Ultimate epidemic
What would happen if bioterrorists released a deadly pathogen that could spread from one person to another? Historic epidemics offer an unsettling look at mass death, microbial-style.

In 1917 and 1918, influenza killed about 20 million around the globe.

Between 1347 and 1352, bubonic plague, or "Black Death," killed 30 to 50 percent of Europeans. (Some scientists think a virus similar to ebola may have caused black death, rather than the plague bacterium yersinia pestis, which usually gets the blame. Perhaps. But yersinia pestis has been developed as a bioweapon) Half a millennium ago, Spanish conquistadors brought killer epidemics of measles, smallpox, yellow fever, whooping cough, influenza, and later malaria, to the New World. A lack of immunity to European and Asian diseases caused horrendous waves of illness among Native Americans.

Accident + biowar -- mass death
While most epidemics were transmitted accidentally by infected colonists and soldiers, others apparently resulted from a deliberate effort to pacify the natives through biological warfare. English soldiers, for example, reportedly distributed blankets carrying smallpox virus to Shawnee and Delaware Indians in 1763, during the French and Indian Wars (see "Betrayals" in the bibliography).

"Intent is always hard to prove," says Neil Whitehead, associate professor of anthropology at University of Wisconsin-Madison, "because obviously people don't tend to talk about those kinds of strategies. I'm not suggesting that there was a widespread attempt at biological warfare," but they were not totally ignorant about infection, either. The colonists, for example, "knew that bringing the enemy in contact with rotting corpses could cause disease."

The biological assault, combined with colonization and slavery, virtually destroyed native populations, says Whitehead, who made the epidemic his Ph.D. topic. "The headline news is that the typical disease trajectory in that kind of scenario was an immediate and devastating loss of population." In some cases, he adds, "population bottomed out at 10 percent of the original size."

Since infectious disease preferentially kills the young and the old, the epidemics killed chiefs and shamans, wiping out cultural memories, he says.

Today, Whitehead adds, anthropologists use elaborate precautions to avoid accidentally killing the people they study. "When visiting an uncontacted population," he says, "you want be sure you haven't had a recent cold, that your vaccines are in place."

Meet the biowar agents.