are, will allow the mutation of Swine Ebola into versions that allow
easy human-human infection.
If Swine Flu Weren't Enough, Now There's Swine Ebola
Scientists report that domestic pigs harbor Reston ebolavirus, the
only Ebola species that has not caused disease in humans
By Brendan Borrell
EBOLA IN PIGS: A cook roasts a baby pig at the Lydia Lechon restaurant
in Quezon City, Philippines
e-mail print comment
Don't worry, it can't hurt you—yet.
Scientists have identified Reston ebolavirus—a member of the deadly
Ebola group of hemorrhagic viruses—in domestic swine from the
The virus, which looks like a piece of yarn with a slight bend, is the
only Ebola pathogen not known to cause disease in humans. Even so, the
U.S. Centers for Disease Control and Prevention in Atlanta considers
it a biosafety level 4 pathogen, reserved for the most dangerous and
Ebola and the closely related Marburg viruses are highly contagious,
causing vomiting, diarrhea and bleeding with death rates as high as 90
percent. These viruses, originally from Africa, are thought to be
caught from close contact with monkeys and apes, their primary hosts,
although they have also been isolated from bats that show no symptoms.
Indeed, Reston ebolavirus was first identified in 1989 in crab-eating
macaque monkeys that were shipped from the Philippines for research in
Reston, Va. Human caretakers developed an immune response to the
virus, but they never came down with any symptoms.
The latest outbreak of the Ebola family was discovered in July 2008 as
the Philippine Department of Agriculture was investigating "blue ear
disease" in pigs, a respiratory condition that causes their ears to
turn blue from lack of oxygen. Investigators sent tissue and blood
samples to Michael McIntosh at the U.S. Department of Agriculture's
Foreign Animal Disease Diagnostic Laboratory at the Plum Island Animal
Disease Center in Greenport, N.Y.
McIntosh says he was surprised to find that the tissue samples also
contained the Reston strain, which had not been previously identified
in swine. His team also confirmed pig-to-human Ebola transmission by
identifying six pig handlers, whose blood tested positive for
antibodies to the virus, although they showed no symptoms. Manila had
announced preliminary findings in January, and McIntosh's study is
published in this week's Science.
McIntosh says there are still a lot of unknowns, including how the
virus was transmitted to the pigs and whether they show any symptoms
independent of blue ear disease. He worries that the virus's passage
through pigs could allow it to mutate into something more harmful.
The research also raises the possibility that pigs could be infected
with lethal Ebola strains. "What is the level of risk? We really don't
know," he says, "The fact that it shows up in domestic pigs raises