The United Nations has declared a meningitis outbreak in Sudan’s troubled North Darfur state with 27 suspected cases and 2 deaths, a U.N. official said on Wednesday.

U.N. spokeswoman Radhia Achouri told reporters in Khartoum four cases of bacterial meningitis had been identified in Saraf Omra camp for those who have fled fighting in Darfur. Three were in the same week.

“About 160,000 doses of meningitis trivalent vaccine have been requested from the World Health Organisation in Geneva,” she said.

Sudan’s health minister warned last week he expected an epidemic of meningitis in Sudan and said the government had stockpiled vaccines to deal with it.

Meningitis is an infection of the fluid in the spinal cord and fluid that surrounds the brain. Bacterial meningitis is the more severe form that can result in brain damage and even death.

In crowded camps for refugees, diseases like meningitis can spread uncontrollably.

Achouri also said cases of dysentery were being reported in South Darfur camps surrounding the state capital Nyala. Aid agencies have begun a hygiene campaign to stop the spread of bloody diarrhoea.

Almost 2 million people have fled the fighting during a two-year-old rebellion in Darfur to makeshift camps where thousands die every month from malnutrition or disease.

One of the world’s largest humanitarian operations is in progress in the region the size of France, but continued violence has hindered aid efforts.

Achouri read a statement by the top U.N. official in Sudan, Jan Pronk, condemning the latest violence directed at aid workers in Darfur.

A USAID official was shot in the face on Tuesday when a clearly marked aid convoy was ambushed by armed gunmen. The unnamed worker is stable in hospital.

“There is ground now to assume that foreigners are being directly attacked,” Pronk said according to the statement.

“These incidents are not likely to stop unless a very robust protection force of at least 8,000 troops is deployed in Darfur to protect the civilian population and the humanitarian workers and… deliveries.”

The African Union has about 2,000 troops on the ground in Darfur with a mandate to monitor a shaky ceasefire agreed last April and limited power to protect those displaced in the camps. Pronk says this is not enough.

He added there were no warning shots fired at the convoy as had been the case previously in Darfur.

“The attack was clearly an ambush since there was no indication that warning shots were fired before shooting at the convoy,” he said.

The United Nations recently evacuated 44 U.N. and aid agency staff from parts of West Darfur after militia threats to target foreigners. Achouri said all roads bar one were reopen to U.N. travel in the west and staff had returned to work, but that the threat was still being assessed.