Illustration by Emma Roulette.
Cholera is nothing new. It’s been one of the great plagues of mankind, with records of its devastation dating back to 700 B.C.E. For centuries, it has remained endemic, or present on a local scale, in the Bay of Bengal, which has been the starting point of seven global pandemics since 1817. Advances in sanitation and public health, however, had kept its large-scale spread at bay since the mid-20th century.
As far back as public health records have been kept, cholera has never had a presence in Haiti. However, events which unfolded in the aftermath of the 2010 earthquake in Haiti have given the bacterial disease a new foothold not only on the island, but potentially the Caribbean as a whole. This resurgence of cholera and the new scope of its spread were discussed at this year’s National Association of Science Writers conference in Gainesville by Dr. Glenn Morris, director of the University of Florida’s Emerging Pathogens Institute.
Pathogens spill over into human populations in one of three ways: a genetically new strain can develop, such as during seasonal flu mutations. The population can become more susceptible, like when our immune systems weaken with age.
But the third way was what brought cholera to Haiti – when established pathogens take advantage of new, emerging opportunities created by human action.
“These [instances] are called anthropogenic,” said Morris. “We do it to ourselves.”
Human action here can be anything from the growing rate of deforestation to the speed and scope of human travel.
Glenn Morris has been director of the Emerging Pathogens Institute since its inception in 2007. And in early November, he gave a lecture at the Science Writers 2013 conference titled “From Haiti to the Hajj – Real-time Science to Prevent Pandemics.”
In the case of cholera’s recent emergence in Haiti and the Caribbean, it was a confluence of human error and environmental catastrophe.
The 7.0 Mw earthquake hit on Jan.12, 2010, destroying over 188,000 homes, killing more than 200,000 people and displacing more than 1,500,000, according to the Disasters Emergency Committee. It destroyed the public health infrastructure – which included water and sewage treatment – along with many of the island’s transport facilities, communication networks, and hospitals.
“It was a setup for epidemic disease,” Morris said. “Specialists in cholera always added, ‘But there hasn’t been cholera in Haiti for 100 years, so it’s probably not going to be cholera.’”
Then came the first diagnoses of cholera. In October of 2010, the Haiti National Public Health Laboratory detected cases in the regions bordering the Artibonite River.
“There was a UN team from Nepal at the epicenter of the outbreak,” Morris said. “The sewage from their camp was not being treated as it was dumped into the river. The treatment facilities had broken down. They were essentially dumping raw sewage into the river.”
Cholera prefers estuarial areas such as the Bay of Bengal and the Ganges River that feeds into it. The bacteria can live for prolonged periods of time in tropical areas. If you ingest enough, some will survive in the stomach, and then take up residence in the large intestine.
Once here, v. cholera turns off the genes it uses to survive in the environment and turns on the ones it uses to produce cholera toxin. This causes severe diarrhea and rapid dehydration by interfering with the intestine’s ability to reabsorb water.
“It becomes hyperinfectious — it has the ability to very rapidly move from person to person–and suddenly you have an epidemic,” Morris said.
Cholera, endemic in Nepal, is also capable of setting up shop in the human small intestine asymptomatically. That is, it can be transmitted in feces without causing any signs of infection in the carrier.
When Morris’ team began examining the surface antigens, or proteins, of sample bacteria found in the rivers, they found that they were identical across the board.
“For those of us who do this type of work… it suggests that you have a single common source,” Morris said.
Morris and his team then used GPS to track the spread of the infection on a case-by-case level. This allowed them to see the spread of the disease in real-time as it travelled down rivers, roads and major highways into the countryside.
The scope of the disease’s spread is now the primary cause for concern. According to the Centers for Disease Control, there were 176 cases of cholera reported south of Mexico City as of Nov.1 – with a potentially unreported outbreak in Cuba.
“We don’t know how big the Cuban epidemic is,” Morris said. “We don’t have data from Cuba, but under-the-table information we’re getting suggests a fairly substantial epidemic.”
He said that some of the cholera strains may have moved in the environment across the strait between Haiti and Cuba.
“It’s been around a long time,” Morris said. “But it’s still very capable of moving rapidly through populations, across continental boundaries, into new countries,” Morris said.
“Pathogens don’t recognize international borders,” he said. “They don’t like showing Visas when they come across.”