Figure 1.
Steps in the evolution of the seventh pandemic Vibrio cholerae.
Environmental V. cholerae indigenous in coastal waters can harbor genomic islands (GIs) by horizontal gene transfer, rendering it pathogenic. Pathogenesis of toxigenic (toxin-producing) V. cholerae critically depends on the production of the cholera toxin, which is responsible for the cholera symptoms, and the toxin-coregulated pilus (TCP). The genes for the cholera toxin (ctx) are from the filamentous bacteriophage, CTXφ, that has been incorporated into the genome. The genes in the TCP island encode factors necessary for the colonization of the small intestine in the human host after ingestion of contaminated water. Additionally, seventh pandemic strains are distinguishable from pre-seventh pandemic strains due to the acquisition of additional GIs, the Vibrio seventh pandemic (VSP) islands.
Figure 2.
How the Haiti cholera outbreak started.
(A) MINUSTAH troops from Nepal were stationed in Haiti starting on October 8, 2010, and set up camp in Meille (red circle). Improper disposal of sewage led to the contamination of the Meille tributary, which connects downstream to the Latem River (red arrow). The first case of cholera occurred on October 12 along the Latem River in Mirebalais (orange circle), 2 km north of Meille. Water from the Latem River enters the Artibonite River (orange arrow), the major river that spans across Haiti, which flows downstream to St. Marc (blue arrow). 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. (B) A chronological timeline of events involving the Haiti cholera outbreak from July to December 2010.