that outbreak, masked palm civet cats sold in live animal markets
passed the virus to people. It wasn’t clear whether civets were the
initial source of the virus, or if they caught it from some other
animal. Since then, evidence has been building implicating species of
horseshoe bats as the origin (SN: 11/30/13, p. 13). Until now,
though, coronaviruses isolated from bats were genetically distinct
from the one that caused the 2003 outbreak, suggesting that bat
strains weren’t the direct ancestor of SARS.
five years of surveying bats in a cave in southern China’s Yunnan1
Province, Zhengli Shi and colleagues discovered 11 new strains of
SARS-related viruses in horseshoe bats (especially in Rhinolophus
sinicus). Within the strains, the researchers found all the genes to
make a SARS coronavirus similar to the epidemic strain, says Shi, a
virologist at the Wuhan Institute of Virology, Chinese Academy of
new strains are more similar to the human version of SARS than were
previously identified bat viruses, says Matthew Frieman, a virologist
at the University of Maryland in Baltimore.
analyzing the new viruses’ complete genetic makeup, Shi and her
colleagues retraced the steps that might have given rise to the
original SARS virus. A few spots in the viruses’ DNA seem
particularly prone to rearrangement, so remixing happens often. The
study suggests that recombination between viruses has shaped the
evolution of SARS, says Baric.
of the strains could already grow in human cells, Shi’s team found.
That indicates “there’s a chance that the viruses that exist in
these bats could jump to people,” Frieman says. “Whether they
will or not is anybody’s guess.”
to head off that jump by getting rid of the bats is not a solution,
say Frieman and Baric. Bats perform many important ecological tasks,
such as eating insects and pollinating some plants. Coronaviruses
don’t make bats sick, so studying bats’ immune systems, Frieman
says, could give scientists clues about how to fight the illness.
studies of viruses from horseshoe bats (shown) in one cave in China
suggest the animals are reservoirs of SARS coronaviruses. Bats harbor
many viruses that can sometimes infect people, including Ebola and
Marburg. LIBIAO ZHANG/GUANGDONG INSTITUTE OF APPLIED BIOLOGICAL