I just read that AIDS killed 1.7 million people last year.  I had no idea it was still that deadly.

Over the years AIDS has killed more than 39 million people.  Ebola got all the headlines last year and it is a horrific and deadly disease.  But since it first appeared in 1976, Ebola’s death toll is measured in the thousands, not millions.  AIDS has been and continues to be far deadlier.

Both AIDS and Ebola are zoonotic diseases–meaning they were introduced into the human population from another species.  Scientists have determined that the first human to contract AIDS acquired it from a chimpanzee in Cameroon in about 1908, likely a hunter with an open wound who butchered an infected chimp and came into contact with its blood. The disease has since spread around the world.

While AIDS and Ebola are probably the most-feared zoonotic diseases, they are not alone.  Rabies, of course, is transmitted from animals to humans.  But so are food-borne illnesses caused by e-coli and Salmonella.  Influenza can also be transmitted from animals to humans, as the recent swine-flu and avian-flu scares attest.

There is always a risk of a new disease entering human populations from animals.  By concentrating animals in unhealthy and unsanitary conditions, and pumping them full of antibiotics to keep them alive and stimulate growth, factory farming increases that risk.  The risk is made even greater by the overuse of antibiotics, leading to the creation of antibiotic-resistant bacteria.

Factory farming may never produce a disease as deadly as AIDS. But we can’t be sure it won’t.  And it’s a risk we don’t need to take.