The odds are stacked against Haiti. Geologically, it's wedged between tectonic plates, where earthquakes happen. Meteorologically, it's in the center of hurricane alley, where massive storms roil. And historically, the country is forever fighting a colonial legacy that left it largely incapable of recovering from natural disasters. Like endemic cholera, caused by the United Nations' botched response to 2010's earthquake and exacerbated by Hurricane Matthew flooding the country's southwestern peninsula.

The hurricane may have put cholera in the news again, but really, the disease never went away. In the six years since cholera seeped from a UN camp's faulty plumbing, it has infected at least 800,000 Haitians and killed nearly 10,000. "There's no doubt that the main route of transmission is contaminated drinking water that hasn't been filtered or heated," says Art Reingold, an epidemiologist at the School of Public Health at UC Berkeley. Its symptoms are diarrhea and dehydration, sometimes serious enough to be fatal. But thanks to the work of Haiti's Ministry of Health, the disease peaked in 2011 at 6,766 cases a week. Since then, the number of cases has dropped by 90 percent, and the fatality rate fell slightly, from 1.04 percent to 0.075 percent.

So that's good news right? But get this: In 2016, the country reported 771 cases every week, with 28,559 in the last ten months. That was before Matthew hit, knocking back the Ministry's progress and bringing the perfect conditions—flooding, mostly— for a cholera epidemic to spread anew. Since the storm, health workers have diagnosed more than 200 people, and 13 have died. "We're seeing a resurgence of an outbreak," says Patrick Dupont, program director for Haiti at the Real Medicine Foundation, a humanitarian support group that works in disaster-stricken areas. "It wasn't completely cured or eliminated in Haiti at all."

Not for lack of trying. Since 2010, Haiti's Ministry of Health has invested in safe water infrastructure, and partnered with NGOs to administer oral vaccines. They established protocols for putting cholera treatment facilities next to, but separate from, general care hospitals. "If a hospital practicing general care identified a cholera patient, he or she was referred to a center, so they could isolated, treated, and doctors could control dissemination," Dupont says.

But those cholera treatment facilities were often just plywood structures or tents. You can imagine how well those survived Hurricane Matthew. Only five of the original 12 remain, according to Sean Casey, the International Medical Corps' emergency response team leader in Haiti. Along with general care facilities, these remaining centers have seen an influx of people since Hurricane Matthew, and healthcare workers are no longer able to isolate cholera-infected patients. When kept in the same area as everyone else, the chance of transmission goes up.

"New outbreaks are happening where cholera treatment facilities can't function the way they're supposed to," says Casey, who flew to Port-au-Prince from the Dominican Republic by helicopter. Now in Le Cayes, the hub of response operations after Hurricane Matthew, he's still trying to understand how bad the outbreak is, because the affected areas are only now becoming accessible. Compared to what the weekly numbers were prior to the storm, the resurgence doesn't seem like much. But the low numbers are probably because the country's health agency and its NGO allies don't have all the data.

Though the direct impacts from the 2010 earthquake claimed more lives than those from Hurricane Matthew, the cholera complications will likely be similar: An outbreak, compounded by bad infrastructure, overworked health services, and extreme poverty.

For now, rescue teams are distributing water purification tablets and working to keep the disease from spreading further. (The World Health Organization is sending a million doses of preventative cholera vaccine). But even if aid workers and local health officials get this outbreak under control again, the odds against Haiti won't have changed.