Prologue
On October 19, 2010, a cholera outbreak was reported in the Artibonite area of Haiti,
10 months after a devastating earthquake had struck the island. Three weeks later
on November 6, 2010, then American Society of Tropical Medicine and Hygiene President
Edward T. Ryan, MD, gave the following Presidential Address at the American Society
of Tropical Medicine and Hygiene Annual Meeting in Atlanta, Georgia.
The American Society of Tropical Medicine and Hygiene traces its origins to 1903,
a time when health professions were organizing to address new health threats, including
those posed by growing international exchanges and evolving colonialism. One of these
threats was cholera, a severe dehydrating illness caused by Vibrio cholerae, but we
meet here 107 years later with our newspapers filled yet again with news of cholera,
this time in Haiti. In October 2010, after a devastating earthquake and displacement
of millions of persons in Haiti, a large and spreading outbreak of cholera began that
shows no signs of abating. We know a great deal about cholera, but as we gather here
tonight, we must acknowledge that we as a species are literally still plagued by it.
What lessons can we as scientists, physicians, and health officers garner from the
story of cholera's impact on humanity, and perhaps more importantly, humanity's responses
to cholera?
I will also preface my Address with the caveat that I am not a historian and that
any errors, omissions, or mis-attributions are my fault. They represent my best knowledge
after spending the last two decades working on cholera, and I welcome revisions and
corrections. As you will see, the story of cholera is both horrifying and rich, with
historical details that are extraordinary.
Cholera is caused by a flagellated gram-negative bacterium, Vibrio cholerae. Two serogroups
of V. cholerae (of approximately 200) are associated with epidemic cholera: V. cholerae
O1 and O139. The pathogen contains two circular chromosomes that have been sequenced,
and much is known about its fundamental microbiology. Vibrio cholerae exists as a
free-living water-based organism, usually in brackish coastal waterways, and often
in association with chitin-shelled organisms and zooplankton. With the right temperature
and nutrient profile, V. cholerae can also exist inland in fresh water, a reality
that underpins many of the more recent cholera outbreaks in Africa and now Haiti.
Historically, the main ecologic niche of V. cholerae was probably the top of the Bay
of Bengal, where salt and fresh water mix in a large delta system fed by the great
eastern rivers of southern Asia.
Although V. cholerae may have existed and caused human disease from antiquity, the
first relatively well-documented written records that describe what was probably a
cholera outbreak date from the 1500s. Gaspar Correia, a Portuguese explorer, described
in the Lendas da India in 1543 an outbreak among army troops in Calicut and Goa to
which 20,000 deaths were ascribed. He noted that the “disease (was characterized)
by vomiting with drought of water accompanying it as if the stomach were parched up
and cramps that force the sinews of the joints, disease sudden-like which struck with
pain in the belly so that a man did not last out 8 hours of time”.
The more modern historical record, however, begins at a time when European colonialism
and economic and military exchanges reached sustained engagement in the upper reaches
of the Bay of Bengal. Since then, medical historians have declared seven global cholera
pandemics. The first pandemic started in 1817 among British troops in what was then
Fort William, Calcutta. The disease spread out across India, down through Southeast
Asia and across to central Asia, and reached as far as Egypt and the shores of the
Caspian Sea before receding. The second pandemic began in 1827, also in the Ganges
delta area, and spread across Asia, up through Europe and across Germany to the port
city of Hamburg. From there it jumped to England and spread throughout the United
Kingdom. It reached France, and was carried by ship to Quebec for its first introduction
to the New World, spreading down the Hudson Valley to New York City and then throughout
the eastern, southern, and western United States. In 1832, the pandemic entered Australia,
and by 1833 had reached Latin America and the Caribbean, probably largely imported
from Spain and Portugal to its colonies. This second pandemic receded by 1837 and
was the first truly modern global pandemic, affecting all inhabited continents. Despite
that, responses to the spread of cholera at this stage were largely local in nature
and not particularly effective.
The third pandemic began in 1839 among British troops in Afghanistan and this pandemic
spread similarly to the second pandemic, receding only by 1855. However, the third
pandemic was associated with a number of major developments. One development concerned
the nature of how humans and health professionals perceived the cause of disease and
illness. At this point in history, a prevailing concept of disease causation in Western
medicine was that of miasma. Miasma (literally from the Greek word for pollution or
defilement) initially ascribed disease to unhealthy smells and emanations from decaying
matter, but miasmaticism grew to incorporate a wider range of root foulness, including
socioeconomic status and moral fiber. A primary tool to fight miasma was hygiene,
a term that echoes down in the name of our Society. The other model of disease origin
at the time, and definitely the minority camp in the 1830s–1850s before the revolutionary
work of Pasteur and Koch and the other great founders of microbiology, was the growing
field of contagiousness. It was on this background that John Snow first encountered,
pondered, and analyzed cholera, and moved the contagiousness concept of disease into
its ascendancy.
