The toll of people in Iraq infected with cholera has risen to 3,315, the World Health Organization said Wednesday. The number of confirmed infections compares with 2,758 cases reported Sunday by the U.N. health agency. The death toll of 14 has been unchanged in recent days, WHO said. The outbreak first detected Aug. 14 in Kirkuk in northern Iraq has now spread to half of the country's 18 provinces.

"The case-fatality rate has remained low throughout the outbreak indicating that those who have become sick have been able to access adequate treatment on time," WHO said.

Cholera is a gastrointestinal disease that is typically spread by drinking contaminated water and can cause severe diarrhea that, in extreme cases, can lead to fatal dehydration. It can be prevented by treating drinking water with chlorine and improving hygiene conditions.

The global health body estimates that more than 30,000 people have come down with acute watery diarrhea, which may later be confirmed as cholera.

Kirkuk with 2,309 cases and Sulaimaniyah with 870 are the hardest-hit provinces, with numbers still rising. Both are in northern Iraq. But the disease is continuing to spread and it is "highly possible" it will reach as yet unaffected areas, WHO said.

"The numbers of cases are remaining stable in Basra, Baghdad, Dahuk, Mosul and Tikrit," it said. "However, a case has now been confirmed in Wasit, a province that has previously been unaffected by the outbreak."

Diyala, a province neighboring Baghdad, has reported an increasing number of cases of acute watery diarrhea. Although the province has no confirmed cases of cholera, the symptoms indicate the presence of the disease, it said.

The agency said the Iraqi government has taken steps to curb the disease, but that the overall quality of water and sanitation is very poor, which greatly facilitates cholera contamination.

"WHO is in the process of procuring 5 million water-treatment tablets, and two international WHO epidemiologists are being deployed to support the Ministry of Health in Iraq," it said.