The Young Scourge

Human Immunodeficiency Virus

Every week, the Centers for Disease Control and Prevention publish a thin newsletter called
Morbidity and Mortality Weekly Report. The issue that appeared on July 4, 1981, was a typical
assortment of the ordinary and the mysterious. Among the mysteries that week was a report from Los
Angeles, where doctors had noticed an odd coincidence. Between October 1980 and May 1981, five
men were admitted to hospitals around the city with the same rare disease, known as pneumocystis
pneumonia.

Pneumocystis pneumonia is caused by a common fungus called Pneumocystis jiroveci. The spores
of P. jiroveci are so abundant that most people inhale it at some point during their childhood. Their
immune system quickly kills off the fungus and produces antibodies that ward off any future infection.
But in people with weak immune systems, P. jiroveci runs rampant. The lungs fill with fluid and
become badly scarred. Its victims struggle to breathe enough oxygen to stay alive. The five Los
Angeles patients did not fit the typical profile of a pneumocystis pneumonia victim. They were young
men who had been in perfect health before they came down with pneumonia. Commenting on the
report, the editors of Morbidity and Mortality Weekly Report speculated that the puzzling symptoms
of the five men “suggest the possibility of a cellular-immune dysfunction.”

Little did they know that they were publishing the first observations of what would become the
greatest epidemic in modern history. The five Los Angeles men did indeed have a cellular-immune
dysfunction, one that would turn out to be caused by a virus known today as human immunodeficiency
virus (HIV). The virus, researchers would later discover, had been secretly infecting victims for fifty
years. During the 1980s it finally exploded, and since then it has infected sixty million people. It has
killed nearly half of them.

HIV’s death toll is all the more terrifying because it’s actually not all that easy to catch. You can’t
get HIV if an infected person sneezes near you or shakes your hand. HIV has to be spread through
certain bodily fluids, such as blood and semen. Unprotected sex can transmit the virus. Contaminated
blood supplies can infect people through transfusions. Infected mothers can pass HIV to their unborn
children. Many people who take heroin and other drugs have acquired HIV if they’ve shared needles
with infected users.

Once HIV gets into a person’s body, it boldly attacks the immune system itself. It grabs onto certain
kinds of immune cells known as CD4 T cells and fuses their membranes like a pair of colliding soap
bubbles. Like other retroviruses, it inserts its genetic material into the cell’s own genome. Its genes
and proteins manipulate then take over the cell, causing it to make new copies of HIV, which escape
and can infect other cells.

At first, the population of HIV in a person’s body explodes rapidly. Once the immune system
recognizes infected cells it starts to kill them, driving the virus’s population down. To the infected
person, the battle feels like a mild flu. The immune system manages to exterminate most of the HIV,
but a small fraction of the viruses manages to survive by lying low. The CD4 T cells in which they