Download viral superhighway

30
The ViralSuperhighway
CeorgeArmelagos
Anthropologists look at human health through the
wide-angled lens of our species'slong evolutionary
history, our biology in a world of microorganisms,and
the remarkable medical achievementsof our culture.
Anthropologists try to seethe "big picture."
epidemiologists-scientists
As recentlyasthe 1970s,
who study the spread of disease-were publicly saying that the ageof infectiousdiseasewas a thing of the
past. At that time, it appearedthat the world's major
killers, including polio, smallpox, and tuberculosis,
were urder control-or at leastthat biomedical science
had developed the methods to get them under control.
But that has not been the case.Recent decadeshave
seen the emergence of a growing list of new infectious
diseases(like HIV/AIDS and SARS) as well as the
resurgence of old diseases (like tuberculosis and
malaria).
This selection,written by a leading biological anthropologist,showshow pathogenicmicroorganisms
evolve along with humans (and other species)in conjunction with major shifts in patterns of human residence, technological development, and travel. The
author identifies three major shifts in the overall pattern of human disease, or "epidemiological transitions," and links them with three major episodes in
human prehistory and history.
The first shift involved the domesti.cationof plants
and animals that made humans change from nomadic
hunting and gathering to sedentary agricultural patterns of residence. The second epidemiological trarsition was associatedwith the improvements in nutrition,
hygiene, and medicine that accompanied the lndustrial
Revolution in the nineteenth century and has been characterized by the decline of infectious diseaseand an increasein chronic diseasein the developedworld. This
second transition has primarily happened in rich countries. The third epidemiological trarrsition, taking place
as we speak,is the result of contemporaiy patterns of
globalizatiory ranging from global warming and other
forms of environmental degradation to new patterns of
slobal havel and corr[nerce.
Another major contributor to this third shift is the
emergenceof drug-resistant strains of common diseases.As the selectionillustrates, the pathogens that
cause infectious disease,like all other living organisms, are constantly evolving and adapting to new environments. This new development-drug-resistant
strainsof common microbes-is one of the most frightening possibilities humans now face. However, contemporary human societiescan take concretestepsto
counter the threats posed by the "viral superhighway." Taking those steps, however, will require concertedeffort by political leaders,public health experts,
and by all of us.
As you read this selection,ask yourself the follozning
questions:
Armelagos, George. "The Viral Superhighway." This article is
repdnted by permission of the New York Academy of Sciences
from THE SCIENCES[an/Feb 1998):24-29.
202
r
r
How is population health influencedby culture?
l^hat is an "epidemiologicaltransition?"
r
The author describesnot one but three epidemioIosical transitionsover the courseof human history. \,\trhendid each of these transitions occur in
Europe and the United States,and how can each
be explained?
r
How is globalization involved in the increasingly
rapid spreadof infectiousdisease?
r
l^tlat steps can we take to protect ourselves, and
future generations,againstthe dangersposedby
the widening "viral superhighway" ?
Thefollozoing terms discussedin this selectionare
included in the Glossary at the back of thebook:
diseasesofcinilization
gicaI tr ansit ion
epi demiolo
pathogen
THEVIRALSUPERHICHWAY
uponIsraelftom themoming
SotheLod senta pestilence
until theappointedtime;andtherediedof thepeople
ftom
thousandmen
Dan to Beershebasetsentu
-2 Sam.24:15
ing locusts,riversfouledwith
)war-s of crop-destro)
blood, lion-headedhorsesbreathhg fire and sulfur: the
Bible presentsa lurid assortmentof plagues,described
as acts of retribution by a vengeful God. lndeed, realllfe epidemics-such as the influenza outbreakof 1918,
which killed 21 million peoplein a matter of monthscan be so sudden and deadly that it is easy,even for
nonbelievers,to view them asangry messagesfrom the
beyond.
How reassuring it was, thery when the march of
technology began to give people some control over the
scourgesof the past. ln the 1950sthe Salk vaccine, and
later, the Sabin vaccine, dramatically reduced the incidence of polio. And by 1980 a determined effort by
health workers worldwide eradicatedsmallpox,a dise,rsethat had affUctedhumarkind since eail.iesttimes
with blindness, disfigurement, and death, killing nearly
300million people in the twentieth century alone.