Although John Snow is best known now for his work on cholera, during his lifetime
he was mostly renowned as an anesthesiologist; he was the personal anesthetist to
Queen Victoria during delivery of a number of her children. Although these two aspects
might seem unrelated, they are actually intimately linked. Within a year of the description
of the public successful use of ether at the Massachusetts General Hospital in Boston
in October 1846, Snow in England had experimented extensively with ether and published
a seminal work On the Inhalation of Vapour Ether in Surgical Operations, rapidly becoming
a recognized expert in the new field. John Snow's background in gases, ether, chloroform,
their gaseous distribution, and their effects on the human body directly informed
his view of cholera. He reasoned that gaseous emanations from rotting debris and unclean
conditions could not explain the spread of cholera, nor cholera itself, an illness
he had personal experience with having served alone as a medical apprentice in a small
rural English town during the 1831 outbreak.
By 1849, soon after his work on ether, he published his first work on cholera On the
Mode of Communication of Cholera, suggesting water as a transmission source of a causative
(but unseen) agent. This work was not well received at the time (the devastating and
personal reviews in the Lancet make for interesting and sobering reading when seen
in the context of time). During the third pandemic, Snow continued this cholera work,
but focused his response to his critics with data, not conjecture. The core of this
response was what he referred to as his Grand Experiment in which he worked with William
Farr, the chief biostatistician for London and a pioneer biostatistician, analyzing
data from 1848 and 1849 describing cholera-related deaths in London. In this analysis,
Snow compared the cholera death burden among London inhabitants who received their
water from the Southwark and Vauxhall Water Company, which drew its water downstream
of London (after the city's sewage had been added and closer to the Thames River meeting
the open sea [i.e., higher salinity]), to the death rate among persons who received
their water from the Lambeth Waterworks Company, which drew its water upstream of
London. Snow found that the death rate from cholera was 315 deaths/10,000 persons
of London for those who received their water from Southwark and Vauxhall, but only
37 deaths/10,000 persons for those who received their water from the Lambeth Company.
Snow was about to publish his analysis when another large cholera outbreak occurred
in the Soho area of London on the night of August 31, 1854. This outbreak occurred
a few days after a five-month-old baby named Sarah Lewis had died from cholera on
Broad Street. On the night of August 31, hundreds of persons became sick in Soho with
almost 200 deaths within 24 hours, mostly centering on Broad Street. Snow lived close
to Broad Street and personally investigated the distribution of deaths and cases.
He recognized that the largest concentration of cases seemed to associate with use
of the water pump at Broad Street, and he petitioned the St. James Parish Council
to disconnect the handle on the Broad Street pump. Not really believing Snow, but
seeing little downside, the Council agreed. In reality, the outbreak was coming to
an end by the time this action was taken, but it should be noted that Sarah Lewis'
father became sick with cholera on the day that the pump handle was removed, and the
contamination of the water source would have started anew because the draining cesspool
from the Broad Street house of the Lewis family had broken down and was in communication
underground with the Broad Street pump. John Snow's intervention, therefore, probably
prevented a second large outbreak of cholera in Soho.
With his larger Grand Experiment supplemented by the data from the Broad Street outbreak,
Snow republished his work in 1855. This time the data were more convincing, were confirmed
by subsequent enquiries, and more persons began to recognize the importance of Snow's
work. The implications were significant, and facilitated the movement away from considering
cholera as being related to inhalation and gases, to being considered the first recognized
water-borne illness. Quite simply, miasmaticism had been dealt a deadly blow, and
the contagiousness theory of disease took hold. Snow's work is normally considered
the birth of evidence and field-based epidemiology, and pointed the way toward practical
prevention of disease transmission.
Of note, during this third pandemic in 1854, Filippo Pacini, a clinician and scientist
in Florence, Italy, dealing with that city's large outbreak, used microscopy to identify
a curved bacillus in the stool of cholera victims, naming the organism Vibrio cholerae
because it appeared to vibrate under the microscope. Pacini's illustrations leave
little doubt that he had visualized the correct organism. However, his work was largely
ignored.
