Cholera: Haiti’s latest scourge

In Haiti, the body blows just keep coming. About 200,000 died in the January earthquake. Then the recovery was hampered by poverty, an ineffective and corrupt government, and a long tradition of class antagonism and social chaos.

And now Haiti is stricken by a cholera epidemic that has already killed about 1,300.

Cholera is a fast-moving bacterial disease that causes intense diarrhea and can kill within hours. Despite efforts to contain it, Haiti’s epidemic is spreading from its epicenter north of Port au Prince, the capital, and has reached the vast tent cities that still house earthquake survivors.

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In cholera, the Vibrio cholerae bacterium multiplies in the intestines, forcing the patient to release vast quantities of highly infectious watery stool. Lacking proper disposal and treatment, the diarrhea can pollute drinking water and start new infections.

Cholera is vanishingly scarce in the developed world, and cholera thrives on poverty, disorganization and under-development.

Haiti, where cholera had not been seen for a century, has been rocked by controversy about the source of the bacterium. Some angry Haitians blame United Nations peacekeeping troops for bringing it from Nepal, but at this point, treating patients and providing clean drinking water seems more pressing than doing genetic forensics to track the disease to its origin.

From the viewpoint of V. cholerae, chaotic, post-earthquake Haiti may be paradise, but outbreaks have also occurred in Latin America, Africa and India in recent years. The World Health Organization estimates that cholera annually infects three to five million people and kills 100,000 to 120,000.

Prompt treatment with electrolytes dissolved in clean water can prevent death in 99 percent of cases.

A violent announcement

Cholera announces itself with a sudden, violent outbreak of diarrhea – a “rice-water stool” named for its semblance of water used to cook rice. Diarrhea — and sometimes vomiting — can cause massive water loss and electrolyte imbalance. Muscles cramp and eyes recede into the skull.

Falling blood pressure and oxygen starvation cause a state of shock that can kill within minutes. A graphic description of cholera is mortifying: “A mid-nineteenth-century English newspaper report described cholera victims who were ‘one minute warm, palpitating, human organisms-the next a sort of galvanized corpse, with icy breath, stopped pulse, and blood congealed-blue, shriveled up, convulsed.'”

An incubation period as short as two hours is one reason for cholera’s dreadful reputation, but its efficient spread through contaminated water is another. As Haiti demonstrates, the conditions of poverty, filth and social chaos that help spread cholera also hinder prevention and treatment efforts.

At present, health organizations in Haiti are focusing on sanitation, clean water, hand washing, and other tactics to interrupt the chain of infection. Treatment is taking place in dedicated wards.

To restore the body’s electrolyte balance, patients with moderate to severe diarrhea need treatment with an oral rehydration mixture — essentially a medical-grade sports drink containing sodium and glucose dissolved in clean water. Treatment is simple and many patients need no hospitalization if treated promptly.

In severe cases, antibiotics are used to kill V. cholerae, although the main benefit is often a faster return to health and a reduction in the load of bacteria released in the feces.

Very versatile vermin

The cholera bacterium, like any self-respecting microbe, has evolved genetic tricks for optimizing its survival in changing circumstances. Once it passes through the human mouth, V. cholerae:

Transits the highly acidic stomach by entering a shut-down mode Enters the small intestine and builds the protein flagellin, which makes the whip-like flagella that propels the microbe into the gut wall Attaches itself to the small intestine and starts making toxin, a chemical poison that causes the victim to produce copious diarrhea that will transport bacteria to new hosts

Cholera’s big gifts

Like an execution in the morning, fast-spreading cholera has served to concentrate the medical mind. Cholera was first seen for sure in 1817 in India; the disease then traveled with people and their commerce around the world and eventually gave humanity two durable gifts.

The first gift came when a mid-19th-century outbreak of cholera in London spawned the science of epidemiology — the study of epidemics. The story is often told of how, in 1854, physician John Snow marked where cholera cases lived, and realized that they all had gotten water from the same pump.

Even though the germ theory of disease was yet nascent, authorities removed the handle from the pump and the epidemic subsided. Although that removal is credited with ending the epidemic, it may have already been waning.

Snow’s achievement is especially awesome considering that the bacteria that causes cholera would not be identified until 1883, by the great German microbiologist Robert Koch.

By correlating a disease with foul water, Snow showed that epidemics could be understood by analyzing the timing and location of the illnesses — two rudiments of epidemiology. And that led to a second gift: As epidemiologists realized that drinking feces was dangerous, not just disgusting, the health-giving revolution of sanitation got under way.

Virtuous vaccines?

Antibiotics kill cholera bacteria. But carpet-bombing with antibiotics (“mass chemoprophylaxis” in medico-lingo) is inadvisable because it stimulates bacteria to resist the drugs.

Vaccines must be given before an epidemic gets under way, and thus are most suitable in regions where cholera is endemic, like South Asia. But oral cholera vaccines are showing progress:

In a small study in Cuba, a vaccine raised immunity to infection without causing serious side effects A study of infants in Bangladesh showed that adding a zinc supplement greatly boosted immunity A large test of 67,000 people in Kolkata (Calcutta) India, compared cholera vaccine with placebo, and found that cholera was less than one-third as common among people who got the vaccine. The vaccine even worked for kids aged 1 to 5, who are most severely stricken by cholera

Breaking the chain

Infections are contained by interrupting the chain of infection; and no fundamental scientific or social hurdles prevent this from being done with cholera. Unlike HIV, cholera is not spread by sexual contact. Unlike tuberculosis or influenza, it is not spread by coughing.

Instead, cholera prevention requires attention to boring, even repulsive, topics like safe drinking water and sewage treatment. Granted, the technology can be expensive, but water and sanitation are also the primary defense against microbes, viruses and parasites that cause dozens of other waterborne diseases.

The United Nations’s Millennium Development Goals aim to raise the proportion of people getting clean water and adequate sanitation, but Unicef says progress is mixed: “Two and half billion people are still without access to improved sanitation – including 1.2 billion who have no facilities at all and are forced to engage in the hazardous and demeaning practice of open defecation. The news is better for water: the number of people without an improved source has dropped below one billion for the first time in history.”

In 2010, 884 million people have no access to “improved” drinking water, including 330 million in Sub-Saharan Africa, 222 million in Southern Asia and 151 million in Eastern Asia.

India and China account for the lion’s share of progress in both water and sanitation. Globally, city folks usually score higher in these basic barometers of human development.

So do rich people.

In terms of public health, clean water, clean air and sanitation are the big three environmental goals. By themselves, diarrhea diseases cause 4 percent of all time lost to illness, when measured by disability-adjusted life years.

The cholera question is scientifically straightforward, and is quickly solved when resources and social organization are available. Yet even if the victims of cholera are poor and powerless, the benefits of clean water and sanitation are so manifold that it’s hard to accept that these basic requisites for health are not for everybody.

But as the population soars, as people continue flooding into shantytowns around megacities, and as income inequality remains a fact of life, we anticipate this is not the last article you’ll read about such an avoidable epidemic.

– David Tenenbaum



















