Remembering his younger brother's choice of water supply that morning,
Yan began mentally mapping the families who had been reported ill,
they all collected water from that communal source.
Yan knew that his next steps would be critical to his brother's survival.
Several cholera treatment centers had been opened in Haiti since the disease
was first introduced into the area likely
by UN peacekeepers who came to Haiti from Nepal.
But the nearest cholera treatment center would have required a two hour trek
including a river crossing and Yan knew that infection with vibrio cholerae
could cause rapid dehydration and death in a matter of 12 hours if left untreated.
In order to result in disease, a relatively large number of
the chomashate vibrio cholerae bacteria need to be ingested
because most of them are killed in the acidic environment of the stomach.
Vibrio cholerae that have recently been shed by another human
are hyper-infectious,
meaning that they're better able to survive passage through the stomach.
Once inside the small intestine, the bacterium uses its flagellum
as a propeller and, guided by chemotaxis, it swims towards
the surface of the intestine and avoids being cleared by peristalsis.
When the bacteria reach the surface, they need to overcome another protective
mechanism, the thick mucous net, that's made by goblet cells, to keep bacteria
away from the surface of the epithelial cells lining the intestinal tract.
Vibrio cholerae makes enzymes that digest the mucous and
allow the bacteria to penetrate the mucous.
Next, the bacteria need to attach to the epithelial cells and
this is mediated by thread like appendages
that grow out of the bacterial surface called pillai, or febriae.
Once the bacterium attaches itself to the cell,
it begins producing a toxin that's engulfed by the epithelial cells.
Inside the cells, the cholera toxin disrupts the functioning of chloride
channels in the cell, allowing large amounts of chloride ion to leave the cell,
followed by large amounts of sodium ion.
Water in the lumen of the small intestine is no longer able to be absorbed and
patients shed liter volumes of stool.
With this stool, the colon loses bicarbonate base and
infected patients become dehydrated and acidotic.
The copious amounts of diarrhea seen in cholera patients
is actually beneficial to the organism that causes the disease.
Vibrio cholerae replicates rapidly inside the small intestine.
And the watery stools allow the newly minted bacteria to exit the host and
be transmitted to another usually via fecal-oral contamination.
This is why in parts of the world where running water and
sanitation aren't available, cholera can spread quickly and easily.
Back at home, Yan sees Filipe deteriorating rapidly.
His eyes are sunken, his skin torque is low and he's too weak to walk.
The young medical student fashions a cholera cot out of a rusted deck chair and
asks his mother to begin sterilizing water by boiling it over the kerosene stove.
When the water has cooled Yan mixes six teaspoons of sugar and
half a teaspoon of salt into one liter of sterile water,
trying to stay calm as he remembers the correct proportions of salt, sugar and
water for a homemade version of oral re-hydration solution, or ORS.