The fourth pandemic began in 1863 and in a particularly grim chapter of this pandemic,
cholera killed one-third of the 90,000 Mecca pilgrims attending Hajj that year. The
infection then spread through Africa, Europe, Latin America, and the United States
before receding in 1870. This pandemic marked the ascendancy of the contagiousness
theory of disease, and specifically of the water-borne theory relating to cholera.
During this pandemic, policy, public health, and engineering interventions were being
implemented in countries with the resources to prevent cholera deaths.
The fifth pandemic began in 1881 and is referred to as the Steam and Suez pandemic,
spreading from India through Egypt through Africa and Europe, as well as to China
and Japan. During this pandemic, Robert Koch did his pioneering work in Egypt and
then Calcutta in 1883 and 1884, in which he isolated the cholera organism (which he
first called Kommabazillen [comma shaped bacillus]). In recognition of Pacini's precedence,
the organism was subsequently renamed back to Pacini's Vibrio cholerae. Of note, London
averted an outbreak during this pandemic largely through the presence of its new sewer
system that had been completed in 1875 by Joseph Bazalgette. New York similarly averted
an outbreak in 1892 by implementing quarantine in the New York harbor and using the
first laboratory-based public health intervention. Specifically, the U.S. National
Institutes of Health and Centers for Disease Control and Prevention trace their roots
to the predecessor of the U.S. Public Health Service, the Marine Health Service that
was formed in 1798 and originally chartered to provide for the medical care of merchant
seamen.
By the 1880s, Congress had charged the Marine Health Service with examining passengers
arriving with infectious diseases, especially cholera, yellow fever, and tuberculosis.
In 1887, Joseph Kinyoun had set up a one-room laboratory in the Marine Hospital on
Staten Island, New York. He was trained in microbiology and used a new Zeiss microscope
to diagnose cholera cases based on the work of Koch. This development represented
the first laboratory confirmation of cases at a public health level, and enabled targeted
quarantining of ships and prevention of outbreaks. The fifth pandemic, therefore,
showed large advances in microbiology and germ theory with the isolation of the causative
agent, as well as development of diagnostic and public health screening protocols.
It also represented the first division of the haves and the have nots in the global
population. Previous to this time, all persons were equally susceptible to cholera.
Now cholera began to be associated with poverty and global social disparity.
The sixth pandemic was prolonged, and stretched from 1899 to 1923, involving Asia,
Africa and Europe, but sparing the Western Hemisphere. During the Mecca pilgrimage
in 1902, another large outbreak among Hajj pilgrims occurred, and repetitive outbreaks
among Mecca pilgrims resulted in the enforcement of strict quarantines. It was at
the El Tor Quarantine Camp in the Sinai that El Tor V. cholerae, a new biotype, was
first identified in 1905.
In 1961, in what is today modern Sulawesi–Indonesia, the seventh pandemic began with
El Tor V. cholerae re-emerging, and subsequently spanning out in repetitive waves
across the globe. By 1970, cholera had extended into Africa and Europe, and by 1991
was introduced into Latin America. It is sobering to note that in the 1970s cholera
reappeared in Europe after a hiatus of at least 50 years, causing 30 deaths in Naples,
Italy, and more than 2,000 cases in Lisbon, Portugal. Cholera was reintroduced into
Africa in 1970, spreading across the continent. It has taken brutal hold in many areas
of Africa, becoming endemic in many water systems, and now recurrently plagues that
continent. A particularly gruesome outbreak occurred in Goma, Zaire in 1994 in which
50,000 persons died within a 21-day period from a concomitant cholera and shigellosis
outbreak.
Cholera has played major roles in many advances of modern science and public health,
perhaps noting more firsts than any other pathogen (Table 1). For instance, I have
already mentioned that V. cholerae was the first causative agent that was identified
by microscopy. Cholera also led to the first use of intravenous fluid to treat an
ill human. In 1830, Jaehnichen injected six ounces of water intravenously into a cholera
patient; the patient improved but then died two hours later. Also in 1830, the German
surgeon J. F. Dieffenbach injected whole blood into three cholera patients and once
again, although improvement was noted, they died shortly thereafter. During 1831–1832,
a prescient W.B. O'Shaughnessy noted that the purpose of treatment should be “to restore
specific gravity of blood and replace deficient saline matter” in the blood of cholera
patients, prompting Thomas Latta in Scotland to use intravenous fluid replacement
therapy with water and salt. Of note, 5 of 15 patients who were in the end stage of
disease survived, a report that was sufficient to be published in 1832.
