Via NPR's Shots health blog: Scientists Find New Wrinkle In How Cholera Got To Haiti. Excerpt:
[Rita] Colwell, an internationally recognized expert on the interaction of cholera and environmental factors, thinks Haiti's explosive epidemic is most likely explained by the "perfect storm" of three converging factors.
"You have this massive earthquake in January 2010," she says. "The geology of Haiti is limestone. With earthquake effects disrupting the rivers, the rivers become very alkaline." Colwell's studies have shown that the bacterium Vibrio cholera thrives in alkaline waters.
"Then Haiti had one of the hottest summers on record," she continues. That warmed the estuaries where cholera likes to breed in tiny crustaceans, further abetting the bacteria's cause.
"That was followed by a hurricane that skirted Haiti, causing heavy rain and flooding," Colwell points out. "With all the river systems churned up with nutrients and warm water, and proper alkalinity, it would be ideal for the organism to become quite dominant."
No doubt some will be skeptical. With Haiti's climate, geography, proneness to hurricane-related flooding and notorious poor sanitation, some may doubt that cholera epidemics could have been absent, or overlooked, until 20 months ago.
But some scientists think Colwell is onto something.
Dr. David Sack of the Johns Hopkins Bloomberg School of Public Health doesn't buy the hypothesis that Nepalese peacekeepers started the epidemic by contaminating a leaky latrine upstream from the first cholera cases.
He thinks the epidemic exploded too soon after the Nepalese reportedly arrived in Haiti. UN officials tell him that was on October 8, and the first cholera case was recorded on October 12 in a town near the UN camp.
"Cholera's incubation period is at least 24 hours, sometimes two or three days," Sack told Shots. "Just to have a cholera vibrio floating downstream, and considering the dilution factor – well, it raises questions in my mind. Not that it wasn't imported. I think it was imported. I just question when it was imported."
Sack thinks we may never know how the South Asian strain of cholera got into Haiti.
As for the non-01/O139 strain, Sack thinks it might have been hiding in Haiti's environment, waiting for Colwell's perfect storm.
I look forward to a good epidemiological debate about this, supported in part by the UN—which has stubbornly declined to take any responsibility for the outbreak.