humans became spillover hosts as well. The virus then evolved the ability to leap from human to
human. SARS was a very young virus when scientists discovered it, and the speed at which it was
discovered helped make it a relatively small outbreak. Scientists were able to identify and quarantine
people with the disease, and they banned the sale of civets in markets. Although the SARS virus
managed to spread across much of the world, it only caused about eight thousand cases and nine
hundred deaths before it disappeared.
We can expect more viruses to sweep into our species, and they will probably come at an
accelerating pace. Animals in remote parts of the world have harbored exotic viruses for millions of
years, and for all that time humans have had little contact with them. Now humans are moving deep
into these remote territories to harvest timber, dig mines, and establish new farms. And in the process,
they’ve come into contact with new viruses. Nipah virus, for example, causes dangerous inflammation
of the brain in its victims in Southeast Asia. It’s a virus that normally lives in bats, which once lived
far from humans in jungles. Now the bats—and the viruses—have no jungles to live in.
There’s no reason to think that one of these new viruses will wipe out the human race. That may be
the impression that movies like The Andromeda Strain give, but the biology of real viruses suggests
otherwise. Ebola, for example, is a horrific virus that can cause people to bleed from all their
orifices, including their eyes. It can sweep from victim to victim, killing almost all its hosts along the
way. And yet a typical Ebola outbreak only kills a few dozen people before coming to a halt. The
virus is just too good at making people sick, and so it kills its victims faster than it can find new ones.
Once an Ebola outbreak ends, the virus vanishes for years.
Ebola-like viruses may be frightening, but they probably pose less of a danger to our species than
viruses with a lower death rate that can spread to more hosts. The 1918 outbreak of influenza killed
only a tiny fraction of its victims. But because it infected one in three people on Earth, that tiny
fraction added up to an estimated fifty million people. HIV crept slowly and surreptitiously around
the planet before it was first detected. Instead of causing the terrifying symptoms of Ebola, HIV
quietly breaks down the immune system over the course of many years.
We don’t know which virus will create the next great epidemic, in part because we don’t know the
world of viruses very well. GVFI scientists have discovered a number of new viruses in African
monkeys. Their tests on hunters have revealed those viruses in humans as well. Fortunately, these new
viruses cannot yet spread from person to person. But that doesn’t mean that we can simply ignore
them. Just the opposite: these are the viruses we need to block before they get a chance to make the
great leap into our species.