Despite this relative success, intravenous fluid therapy was largely ignored until
1908 and 1909 when Leonard Rogers in Calcutta established sterility and protocol techniques,
and showed that sufficient volume replacement with intravenous fluid could reduce
mortality rates from 70% to 30%. Intravenous fluid, therefore, became standard treatment
at this point. In 1910, Andrew Sellards described acidosis in cholera patients, suggesting
that the use of alkali might be of benefit. Once Rogers added alkali to his regimen,
mortality rates decreased further from 30% to 20%. During 1958–1964, Phillips, Watten,
Carpenter, Gordon, and others measured the exact loss of water and electrolytes in
cholera patients, prompting the development of specific intravenous fluid with isotonic
saline and alkali. These researchers found that administering this fluid plus oral
water could reduce the cholera case-fatality rate to < 1%.
During 1902–1963, physiologists had been examining sodium and glucose transport and
their interaction in the intestine, prompting Robert A. Phillips, a U.S. military
physician, to question whether the sodium-glucose water–coupled system may be intact
during cholera. In 1962, he initiated a trial in the Philippines in which patients
received oral solution with glucose that was added for its nutritional value. The
addition of glucose led to water absorption and positive fluid and sodium balance,
but unfortunately, 5 of 30 patients died, possibly from hypernatremia because the
sodium concentration in the solution was high. Because deaths occurred, the protocol
was deemed as less efficient than intravenous fluid treatment and was not pursued
as practical. Pierce in Calcutta and Hirschhorn in Dhaka continued to use isotonic
oral hydration with glucose and sodium in equal concentrations, noting that it decreased
the use of intravenous fluid. Nalin, Cash, and others also recognized that oral cholera
treatment needed to be tailored to the individual amount of dehydration and ongoing
losses, work that was facilitated by the use of a cholera cot (first invented by Watten
in Bangkok in 1959) in which fluids passed by an afflicted patient channel down a
central hole in a rubber cot into a bucket, facilitating measurement of fluid losses
and estimation of required replacement therapy. These investigator and colleagues
in Dhaka noted that using the new protocol of oral fluid replacement decreased intravenous
fluid need by 80% in severely dehydrated adult cholera patients, a result that was
published in the Lancet in 1968.
In 1971 during the Bangladesh War of Independence, there was large displacement of
refugees, and cholera broke out in refugee camps and showed a case-fatality rate of
30%. With limited resources and scant access to intravenous fluids and supplies, health
providers used oral rehydration solution (ORS), demonstrating a shockingly low mortality
rate of 3% under such adverse conditions. This prompted BRAC, a Bangladesh non-government
organization, and the Bangladeshi Ministry of Health through its Oral Rehydration
Treatment Program, to expand the use of ORS, teaching rural families how to make and
use simple home-based ORS. This roll out was facilitated by the work of researchers
and clinicians at the International Centre for Diarrhoeal Disease Research in Bangladesh
(ICDDR,B), who played critical roles in developing quality control mechanisms for
home-based ORS, and conducting clinical trials. It is estimated that ORS has directly
saved 40 million lives since its introduction.
Cholera, therefore, has driven many milestones by evidence-based approaches. Cholera
was a plague; it was the pandemic that defined much of 19th century life, and it was
associated with the global economy and emerging urbanization, presaging influenza
and polio. It also played large roles in the field of public health, including being
the illness upon which epidemiology was founded, detailed transmission was documented,
steps to interrupt transmission were implemented, and cases could be diagnosed. It
also played a major role in the development of public health policies and public health
organizations, and the development of sanitary procedures and techniques. For instance,
in 1851 in Paris, the International Sanitary Conferences began with cholera being
the main focus. These meetings eventually led by 1907 to the first international health
organization, the Office of International Hygiene, which was also based in Paris and
was replaced by the Health Organization of the League of Nations, and eventually by
the World Health Organization (WHO). It was also a cholera outbreak in Egypt that
prompted the first meeting of the World Health Assembly in 1948.
A number of cholera specific issues remain. It is disconcerting that ORS use is not
optimal and decreasing in many locations, pointing out that increased education and
communication at the household level are required. It is also disconcerting that cholera
cots are not more widely used. The ongoing outbreaks of cholera among the most impoverished
persons in the world also highlight some of our failures as a global society. Although
the long-term solution to prevent cholera is safe water and improved sanitation, WHO
currently estimates that 800 million persons globally lack safe water and 2.6 billion
persons lack adequate sanitation. It will therefore be decades, if not longer, before
these injustices are rectified, and as such, the use of cholera vaccines in disease
control and prevention, especially in the 50 countries in which cholera is endemic,
needs to be promoted and evaluated.