But those optimistic yearsin the secondhalf of our
century now seem,with hindsight, io have been an era
of inflated expectations,even arrogance.In 1967 the
surgeongeneralof the United States,William H. Stewart,
announced that victory over infectious diseaseswas
imminent-a victory that would close the book on
modern plagues.Sadly,we now know differently.Not
only have deadly and previously unimagined new illnessessuchasAIDS and Legionnaires'diseaseemerged
in recent years,but historical diseasesthat just a few
decadesago seemedto have been tamed are returning
in virulent, drug-resistarLtvarieties. Tuberculosis,the
ancient lung disease that haunted nineteenth-century
Europe,afflicting, among others,Chopiry Dostoyevski,
and Keats, is aggressivelymutating into strains that
defy the standard medicines; as a result, modern TB
victims must undergo a daily drug regimen so elaborate that health-departm€ntworkers often have to personally monitor patientsto make sure ihey comply [see
"A Plague Retums," by Mark Earnest and John A.
Sbarbaro,September/October19931.Meanwhile, bacteria and viruses in foods from chicken to strawbenies
to alfalfa sprouts are sickening as many as 80 million
Americanseachyear.
And those are only symptoms of a much more
seneral threat. Deaths from hfectious diseasesin the
U.rited States rose 58 percent between 1980 and 1992.
Twenty-nine new diseaseshave been reported in the
past twenty-five years, a few of them so bloodcurdling
and bizarre that descriptions of them bring to mind
tacky horror movies. Ebola virus, for instance,can in
203
just a few days reduce a healthy person to a bag of
teeming flesh spilling blood and organ parts from every
orifice. Creutzfeldt-Jakob disease, which killed the
choreographerGeorgeBalanchinein 1983,eatsaway at
its victims'brains until they resemblewet sponges.
Never slow to fan masshysteria, Holly-wood has capitalized on the phenomenon with films such as Outbreak,ht
which a monkey carrying a deadly new virus from central Africa infects unwitting Califomians arLdstarts an
epidemic that threatensto annihilate the human race.
The reality about infectious disease is less sensational but alarming nonetheless.Gruesome new
pathogens such as Ebola are unlikely to cause a widespread epidemic becausethey sicken and kill so quickly
that victims canbe easilyidentified and isolated;on the
other hand, the seemingly irnocuous practice of overprescribing antibiotics for bad colds could ultimately
lead to untold deaths, as familiar germs evolve to become unteatable. We are living in the twilight of the
antibiotic era: within our lifetimes, scraped knees and
cut fingers may return to the realm of fatal conditions.
Through intemational travel, global col nerce,
and the acceleratingdestruction of ecosystemsworld,
wide, people are inadvertently exposingthemselvesto
a Pandora'sbox of emergingmicrobial threats.And recent rumblings about biological terodsm have highlighted the appalling potential of diseaseorganisms
for being manipulated to vile ends. But although it
may appear that the apocalypsehas arrived, the truth
is that people today are not facing a unique predicament. Emerging diseaseshave long loomed like a
shadow over the human race.
Peopleand pathogenshave a long history together.
Infections have been detectedin the bones of human
ancestorsmore than a million years old, and evidence
from the mummy of the Eg)?tian pharaoh Ramses V
suggests that he may have died from smallpox more
than 3,000years ago. Widespreadoutbreaksof disease
are also well documented. Between 1347 and 1351
roughly a third of the population of medieval Europe
was wiped out by bubonic plague,which is carried by
fleas that live on rodents. In 1793,10 percent of the population of Philadelphia succumbed to yellow fever,
which is spreadby mosquitoes.And in 1875the son of a
Fiji chief came down with measles after a ceremonial
trip to Australia. Within four months more than 20,000
Fijians were dead from the imported disease, which
spreadsthrough the air when its victims cough or sneeze.
According to conventional wisdom in biology,
people and invading microorganismsevolve together:
people gradually become more resistanL and the rnicroorganisms become less virulent. The result is either
mutualism, in which the relation benefitsboth species,or
commensalism,
in which one speciesbenefit:wiihout
204
A ,N D H E A L I N C
CULTURE
R,E L I C I O N
harming the other Chicken pox and measles,once fatal
afflictions, now exist in more benign forms. Logic wotrld
suggest, after all, that the best interests of an orgarism
are not served if it kills its hos! doing so would be like
picking a fight with the person who signsyour paycheck.
But recentlyit has becomeclearto epidemiologists
that the reverseof that cooperativeparadigm of ilJr-ress
can alsobe true: microorganismsand their hostssometimes exhaust their energies devising increasingly
powerful weaporuy and defenses.For example, several variants of human immuno-deficiencyvirus (HIV)
may compete for dominance within a person's body,
placing the immune system under ever-greatersiege.
