USIA Washington File - 2 February 1999
Washington -- A team of international scientists have announced
they have traced the origin of the AIDS virus to a closely
related virus in a subspecies of chimpanzee in Africa.
The scientists, who reported their findings January 31 at the
Conference on Retroviruses and Opportunistic Infections being
held in Chicago, said that research will now focus on why the
human immunodeficiency virus (HIV) that causes AIDS is lethal
for humans while the related virus causes apparently no illness
in the chimpanzees, even though humans and chimpanzees are 98
percent genetically similar.
Although scientific researchers have long suspected that HIV-1,
the type of AIDS virus that has caused the overwhelming
majority of cases in the world, came from chimpanzees,
scientists have not been able to identify the precise
subspecies until now. The chimpanzee virus is known as SIVcpz,
or "simian immunodeficiency virus chimpanzee."
"The chimpanzee, which has served as the source of HIV-1, also
quite possibly holds the clues to its successful control," the
head of the research team, Dr. Beatrice Hahn of the University
of Alabama at Birmingham, said in an interview.
Hahn, whose paper will be published in this week's issue of the
journal Nature, said despite the enthusiasm with the discovery,
her team is worried about the fact that the subspecies in which
SIVcpz was found is at "the brink of extinction" in its natural
habitat in west and central Africa. Hahn believes the
chimpanzee's extinction represents a danger to science because
much more needs to be learned about the infection in
chimpanzees in the wild.
Hahn's team has confirmed the origin of the AIDS virus by
analyzing frozen tissue from Marilyn, a chimpanzee who died in
1984 at the age of 26. The researchers have been able to
perform various kinds of genetic analysis that were unavailable
at the time Marilyn died. The chimpanzee subspecies lives in
the African region where AIDS is thought to have started.
HIV presently infects about 35 million people worldwide, with
the first infection probably having occurred 50 years ago,
scientists have reported. Hahn and her colleagues said that
they have conclusive evidence that the HIV virus has spread on
at least three distinct occasions. Hahn believes in the theory
that humans have been infected from chimpanzees in Africa
through exposure to their blood in hunting and when dressing
meat. However, why the epidemic came when it did is not known
Dr. Anthony Fauci, head of the National Institute of Allergy
and Infectious Diseases, said in an interview that his federal
institute would finance substantial research on the simian
virus. He said one focus of the research will be on whether the
different outcomes of infection in humans and chimpanzees
result from small changes in the genetic makeup of the virus or
The latest findings might lead to new tests to discover viruses
in nature that could cause human disease. "No one wants to miss
detecting the next HIV epidemic," said Dr. Harold Jaffe, a
leading AIDS researcher at the Center for Disease Control and
Prevention in Atlanta, Georgia.
Because the chimpanzees are able to live with HIV without
developing the illness, scientists hope their discovery will be
helpful in improving therapies and eventually developing a
vaccine against the AIDS virus.