sciencemag.org SCIENCE 524 29 APRIL 2016 • VOL 352 ISSUE 6285
Since the beginning of the Industrial Age,
humans have been perturbing the natural
world in ways that bring us closer to the
pathogens that kill us. Often, we are not
their intended host. But we’ll do.
In 1832, when cholera made it to Canada
via steamship, it killed 3000 people in 11
days in Montreal and Quebec City. With
advances in technology, the modes of transport have only become quicker. In 2003,
SARS—a coronavirus that causes an acute
respiratory sickness—passed from horseshoe bats to palm civets in a market where
exotic animals were sold for food in Guang-zhou, China. A few dozen people were
sickened. SARS became a global concern
when an infected doctor checked into the
Metropole Hotel in central Hong Kong and
transmitted the disease to his fellow tenants. Within 24 hours, it was in Singapore,
Vietnam, Canada, Ireland, and the United
States. It eventually made it to 32 countries.
SARS is gone, for now. But cholera is
back, erupting across Haiti after a 2010
earthquake. MRSA now kills more Americans each year than AIDS. The next great
contagion is out there: waiting, hiding,
Sixty percent of newly emerged pathogens originate in animals. Cows gave us
measles; pigs brought pertussis; ducks
In the 1760s, the British made a fateful decision to inhabit the Sundarbans, a wild coastal region in India, near Bangladesh. There, for the first time, humans came into direct contact with copepods, tiny zooplankton that were
infested with a bacterium called Vibrio
cholerae. Before 1760, it had killed no one.
But once in contact with humans, it mutated and became pathogenic and transmissible from one person to another. By 1817,
and for the next 100 years, V. cholerae was
an efficient killer.
The story of cholera, and the death and
destruction it has wrought on humankind,
provides the backdrop for Sonia Shah’s excellent Pandemic: Tracking Contagions,
from Cholera to Ebola and Beyond. Shah
explores the essential factors needed to
ignite a pandemic: from its initial jump to
humans to its global spread, pathogens are
often aided by lack of hygiene, overcrowding, and political corruption.
Shah began thinking about emerging
pathogens when multiple-resistant
Staphylococcus aureus (MRSA) entered her house,
infecting and reinfecting her family for 3
years. Using the cholera pandemics of the
19th century for context, she writes about
the emergence of modern pandemics. They
are legion: West Nile virus, severe acute
respiratory syndrome (SARS), MRSA, Lyme
disease, Ebola, and others. What factors
caused them? How do we contain them?
Which terrifying pathogen comes next? Can
we stop it?
Pandemic is enlightening—and relent-
lessly frightening—on every single page.
With cholera, the bodies turn blue; the
blood thickens. At one point, about half-
way through the book, I noticed an itchy
red blemish on one of my toes and was
convinced I had two or three days left. The
monkeypox, I surmised. And you will, too.
provided influenza. About 70% of new
pathogens come from wild animals. The
suspected host species for the Ebola virus
is a bat. Although primates represent only
0.5% of vertebrates, a fifth of all zoonotic
pathogens come from them—including HIV
During the winter, writes Shah, in urban
areas across the United States, the major-
ity of aerosolized bacteria come from dog
feces. My neighbor, who twirls a heavy-
looking bag of dog feces in the air twice a
day on his walks around the block, is just
one culprit among millions.
We know that the pathogens come from
the wild and that our encroachments in-
fluence their mutability and enable their
spread, but epidemiologists still can’t pre-
dict how or when our perturbations will
cause an outbreak. In 2009, Shah writes,
dengue fever erupted in Florida for the first
time in 70 years. A peak in home foreclo-
sures had left water in abandoned swim-
ming pools across Key West, a haven for
Every time humans disrupt fragile
ecosystems, we stumble farther into the
darkness. Will we eventually encounter a
copepod that harbors a bacterium even
worse than cholera? Or a primate whose
immune system is overrun with a virus we
can’t control? Will gradual climate change
allow fungi the opportunity to evolve the
ability to survive within the relative furnace
of a human body?
Whatever comes, this time a global army
of virologists, epidemiologists, and doctors
will be waiting for it.
By Christopher Kemp
The reviewer is at the Department of Translational Science and
Molecular Medicine, Michigan State University, Grand Rapids,
MI 49503, USA. Email: firstname.lastname@example.org
Lessons learned from past
pandemics offer insight into
how to stop the next one
Tracking Contagions, from
Cholera to Ebola and Beyond
Sarah Crichton Books,
2016. 287 pp.
Vibrio cholerae was inadvertently introduced into a major Haitian water source by United Nations
peacekeepers in the aftermath of the 2010 earthquake, leading to the worst cholera epidemic in recent history.