As long as a virus has al effective mechanism for
jumping from one person to anothet it can afford to
kill its victims fsee"The DeadliestVirus," by Cynthia
Mills, ]anuary/ February 19971.
If the competition were merely a question of size,humanswou ld surelywir: theaveragepersonis l0l7times
the size of the average bacterium. But human beings,
after all, constitute only one species,which must compete with 5,000kinds of viruses and more than 300,000
speciesofbacteria.Moreovet in the twenty yearsit takes
humans to produce a new generation, bacteda car reproduce a half-million times. That disparity enables
pathogens to evolve ever more viru lent adaptations that
quicldy outstrip human responsesto them. The scenario
is govemed by what the English zoologist Richard
Dawkins of the University of Oxford a:rd a colleague
have called the "Red Queen Principle." In Lewis
Carcoll's Throughthe LookingGlzssthe Red Queen tells
Alice she will need to r-ul1faster and faster just to stay in
the sameplace. Staving off illness can be equally elusive.
The Centers for DiseaseControl and Prevention
(CDC) in Atlanta, Georgia,has compiled a list of the
most recent emerging pathogens. They include:
. Campylobacter,
a bacterium widely found in chickof
the commercialpracticeof raising
because
ens
in
cramped,
ulhealthy conditions. It causes
them
million
and eight million casesof
two
between
year
in the United Statesarrd
food poisoning a
between200and 800deaths
. Escherichia
coli 01.57:H7
, a dangerouslymutated
version of an often harmlessbacterium.
Hamburger meat from jack in the Box fast-food
restaurantsthat was contaminatedwith this bug
led to the deathsof at leastfour people in 1993.
. Hantaviruses, a genus of fast-acting, lethal viruses,
often carried by rodents, that kill by causing the
capillariesto leakblood.Anew hantavirusknown
assin nombre(Sparishfor "nameless")surfacedin
1993in the southwestem United States,causing the
sudden and mysterious deaths of thirty-two
peoDle.
. HIV, the deadly virus that causesAIDS (acquired
immunodeficiencysyndrome).Although it was
first obserwedin people as recentlyas 1981,it has
spreadlike wildfire and is now a global scourge,
affectingmore than 30 million people worldwide.
. The strangenew infectiousagentthat causes
bovine spongiform encephalopathy,or mad cow
disease,which recently threw the British meat industry and consumersinto a panic. This bizarre
agent,known as a prion, or "proteinaceousinfectious particle," is also responsiblefor CreutzfeldtJakobdisease,the brain-eaterI mentioned earlier.
A Nobel Prize was awarded to the biochemist
StanleyB. Prusiner of the University of California,
SanFrancisco,for his discoveryof the prion.
. Legionella
pneumophila,
thebacter'rwnthat causes
Legionnaires'disease.The microorganismthrives
in wet environments; when it lodges in airconditioning systemsor the mist machinesin
supermarketproduce sections,it can be expelled
into the air, reaching people's lungs. In 1976thirtyfour participants at an American Legion convention in Philadelphia died-the incident that 1edto
the discovery and naming of the disease.
. Bofteliaburgdorferl,the bacterium that causes
L)..rnedisease.It is carried by ticks that live on
deer and white-footed mice. Left untreated,it can
causecrippling, chronhcproblemsin the nerves,
joilts and ilternal organs.
How ironic, given such a rogues' gallery of nasty
characters,that iust a quarter-centuryago the Egyptian
demographer Abdel R. Omran could obseruethat ir
many modern industrial nations the major killers were
no longer infectious diseases.Death, he noted, now
camenot from outsidebut rather from withir-rthe body,
the result of gradual deterioration. Omral traced the
changeto the middle of the nineteenth century,when
the industrial revolution took hold in the United States
and parts of Europe. Thanks to better nutrition, improved pubJic-healthmeasures,ald medical advances
suchasmassimmunization arLdthe introduction of antibiotics, microorganismswere brought under control.
As people began living longer, their aging bodies succumbed to "diseasesof civilization:" cancer,clogged
arteries, diabetes, obesity, and osteoporosis.Omran
was the first to formally recognlzethat shift in the disease environment. He called it an "epidemiological
transition."
Like other anthropologists of my generatiory I
learned of Omran's theory early in my career, and it
soonbecameabasic tenet-a comforting one,too, implying asit did alr end to the supremacy of microorganisms.
