Question

How did the scientists working on the Vibrio cholerae outbreak in Haiti determine how the bacteria were first brought into the country?

Answer 1

On January 12, 2010, a catastrophic 7.0 magnitude earthquake struck Haiti, affecting 3,500,000 people. In October 2010, nine months after the earthquake, an outbreak of cholera started, which quickly spread all across the country. The strain of cholera sweeping through post-earthquake Haiti originated in South Asia, conclude scientists who did a rapid genetic analysis of bacteria collected from Haitian patients. The finding supports the notion that the cholera bacteria fueling the outbreak arrived on the island via recent visitors.As of January 7, 2014, 8,534 deaths and 697,256 cholera cases have been reported by the Haitian Ministry of Public Health and Population. Many wondered where the cholera in Haiti came from. Two hypotheses as to its origin were presented. The climatic hypothesis argued that nonpathogenic Vibrio cholerae, indigenous in the coastal waters of Haiti, was given the right environmental circumstances and evolved into a pathogenic strain. On the other hand, the human transmission hypothesis suggested that cholera was introduced to Haiti by individuals infected in a foreign country.Waldor, a microbiologist and infectious disease specialist whose laboratory at Brigham and Women's Hospital studies cholera and other pathogenic gut bacteria ,obtained two samples of Vibrio cholerae, the bacterium that causes cholera, from two Harvard Medical School colleagues.A team of scientists there, led by Eric Schadt, sequenced the complete genomes of the cholera bacteria in the samples. The DNA readout showed that the two Haitian strains of V. cholerae isolated from different patients were essentially identical, supporting the idea of a single origin of the nation-wide outbreak. The two strains were also essentially identical to three other Haitian outbreak samples that had been sequenced (but not analyzed) by the Centers for Disease Control and Prevention (CDC). Waldor and colleagues then examined the genes of the Haitian bacteria for clues to the potency of its toxin production and antibiotic resistance.They found that the strain contains a version of the gene that produces cholera toxin and hence, the symptoms of the disease that differs from that found in strains from Latin America at three amino acid locations. Two of these three amino acid changes were present in the now extinct "classical" V. cholerae, a type of V. cholerae that characteristically produces more severe disease. The team concluded from these data that the Haitian strain may be more virulent than the average strain of V. cholerae. That means the strain may cause more severe diarrhea and lead to a higher death rate than usually seen. But examination of the antibiotic resistance genes showed some good news: The strain should be responsive to tetracycline antibiotics. Rehydration is the first-line of therapy, but antibiotics, which are currently being used sparingly in Haiti, can help shorten the length of illness as well as limit the dissemination of the pathogen and so are also an important treatment option.

Cholera, caused by V. cholerae, is a disease characterized by very severe diarrhea and dehydration, which can lead to death in less than 48 hours if left untreated. Cholera is treatable through oral rehydration salt solutions, intravenous fluids, or antibiotics, depending on severity . Ingestion of contaminated water is the main vehicle for human infection.Ingestion of contaminated water is the main vehicle for human infection.There are many serogroups of V. cholerae, but only two – O1 and O139 cause outbreaks. V. cholerae O1 has caused all recent outbreaks. V. cholerae O139 ,first identified in Bangladesh in 1992 caused outbreaks in the past, but recently has only been identified in sporadic cases. It has never been identified outside Asia. There is no difference in the illness caused by the two serogroups.

Cholera transmission in Haiti today is largely a function of eradication efforts including WASH (water, sanitation, and hygiene), education, and oral vaccination, and climate variability.MINUSTAH , The United Nations Stabilization Mission in Haiti ,troops from Nepal were stationed in Haiti starting on October 8, 2010, and set up camp in Meille. Improper disposal of sewage led to the contamination of the Meille tributary, which connects downstream to the Latem River . The first case of cholera occurred on October 12 along the Latem River in Mirebalais , 2 km north of Meille. Water from the Latem River enters the Artibonite River, the major river that spans across Haiti, which flows downstream to St. Marc . The Artibonite River played a significant role in the rapid spread of cholera. During the early onset of the epidemic, reported cases were linked to proximity with the river. A chronological timeline of events involving the Haiti cholera outbreak from July to December 2010.