This post initially appeared on Science Blogs

(No pun intended) This just sucks:

As cholera rampages through Haiti, some epidemiologists are warning that the country could face more than half a million cases over the coming year. Yet tracking and treating the disease is proving increasingly difficult as civil unrest grips the county.

As if Haiti hasn't already suffered enough. Vibrio cholerae, the bacterium that causes the disease is transmitted in contaminated water, and can divide rapidly in the digestive tract. The bacterium causes disease by secreting cholera toxin, a group of proteins that hitches a ride into the cell, sneaks itself into the cytoplasm, and then sets to work giving the poor unfortunate host massive diarrhea. The mechanism for this is deviously ingenious. In order for a cell to maintain the proper balance of water and salt in the cell, there are several receptors and pumps that detect subtle changes and turn on and off according to cues in the environment. Cholera toxin upsets this delicate balance by blocking the ability of one of these receptors to turn off, causing affected cells to release loads of ions into the intestine. And where ions go, water follows. The diarrhea seems to be the main point of all this effort - it gets bacteria into the water supply to infect a new round of hosts.

The worst part of an epidemic like this is this disease should be the easiest thing in the world to treat and prevent. People die of dehydration, and the principal method of transmission is contaminated water, so all you need for prevention AND treatment* is clean water. But Haiti's infrastructure was bad before the earthquake, and now there's just no way to get clean water to the thousands of people affected. Death rates for most outbreaks can be kept below 1%, but Haiti had a death rate around 9%. Efforts by aid groups had gotten it down to ~4%, but then:

That gain, however, has been wiped out by riots that were fanned by rumours that Nepalese UN peacekeepers were the source of the outbreak. The row over the source has been self-defeating, says Jon Andrus, deputy director of the Pan American Health Organization (PAHO), the regional office of the World Health Organization. With many of the sick unable to get past roadblocks to reach treatment centres, and deliveries of supplies held up, death rates have again soared past 9%, he says[...]

Last week, PAHO announced that the epidemiology suggested that 200,000 more cases could be expected in Haiti over the next year, but Andrus says that more recent estimates are likely to raise that figure to more than 500,000. We really need to get those oral vaccines online, like yesterday.

*Re-hydration is usually sufficient - if you can keep the patient alive long enough, the infection will usually clear on its own, but sometimes intravenous saline is required since dehydration can occur so quickly.