Then, three years ago, I began working with the anthropologist Kathleen C. Bamesof JohnsHopkins University
THEVIRALSUPERHICHWAY
in Baltimore, Maryland, to formulate an expansion of
Omran's ideas.It occurredto us that his epidemiological trarsition had not been a unique event. Throughout
history human populations have r.rndergoneshifts in
their relations with disease-shifts, we noted, that are
always linked to major changesin the way people interact with the environment. Bames and I, along with
JamesLin, a master's student at Johns Hopkins University Schoolof Hygiene and Public Health, have sincedeveloped a new theory: that there have been not one but
tfuee major epidemiological hansitions; that eachone has
been sparked by human activities; and that we are living
through the third one right now.
The first epidemiological transition took place
some 10,000years ago/ when people abandonedtheir
nomadic existenceand began farming. That profoundly
new way of life disrupted ecosystemsand created
denserliving conditionsthat led, asI will soondetait to
new diseases. The second epidemiological transition
was the salutary one Omran singled out in 1921,when
the war againstinfectiousdiseasesseemedto havebeen
won. And in the past two decadesthe emergenceof
illnessessuch ashepatitisC, cat scratchdisease(caused
by the bacterium Bartonellahenselae),
Ebola,and others
on CDC's list has createda third epidemiologicaltrarsitiory a disheartening set of changesthat in many ways
have reversed the effects of the second transition and
coincide with the shift to globalism. Burgeoning population growth and urbanization, widespread environmental degradation, including global warming and
tropical deforestation,and radically improved methods
of transportationhave given rise to new ways of contracting and spreadingdisease.
We are, quite literally, making ourselves sick.
\,\y'henearly human ancestorsmoved {rom African
forests onto the savalna millions of years ago, a few
diseasescame along for the ride. Those "heirloom"
species-thus deslgnated by the Australian parasitologist J.F.A.Sprent becausethey had afflicted earlier
primates-included headandbody lice;parasiticworms
such as pinworms, tapeworms, and liver flukes; and
possiblyherpesvirus and malaria.
For 99.8percentof the five million years of human
existence,hulting and gathering was the primary mode
of subsistence.Our ancestorslived in small groups arrd
relied on wild animals and plants for their survival. In
their foraging rounds, early humans would occasionally have contracted new kinds of illrLessesthrough insect bites or by butchering and eating disease-ridden
animals.Sucheventswould not haveled to widespread
epidemics,however,becausegroups of people were so
sparseand widely dispersed.
About 10,000years ago, at the end of the last ice
age, many groups began to abandon their nomadic
lifestyles for a more efficient and secureway of life. The
2O5
agricultural revolution first appeared in the Middle
East;later, farming centers developed independently in
China and Central America. Permanent villages grew
up, and people tuned their attention to crafts such as
toolmaking and pottery. Thus when people took to
cultivating wheat and barley, they plarLtedthe seedsof
civilization as wel1.
With the new ways, however, came certain costs.
As wild habitats were transformed into urban settings,
the farmerswho broughtin the harvestwith their flintbladed sickles were assailedby grim new ailments.
Among the most corrlmon was scrub typhus, which is
carried by mites that live in tall grasses,and causesa
potentially lethal fever Clearing vegetation to create
arable fields brought farmers frequently into miteinfested terrain.
Irrigation brought further hazards. Standing thighdeep in watery canals,farm workers were prey to the
worms thal causeschistosomiasis.
After tivine within
aquaticsnaiJ:durhg Lheirlarval stage,thoseworms
emerge in a free-swimming form that can penetrate
human skin, lodge in the intestine or urinary trac! and
causebloody urine and other seriousmaladies.Schistosomiasis was well known in ancient Egypt, where outlying fields were irrigated with water frorn the Nile
River; descriptions of its symptoms and remedies are
presewedin contemporarymedicalpap)auses.
The domestication of sheep, goats, and other animals cleared another pathway for microorganisms.
With pigs in their yards and chickens roaming the
streets,
peoplein agriculturalsocieties
wereconstartly
vulnerable to pathogens that could cross interspecies
barriers.Mary suchorganismshad long sincerelched
commensalism with their animal hosts, but thev were
highly dangerousto humans.Milk from inJectei caftle
could transmit tuberculosis, a slow killer that eatsaway
at the lu-ngsand causesits victimsto coughblood ani
pus. Wool and skinswere loadedwith a*hra'., which
can be fatal when inhaled and, in modem times, has
been developedby severalnations as a potential agent
of biological warfare. Blood from infected cattle, injectedinto peopleby biting insectssuchasthe tsetsefly,
spreadsleepingsickness,an often-fataldiseasemarked
by tremors and protracted lethargy.