So what are the lessons for cholera for us here tonight? First, the cholera wars include
fascinating stories of scientific and evidence-based investigation in basic science,
physiology, toxicology, microbiology, environmental sciences, immunology, vaccinology,
clinical field trials, epidemiology, health delivery, evaluation, and public health
and policy responses. Perhaps the most important lesson in cholera and what I term
the eyes on the prize is the development of ORS. Oral rehydration solution is based
on science, costs a few pennies, can be made and used by the illiterate, and has saved
millions of lives. It requires no special interventions and is as simple as drinking.
It is the most practical, cost-effective health intervention driven by basic science
yet developed, and it represents the paradigm of the interface of basic science, clinical
medicine, and public health.
However, we should take a step back and look at additional lessons from the cholera
story. The first lesson is that basic life scientists need to interface with applied
science and not operate in a disconnected vacuum, however pure and beautiful that
sphere may be. It was applied/translational scientists who took 80 years of wondrous
basic science advancements and developed a rational evidence-based intervention that
has saved millions of lives. In turn, applied scientists and clinicians need to recognize
that they practice in a paradigmatic system and although they can use such systems
as constructs to approach patients, they need to enable evidence to dictate their
responses. This practice will require fluency with advances in basic science and the
ability to question current practice, constantly looking for ways to improve. Public
health officials need to reject settling for current policies just because they are
good enough. Why are oral cholera vaccines not being more widely used and improved
cholera vaccines not being more aggressively pursued? Public health officials will
be required to use practical judicious balancing (but accelerated balancing) of what
is working versus what would be better.
We as a Society also can garner a number of lessons. Tropical medicine was forged
in an earlier wave of globalization, one that grew in part out of imperialism, colonialism,
and military intervention. Our diseases always reflect our reality, and cholera is
no exception; it was the first global pandemic that was able to capture this new ecologic
niche. We are now in a different stage of globalization, one of economic interchange
and rapidity of travel on a backdrop of urbanization and mega-cities. Although tropical
diseases still affect a large portion of the globe, the traditional tropical diseases
now largely affect persons who are being left behind by globalization. We need to
continue to serve these persons, but we also need to recognize that they and we are
facing new challenges. These challenges include emerging infectious diseases, largely
viral and zoonotic in nature, often transmitted by the respiratory route or by vectors.
We need to not only address these, but also recognize that severe weather and climate
change may change the rules of engagement relating to these emerging infections (and
other health issues), and that we need to be flexible and innovative in our responses.
At present, we as a Society are making major contributions in vector biology and arbovirology,
but we are not addressing the large global burden of respiratory infections, which
currently kill more children than any other category of disease. A second challenge
is diseases related to delivery and infrastructure systems. In 2008, the global human
population, for the first time in history, largely resided in cities, often in informal
settlement areas in resource-limited settings. The lack of adequate infrastructure
in many of these settlements means that our current infrastructure systems can actually
worsen many health situations and act as efficient vehicles for disease transmission.
This finding is especially true for food-borne and water-borne diseases, and we as
a Society need to continue to address these important aspects that lead to intestinal
infections that are the second leading killer of children globally. The third general
area concerns the non-communicable diseases that are increasingly afflicting the human
population, including those associated with the use of tobacco and obesity, as well
as diabetes, hypertension, and cardiovascular and oncologic conditions. As a Society,
we do not do a good job in addressing these new global pandemics. How will we respond
to our globalization health threats? Our strength has historically been in generating
scientific knowledge on communicable diseases, and this knowledge has been used to
support informed and evidence-based decision making for more than a century. A question
for us tonight, however, 107 years into the history of our impressive Society, is
will we build upon this base. A century from now, will it be said that we as a Society
also responded to our global health threats, both ancient and new?
In closing, I would like to say what an honor it has been serving you as President
this past year, and God willing, I look forward to working with you going forward.
Epilogue
From its onset in 2010 until 2013, the cholera outbreak in Haiti has thus far affected
more than 600,000 persons, resulting in more than 8,000 deaths. New cholera cases
occur daily. The Haitian outbreak is now the largest in recorded history. Since the
outbreak, a more affordable oral killed cholera vaccine has received WHO pre-qualification,
and studies are evaluating its use in Haiti and elsewhere, although no large-scale
use has yet occurred. The WHO has also formed a cholera vaccine stockpile for possible
use in future outbreaks. The quest for the best long-term solutions of safe water
and adequate sanitation for the people of Haiti and other resource-limited areas continues,
with substantial actions having been taken by national governments, international
agencies, and their partners since 2010. Much has been accomplished in the last 36
months; much remains to be done. As we move forward locally and globally, we will
all need to keep our eyes on the prize.