NIH

Grant Number: 5R25RR018605