A secondmajor effect of agriculture was to spur
popuJationgrowth and, perhapsmoreimportant,dinsity.Citieswith populationsashigh as50,000haddeveloped in the Near East by 3000u.c. Scavengerspecies
such as rats, mice, and sparrows, which congregate
wherever large groups of people live, exposed city
dwellers to bubonic plague, typhus, and rabies.And
now that people were crowded together,a new pathogen
could quickly start an epidemic. Larger populations also
enableddiseasessuchasmeasles,mumps, chickenpor;
and smallpox to persist in an endemic form-always
206
A ,N D H E A L I N C
R ,E L I C I O N
CULTURE
present, afflicting Part of the population while sparing
those with acquired immunitY.
Thus the birth of agriculture launched humanity on
a trajectory that has again and again brought people
into contact with new pathogens. Tilling soil and raising livestock 1edto more energy-intensive ways of extricting resources from the earth-to lumbering, coal
mining, oil drilling. New resourcesled to increasingly
complex social organization, and to new and more frequent contacts between various societies. Loggers
today who venture into the rain forest disturb Previ
ously untouched creatures and give them, for the first
time, the chance to attack humans But there is nothing
new about this drama; only the players have char-rged.
Some2,000years ago the introduction of iron tools to
sub-SaharanAfrica led to a slash-and-bum style of agriculture that brought people into contact wltl\ Anopheles
gambiae,anosqtito that transmits malaria.
Improved trarsportation methods also help diseasesextend their reach:microorganismscannottravel
far on their own, but they are expert hitchhikers. \Artren
the Spanish invaded Mexico in the early 1500s,for instance, they brought with them diseasesthat quickly
raged through Tenochtitl6n, the stately, temple-filled
capital of the Aztec Empire. Smallpox,measles,and influenza wiped out millions of Central America's original inhabitants, becoming the invisible weapon in the
Europeanconquest.
L:r the past three decades people and their inventions have drilled, polluted, engineered,paved, planted,
and deforested at soaring rates, changing ihe biosphere
faster than ever before. The combined effects cary without hyperbole, be called a global revolution. After all,
many of them have worldwide repercussions:the
widespread chemicalcontaminationof waterways,the
thinning of the ozone 1ayer,the loss of speciesdiversity.
And such global human actionshave Put Peopleat dsk
for infectiousdiseasesin newly complex and devastating ways. Global warming, for instance, could expose
mlllions of people for the first time to malaria, sleeping
sickness,and other insect-bome illnesses;in the United
States, a slight overall temPerature increase would
allow the mosquitoes that carry dengue fever to survive as far north as New York CitY.
Major changes to the landscape that have become
possible in the past quarter-century have also triggered
After the constructionof the Aswan Dam
new diseases.
rn 1970, tor instance, Rift Valley fever idected 200,000
people in Eg1pt, killing 600. The disease had been
known to affect livestock, but it was not a maior problem in people until the vast quantities of dammed
water becamea breeding grould Ior mosquitoes The
insects bit both cattie and humans, helping the virus
jump the interspeciesbarrier.
kr the eastem United States, suburbanization, another relatively recent phenomenory is a dominant factor in the emergenceof L)..rnedisease-10,000 casesof
which are repoded armually. Thanks to modem earthmoving equipment, a soaring economy,and population
pressures, many Americans have built homes in formerly remote, wooded areas.Nourished by lawns and
gardens and unchecked by wolves, which were exterminated by settlerslong ago, the deer population has
exploded, exposing people to the ticks that carry Lyme
disease.
Meanwhile, widespread pollution has made the
oceans a breeding ground for microorganisms. Epidemiologistshave suggestedthat toxic algal bloomsfed by the sewage, fertilizers, and other contaminants
that wash into the oceans-harbor countless viruses
and bacteria. Thrown together into what amounts to a
dirty genetic soup, those pathogens can urtdergo geneswapping and mutations, engendering newly antibioticresistant strains. Nautical tra{fic can carry ocean
pathogens far and wide: a devastating outbreak of
cholera hit Latin America in 1991after a ship from Asia
udoaded its contaminated ballast water into the harbor
of Callao, Peru. Cholera causesdiarrhea so severeits
victims can die in a few days from dehydration; in that
outbreak more than 300,000 people became ill, and
more than 3,000died.
