The health watchdog has confirmed 306 cases in 10 of Iraq's 18 provinces in 2008, "far below the 4,700 reported last year and even below Iraq's annual average of 600," according to a UN statement.
However, the UN added that cases are building up in rural areas where clean water and sanitation are not freely available. Iraq's cities have been virtually un affected so far, it said.
"WHO also warned against complacency, saying surveillance, accurate reporting and containment initiatives are critical to prevent further spread," the UN statement added.
It said more than two thirds of Iraq's cholera cases were in the central Iraqi province of Babel.
The UN said a mission including WHO and UNICEF officials has reported 12 cholera deaths and a total of 306 cases so far this year. "The mission stressed that this year's outbreak appears less severe than in 2007," the statement said.
Other reports have put the number of fatalities in 2008 as high as 20 while the government last week placed the toll at five people. The health ministry on Thursday said 339 cases have been reported while there is no immediate increase in the number of deaths from the five reported last week.