Atlanta , Georgia ( CNN ) -- The cholera epidemic already blamed for more than 1,100 deaths in Haiti could worsen because of poor sanitation in the earthquake-ravaged country , U.S. medical researchers reported Thursday . A lack of treated drinking water , coupled with poor hand hygiene and food-preparation practices , make the 1.3 million people still living in camps particularly vulnerable , according to a new study published by the U.S. Centers for Disease Control and Prevention . `` The course of the cholera outbreak in Haiti is difficult to predict , '' the report states . `` The Haitian population has no pre-existing immunity to cholera , and environmental conditions in Haiti are favorable for its continued spread . '' Jordan Tappero , a CDC epidemiologist in Haiti , said Haitian authorities and aid agencies are working to limit the epidemic by emphasizing clean water and sanitation . But he added , `` We expect we will be working very hard for many months to come . '' Haiti has not reported a cholera outbreak in more than a century . The current epidemic was first reported in October and has now spread to eight of the Caribbean nation 's 10 provinces , the CDC found . Reports linking the outbreak to Nepalese troops from the U.N. peacekeeping mission MINUSTAH sparked riots in the northern port city of Cap-Haitien on Tuesday . A new round of violent protests erupted Thursday in the capital Port-au-Prince , eyewitnesses told CNN . U.N. officials have denied the Nepalese were to blame for the outbreak . The CDC has said the strain of the cholera bacteria responsible is `` indistinguishable '' from one found in other parts of the world , including south Asia , but researchers are unlikely to be able to pinpoint how it arrived in Haiti . `` The reality is that we have a serious problem here , '' CDC spokeswoman Lola Russell said . The emphasis is on controlling the outbreak , `` so that more people do not become ill and potentially die from cholera . '' The epidemic comes as Haiti -- already the poorest country in the Western Hemisphere -- struggles to recover from the January earthquake that killed more than 200,000 people . Even before the quake , only 12 percent of the Haitian population of 9.8 million received treated tap water and only 17 percent had access to adequate sanitation , the CDC noted . `` The water safety and sanitation systems in Haiti were weak be before the earthquake and made weaker by the earthquake , so conditions are ripe for the further spread of cholera , '' Tappero told CNN . Some symptoms of cholera , an acute , bacterial illness caused by drinking tainted water , can be mild or even nonexistent . But the disease can cause profuse watery diarrhea and vomiting , leading to death by rapid dehydration . The heart of the outbreak is the Haitian province of Artibonite , north of Port-au-Prince . Interviews with victims hospitalized in the first days of the outbreak found that two-thirds of them had been drinking untreated water from rivers or canals , the same percentage did not routinely use chlorine to sanitize drinking water and nearly four out of five defecated in the open . And as the current outbreak spreads , infected people could spread the disease further by preparing food without proper hygiene , the CDC reported . `` The way to prevent acquiring cholera when sanitation is poor is to take your water from a clean water source or treat water yourself in the home , and use good sanitary practices with clean water when preparing and cooking food , '' Tappero said . CNN 's Miriam Falco and Matt Smith contributed to this report .
U.S. report says the cholera outbreak 's course is `` difficult to predict '' Haiti has n't seen a cholera outbreak in more than a century . The epidemic has killed more than 1,100 in the earthquake-ravaged nation .