But evidence mounts that xenotransplantation should be banned outright. Instances of human infection and death from animal viruses that are harmless to their animal hosts are on the rise. In December 1997, a laboratory worker at the Yerkes Regional Primate Research Center in Atlanta died after she was splashed with body fluids from a rhesus monkey infected with the deadly herpes B virus. The pathogenic potential of simian foamy viruses, already found in the bloodstream of several laboratory workers in the US, may only become known after they become well established in the human population. Some scientists theorize that the worldwide spread of HIV infection was caused by a virus that jumped from monkeys to humans.
Pigs are no less of a concern.
There are already 25 known diseases that can be acquired from pigs, including leptospirosis and influenza. Ann Tibell, a researcher at the Karolinska Institute in Sweden, who is using pig cells in experimental diabetes treatments, has detected swine flu antibodies in ten patients, and porcine parcovirus in five. British virologist Robin Weiss theorizes that the use of genetically modified pigs as organ donors may increase the transfer of dangerous viruses to humans. Experts admit that surveillance systems to guard against new and emerging infectious diseases are inadequate. It is doubtful that FDA could adequately monitor animal tissues transplanted into humans.