Francesca Tomasi received her B.A. from the University of Chicago and now does tuberculosis research.
Vibrio cholerae is a comma-shaped bacterium that vaguely resembles a pipe cleaner. Far from innocuous, though, it is the etiologic agent of cholera, a serious illness that causes severe dehydration through horrible vomiting and diarrhea. Untreated, it can cause death from excessive loss of fluids. V. cholerae causes disease in humans by secreting what is known as the cholera toxin into host intestinal cells upon ingestion. This toxin causes the opening of cellular ion channels, which usually act as gates to control the influx and efflux of different substances. The result of this forced opening is a surge of watery diarrhea.
Even though the infectious dose of cholera is relatively low, in regions with poor sanitation, untreated food or water, and poor sewerage the pathogen typically remains endemic without rigorous preventive public health measures. Cholera is therefore able to spread to individuals from the environment through contaminated food and water. It also spreads between people via fecal-oral spread, which is exacerbated in areas with poor sanitation and in households, where people frequently come into contact with each other’s bodily fluids.
Additional interactions between V. cholerae and the environment facilitate its ability to infect people, spread, and persist in human populations. The bacterium’s natural reservoir are chitinous organisms (such as planktons) in the water. Studies have shown that vibrios go so far as to biochemically interact with chitin, a relationship that promotes their proliferation and ultimately helps them persist in a dynamic aquatic environment. As a result, V. cholerae can thrive in a marine ecosystem as well as within human hosts. When individuals go to a contaminated river and ingest the water they use to bathe, cook, and drink, they may consume the dose necessary to wreak havoc on their gastrointestinal system. Furthermore, the proportion of asymptomatic to symptomatic cases is quite high with cholera: about 80 or 90 percent of infected individuals who have it do not actually get sick, whereas the other 10-20 percent become quite ill. Regardless, infected individuals of either camp shed the bacteria for months to years and can therefore unknowingly spread the disease to others, contributing to the pathogen’s endemic state in a region.
Cholera is essentially eradicated in developed nations with solid public health infrastructure: well-designed sewerage that prevents the leaking of potentially infected fecal remnants around the environment, and treated or filtered water. In other parts of the world, however, the environmental persistence of V. cholerae is a recipe for disaster.
In 2010, a devastating earthquake struck Haiti, prompting massive relief efforts from around the world. Unfortunately, however, help for a large-scale natural disaster brought harm in the form of an equally dangerous, yet microscopic killer: a cholera outbreak soon hit, killing over 770,000 Haitians, nearly 8 percent of the country’s population. This outbreak, still causing flare-ups today, is the largest cholera epidemic in modern history.
Prior to this epidemic, during the nineteenth and twentieth centuries the world saw six major cholera pandemics, none of which made their way to Haiti. The turn of the twenty-first century saw pandemic number seven, an outbreak caused by a strain of V. cholerae known as El Tor, for its initial identification in a quarantine camp in El-Tor, Egypt. This strain first emerged in Indonesia in the early 1960s and rapidly made its way throughout Asia and the Middle East where it became endemic in places like Nepal by the early 2000s.
The origin of the Haitian cholera outbreak was heavily disputed for months. One camp argued that the earthquake perturbed Haiti’s natural environment and could thus easily have brought a lurking germ out of hiding. After all, environmental disruptions have frequently been attributed to infectious disease outbreaks all over the world. Meanwhile, other parties argued that humans introduced cholera to Haiti when they arrived in the country for relief work.
The answer came when researchers sequenced bacterial samples from patients in Haiti and found they most closely resembled the Asian El Tor strain. Public health experts quickly turned to Nepalese peace keepers, since Nepal is endemic for cholera, and found major inconsistencies in their sanitation practices, including a faulty sewage pipe that leaked into Haiti’s Artibonite River, the suspected source of the outbreak. In May of 2011, the UN released an official report that concluded: “[the] 2010 Haiti cholera outbreak was caused by bacteria introduced into Haiti as a result of human activity…with a pathogenic strain of the current South Asian type Vibrio cholerae.” By then, over 300,000 Haitians had been infected and an estimated 4,500 killed.