The modem world is becoming-to paraPhrase
words
of the microbiblogist Stephen S. Morse of
the
Columbia University-a viral superhighway. Everyone
is at risk.
Our newly global society is characterized by huge
increasesin populatiory intemational travef and international trade-factors that enable diseasesto spread
much more readily than ever before ftom Person to person and from continent to continent. By 2020the world
population will have surpassed seven billion, and half
those people will be living in urban centers. Beleaguered third-wor1d nations are already hard-pressed to
provide sewers, plurnbing, and other inJaastructure;in
the future, clean water and adequate sarritation could
become increasingly rare. Meanwhile, political upheavals regularly cause millions of people to flee their
homelands and gather in refugee camps,which become
petri dishes for germs.
More than 500 million people cross intemational
borders eachyear on commercial flights. Not only does
that traffic volume dramatically increase the chance a
sick person will infect the inhabitants of a distant area
when she reaches her destination; it also exposes the
sick person'sfellow passengersto the disease,because
of poor air cilculation on planes. Many of those Passengers can, in tum, pass the disease on to others when
thev disembark.
THEVIRALSUPERHICHWAY
The global economy that has arisen in the past two
decades has established a myriad of cornections between far-flung places. Not too long ago bananas and
oranges were rare treats in northem climes, Now you
can walk into your neighborhood market and find food
that has been flown and trucked in from all over the
world: oranges from Israel, apples from New Zealand,
avocados from California. Consumers in affluent nations expect to be able to buy whatever they want
whenever they want it. l trhat people do not generally
realize, however, is that this global network of food
production and delivery provides countless pathways
for pathogens. Raspberries from Guatemala, carrots
from Peru, and coconut milk from Thailand have been
responsible for recent outbreaks of food poisoning in
the United States. And the problem cuts both ways:
contaminated radish seeds and frozen beef from the
United Stateshave ended up in Japan and South Korea.
Finally, the widespread and often indiscrirninate use
of antibiotics has played a key role in spuning disease.
Forty million pounds of antibiotics are manufactured annually in the United States,an eightyfold increasesince
1954.Dangerous miooorganisms have evolved accordingly, often developing antibiotic-resistantstrains.Physicians are now faced with penicillin-resistant gonorrhea,
multiple-drug-resistant tuberculosis, and E. coll variants
such as 0157:H7.And frighteningly, some enterococcus
bacteria have become resistarrt to nll known antibiotics.
Enterococcusinfectionsarerare,but staphylococcusin{ections are not, and rr.any strains of staph bacteria now respond to just oneantibiotic, vancomycin.How long will it
be before run-of-the-mill staph infections-in a boil, for
instance,or in a surgical incision-become r,rntreatable?
Although civilization can expose people to new
pathogens,cultural progressalsohas an obvious countewailing effechit canprovide tools-medicines, sensible
207
city planning, educational campaigns about sexually
transmitted diseases-to fight the encroachments of
disease.Moreover,sincebiology seemsto side with microorganisms any'way, people have little choice but to
depend on protective cultura1 practices to keep pace:
vaccinations, for instance, to confer immunity, combined with practices such as hand-washing by physicians between patient visits, to limit contact between
peopleand pathogens.
A11too oftery thougtu obvious protective measures
such as using only cleanhypodermic needlesor treating
urban drinking water with chlorine are neglected,
whether out of ignorance or a wrongheaded emphasison
the short-term financial costs.Theworldwide disoaritv in
weallh is also to blame:not suprisingly, the advances
made during the secondepidemiological transition were
limited largely to the affluent of the industrial world.
Such lapses are now begirming to teach the bitter
lesson that the delicate balance between humans and
invasive microorganisms carr tip the other way again.
Overconfidence*the legacy of the second epidemiological tralsition-has made us especially vulnerable
to emerging ald reemerging diseases. Evolutionary
principles can provide this useful corrective: in spite of
al1 our medical and technological hubris, there is no
quick fix. If human beings are to overcome the current
crisis, it will be through sensible changes in behavior,
such as increased condom use and improved sanitation, combined with a coiunitment to stop disturbing
the ecological balance of the planet.
The Bible, in short was not far {rom wrong: We
do bring plagues upon ourselves-not by sinning, but
by refusing to heed our own alarms, our own best
judgment. The price of peace-or at least peaceful
coexistence-with the microorganisms on this planet is
eternalviqilance.