Rift Valley Fever has killed nearly 100 people in Sudan since reports of an outbreak surfaced a week ago, the UN World Health Organisation (WHO) says.
Those who work with livestock are most at risk
Gazeera State has seen the most rapid increase in human cases, the WHO says.
In its most serious haemorrhagic form, Rift Valley Fever can kill as many as half of those who contract it.
Herders and livestock workers are most vulnerable as it can be spread through contact with contaminated animal blood or bites from infected mosquitoes.
The WHO says the disease in humans is normally preceded by infection in animals but officials in Sudan have publicly denied that there are any confirmed cases in cattle.
The BBC's Amber Henshaw in Khartoum says it could devastate livestock in Sudan where much of the population relies heavily on cattle farming.
The Food and Agricultural Organization has deployed an animal health expert to Sudan to help the government contain any outbreak in livestock, the WHO said in a statement.
The UN body says it has started holding daily meetings to monitor the spread of the disease.
The incubation period of Rift Valley Fever ranges between two to six days and most patients die after developing haemorrhagic fever.
The WHO says that 96 deaths have been reported from White Nile, Sennar and Gazeera States.
It says the cases in Gazeera are reported in an area close to irrigation canals.