"As of 21 November 2007, 436 human RVF cases, including 161 deaths have been reported from White Nile, Sennar, and Gazeera states. In addition, 15 cases including 3 deaths were reported in Khartoum state, but they were most likely infected in the other affected areas," the WHO said in a statement.
Sudan's health ministry said on Tuesday that 94 people had died and 362 been infected in the outbreak.
The WHO called on local media, community and religious leaders to ensure people know what measures to take to reduce the risk of infection.
There are no vaccines for humans who contract Rift Valley Fever, usually via mosquitos.
The disease can also be transmitted by eating uncooked meat, drinking unpasteurised milk or being in close proximity to infected animals.
Victims usually experience fever, general weakness, back pain, dizziness, vomiting of blood and extreme weight loss at the onset of the illness.
Many patients recover within a week but others can die, including those with weakened immune systems, experts say.
The fever was first isolated in Kenya's Rift Valley region in 1930s but has since been recorded elsewhere on the continent and overseas.