Interestingly, however, it was another five years before the UN publicly admitted its foundational role in the outbreak, and only recently did it pledge to compensate affected families. During that half-decade the scourge raged on, while definitive evidence of its source – little bacterial genetic variation within cases, which indicated a single introduction of the bacteria to Haiti; the strain’s remarkable resemblance to the South Asian El Tor strain, which indicated its etiology; and the sub-par sanitation measures taken by peace keepers from a South Asian cholera-endemic country, which told the disease’s epidemiological story – was dismissed as inconclusive speculation.
Today, despite the broadcasted and official conclusions on the origin of Haiti’s cholera epidemic, the UN maintains that it is immune to legal repercussions. Citing international treaties as sources for impunity, the organization has faced multiple appeals courts and humanitarian group efforts demanding financial, infrastructural, and emotional compensation to its victims.
Needless to say, tensions have been high between the United Nations – an organization created to foster international cooperation and peace – and the people of Haiti. To add fuel to the fire, last month Hurricane Matthew struck Haiti with a vengeance, killing hundreds of individuals and displacing orders of magnitude more. What’s worse is that the physical harm inflicted by the storm may pale in comparison to the long-term health effects of once again leaving over a million Haitians without clean water. NBC reports first-hand accounts that Hurricane Matthew’s damage surpasses that of the 2010 earthquake. The New York Times paints an eerie picture of deserted towns, where the inhabitants who didn’t manage to escape the hurricane died during the storm or from a gruesome bout of cholera.
Hurricane Matthew pooled together the key ingredients to sustain a cholera epidemic: infected bodies – of water and of people. Representatives from many aid groups have described surges of cholera cases just days after the devastating storm, citing the added challenges of there being even fewer health officials left to care for the sick. This time around, the WHO sent a million doses of cholera vaccine to Haiti within a few days of the hurricane, but only time will tell the true scope of the epidemic.
To many, it may come as a surprise that a vaccine exists against cholera, but it has actually claimed a spot on the WHO’s list of essential immunizations. So why has it taken so long for organizations to ship cholera vaccines over to Haiti? Cholera is an easily preventable disease given proper resources, and administering a vaccine is like putting a Band-Aid on a wound that needs stitches. Preventive steps mainly include food safety measures and community awareness of protective measures (such as filtering water through a sash or boiling it before use). Nonetheless, some regions like Haiti are so impoverished – and again, in Haiti’s case, in such disorder from a devastating natural disaster – that basic precautionary behaviors are not as sustainable as they are in more resource-rich nations.
As a result, the WHO is currently evaluating the use of vaccines with the goal of ultimately complementing them with the more traditional preventive efforts. Oral cholera vaccines have been shown to be safe and reasonably effective: in general, they confer immunity in 52% of cases the first year post-vaccination and in 62% of cases the second year. While this level of protection is considered only moderate, herd immunity – protection of a population resulting from individual immunization of a large proportion of the community over time – may multiply the vaccine’s overall effectiveness. Nevertheless, more research needs to be done to understand the full effects of mass vaccination in high-risk populations. After all, administering a vaccine on a large scale bears many logistical challenges: cost, timing of doses, production capacity of the vaccine, and prioritization of recipients since vaccine production is never infinite. Some might compare administering a cholera vaccine to large-scale delivery of malarial prophylactic pills in endemic countries: ultimately, it’s more sustainable to get to the root of the problem than to confer short-term protection. For now, of course, a cholera vaccine in the wake of Hurricane Matthew will save thousands of lives.
Cholera has a long, intimate history with the human race. It has made its ravaging way through countless societies around the globe, and crept deeper into the hearts and minds of people through art and literature. Because of this history, we know how to prevent cholera and how to treat it. After all, proper care of a cholera patient – rehydration and electrolytes – virtually wipes away the risk of death. The simple act of running river water through a folded scarf filters out chitinous organisms harboring dangerous bacteria. We also know how to help victims of natural disasters. Simply put, the humanitarian crisis in Haiti is a simple one to mitigate if every capable nation would lend a helping hand.