Cholera is an infectious disease caused by the bacterial pathogen Vibrio cholerae. It is often spread in areas with poor sanitation and insufficient separation between sewage and drinking water. Inside the body, it can release cholera toxin, which causes massive watery diarrhea that can lead to severe harm and even death due to dehydration. This also helps to spread it to other hosts via sewage.
It is treated primarily by providing plenty of fluids and salts and, in severe cases, antibiotic treatment. There are preventative measures that can be taken against cholera, including improved sanitation and getting vaccinated.
In early 2010, Haiti was struck by a major earthquake that damaged public sanitation and provided the fertile environment for the explosion of infectious diseases like cholera, that infected about 750 000 people killed around to 10 000 people. This was the most deadly cholera outbreak in recent history. It was also the largest until it was superseded by the 2016-2018 Yemen cholera outbreak that has over 2200 deaths and over 1 million suspected cases as of mid-2018.
But what was the cause of this epidemic? Did the cholera pathogen come from outside the country, or did the rapid environmental change make domestic cholera pathogens more virulent and capable of spreading?
The scientific research that went into is discovering the origin, the cause and the spread of the 2010 cholera outbreak in Haiti was reviewed in a paper entitled The 2010 Cholera Outbreak in Haiti: How Science Solved a Controversy written by Orata, Keim and Boucher and published in the journal PLoS Pathogens in 2014.
The paper is split up into five sections. The first section provides the historical and epidemiological context to the situation in Haiti with the devastating earthquake, the large-scale effects of the epidemic and initial hypotheses developed by researchers. The second section delves into the pathogenesis and genetics of Vibrio cholerae as well as symptoms of the disease and past pandemics.
The third section covers initial research into the issue that suggested a single origin of the outbreak and with the help of traditional epidemiological methods, the human transmission hypothesis was strengthened.
Researchers suggested that the United Nations Stabilization Mission in Haiti (MINUSTAH) troops that had recently been stationed in Nepal had gotten infected there, moved to Haiti, set up a camp near a river that flowed into the largest river in the country but had poor sanitation management.
None of the troops exhibited symptoms of cholera at their medical examination, but they can have gotten infected later or they could have been asymptomatic carriers.
The fourth section deals with even more detailed high-throughput genomic analysis that provided further evidence for the human transmission model. The fifth and final section deals with the promise and perils of sequencing in molecular epidemiology and provides a small update to the legal case filed against the UN for damages.
In 2016, the UN finally accepted responsibility for the Haiti cholera outbreak. They still insist that they are legally immune and do not have to pay reparations and their stumbling efforts to help has been largely weak.