Haiti in the Context of the Current Global Cholera Pandemic
Edward T. Ryan
CDC
November 2011
http://wwwnc.cdc.gov/eid/article/17/11/pdfs/11-0849.pdf

Since the early 1800s, there have been 7 cholera
pandemics, and 2011 marks not only the 1-year
anniversary of the reappearance of cholera in Haiti but
also the 50th anniversary of the onset of the current
cholera pandemic that began in Indonesia in 1961. All
previous pandemics lasted 5-25 years before burning out.
However, the current pandemic has shown no evidence of
abating.

Cholera is a disease of impoverishment, displacement,
and unrest, and the 2010-2011 Haiti and global cholera
milestones are integrally related. In addition to Haiti,
during the past 10 years, there have been major cholera
epidemics in Zimbabwe, Kenya, Nigeria, Afghanistan,
Iraq, Somalia, Angola, Guinea-Bissau, Sudan, South
Africa, Malawi, Liberia, and Vietnam. Cholera is endemic
to >50 countries, affects 2-5 million persons each year,
and kills 100,000.

Most of these cases never come to public or media
attention, and many of them occur in areas where cholera
is deeply entrenched and often affects children. In some
areas of southern Asia, most residents will have
serologic evidence of infection with Vibrio cholerae by
their teenage years.

Why has this pandemic persisted for so long? The answer
is that we do not know, but several factors seem to be
major contributors to its longevity. First, the organism
is different from the version microbiologically
associated with previous pandemics. Previous pandemics
for which we have data were caused by the classical V.
cholerae O1 biotype, but the current pandemic is caused
by the El Tor biotype. V. cholerae persists in aquatic
reservoirs, and for unclear reasons, the El Tor biotype
seems to have a distinct transmission or environmental
survival advantage and has replaced the V. cholerae
classical biotype worldwide. This advantage may
translate into increased likelihood that V. cholerae
will become endemic and persist in a local environment
after its introduction into new areas. The El Tor
biotype is also associated with more prolonged clinical
outbreaks, often featuring multiple waves, and has the
ability to cause mild disease or short-term asymptomatic
passage once established in a population. These features
contribute to the silent introduction of cholera into
new areas, as unfortunately occurred this past year in
Haiti.

During the current pandemic, the El Tor biotype has
continued to evolve. In the early 1990s, this biotype
mutated to a new serogroup, O139, and rapidly spread to
several countries in Asia, joining O1 as a cause of
epidemic cholera. Previous immunity to V. cholerae O1
provided no protection against O139. The number of cases
caused by O139 then decreased, leaving the O1 El Tor
biotype as the predominant cause of cholera, perhaps
again underscoring some poorly understood survival or
transmission advantage of this biotype. During the past
2 decades, the organism again evolved and became hybrid,
keeping its El Tor biotype characteristics but
incorporating classical biotype cholera toxin, a feature
that may be contributing to high case-fatality rates
associated with many recent cholera outbreaks. V.
cholerae continues to evolve, and resistance to
antimicrobial drugs is complicating treatment options in
areas with limited resources.

However, changes in the organism only partly explain the
complexity of our current pandemic situation. Cholera is
a disease of the most impoversished, but it is fi rst
and foremost a disease affected by the global economy
and transportation, initially spreading from its
ancestral home in southern Asia along trading and
commerce routes of the nascent global economy of the
early 1800s. Although cholera spreads through global
interactions, it paradoxically predominantly affects
those most estranged from the benefi ts of
globalization. In the long term, economic investment and
civil stability will lead to the demise of cholera, but
with ~1 billion persons currently lacking safe water,
and 2.6 billion currently lacking adequate sanitation,
our current war with cholera will go on for decades.

Do we just grin and bear it, or is it time to change our
response strategy? No one would argue that cholera
response programs need to be based on case detection,
appropriate fl uid management, and provision of safe
water and improved sanitation. However, is it time to
integrate new tools? Previous response plans grew from
previous experience: wild fi re cholera epidemics that
burned out quickly, ability of rehydration strategies to
decrease case-fatality rates to <1%, and a problematic
parenteral cholera vaccine. However, with the propensity
of the El Tor biotype to cause prolonged and recurrent
outbreaks, high likelihood of becoming endemic, ability
to be carried asymptomatically, association with case-
fatality rates of 2%-6% among patients who receive
clinical care during complex emergencies, and
availabilty of improved oral cholera vaccines, is it
time to rethink our plans? Should vaccines be used more
broadly?

Strong evidence would support use of cholera vaccines in
disease-endemic settings, and an evolving body of
evidence, largely from increased interest in cholera
after its appearance in Haiti, suggests that cholera
vaccines might be benefi cial in reactive situations,
i.e., after an outbreak has started. However, such use
would fi rst require additional fi eld and cost-
effectiveness evaluations and intricate planning and
commitment. Would an international stockpile of vaccine
be benefi cial? Who would support and manage it? What
would be the triggers for its use? How would its benefi
t be measured? Similarly, should there be wider or more
specifi c use of antimicrobial drugs in the initial
stages of a cholera outbreak with the goal of blunting
transmission? Would this buy time? Would such
distribution be not only useless, but also detrimental,
accelerating the development of antimicrobial drug
resistance? And why is it so hard to get clean water and
adequate sanitation to those who need it most? What are
the obstacles? How can we improve our track record?

Quite simply, we do not yet know the answers to many of
these questions, but we should not only view the cholera
epidemic in Haiti as a true catastrophe, which it is of
immense proportions, but we should also view it as an
opportunity. Will we use the hydra-headed reappearance
of cholera in Haiti as an impetus to adapt and respond,
learning from our successes and failures, or will we be
illprepared when cholera appears in the next Zimbabwe,
the next Afghanistan, the next Haiti? The next Haiti
will be here sooner than we think.

Dr Ryan is an associate professor at Massachusetts
General Hospital and at Harvard Medical School in
Boston, MA. His research interests are enteric
infections and cholera.

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