GENEVA (AP) — The situation of 170,000 Sudanese refugees living in camps and settlements across South Sudan's Unity and Upper Nile states is alarming and there are worries about an outbreak of cholera, U.N. refugee agency officials said on Friday.

Heavy rains and flooding in low-lying areas along with cold temperatures have contributed to the spread of respiratory tract infections, diarrhea and malaria, the officials said.

Dr. Paul Spiegel, the chief medical officer for the U.N. refugee agency, said they are considering a mass immunization for cholera, a waterborne disease that can cause acute diarrhea and vomiting and kill within hours through dehydration.

The camps in Upper Nile state are located among the most remote and underdeveloped regions in South Sudan. During most of the year, food is brought in over unpaved roads or flown in on planes and helicopters. Then roads and runways deteriorate when the rainy season starts in June.

In Upper Nile, nearly half the refugees are under the age of 11. The children have been suffering the most because their mothers or other caregivers are too sick and weak to look after them, said U.N. agency spokesman Adrian Edwards.

Edwards says nearly 1,600 children, or nearly 15 percent of all the children younger than five, are severely malnourished in Yusuf Batil, a camp hosting 34,000 Sudanese from Blue Nile state. They are being treated in a special medical program to nurse them to health.

The refugees from the Nuba mountains in Sudan's Blue Nile state have fled fighting between the rebels and Sudanese government forces. Fighting between the government and the rebels broke out in Sudan's South Kordofan state following South Sudan's independence in July 2011.

The number of Sudanese refugees has nearly doubled from 99,000 in April. In camps along the north-south border, they have endured food and water shortages as well as the occasional bombing, which South Sudan says are carried out by Sudanese warplanes.

The refugee agency says it has launched a new drive this month to improve health and sanitation.

"We are putting particular emphasis on good basic hygiene. We are trying to impress upon refugees the importance of fundamentals like hand-washing, collecting water in clean buckets and not defecating in the open," Edwards said.