ZHANG: South African officials have declared the border with Zimbabwe a disaster area as a result of a cholera epidemic. The U.N. says the death toll is increasing. Here's more. STORY: The cholera outbreak has spread across the busy border as infected Zimbabweans flee their ruined southern African nation, where the health care system has collapsed, leaving cholera victims to fend for themselves. Health officials in South Africa were working hard to control the epidemic which has killed nearly 800 people. South Africa has said it has no plans to quarantine Zimbabweans crossing over to Musina or other border towns. [Dr. Pebetse Maepa, Department of Community Health]: "I am hoping that as long as we are controlling the disease from the other side, like our government has been providing water tanks daily to those people, Water Affairs and Forestry people are busy fixing the sewerage system that side, I am very optimistic, I am hoping that we can eventually deal with this outbreak." More than 15,000 Zimbabweans are believed to be infected with the easily preventable disease, according to the U.N.'s World Health Organization. The outbreak has brought fresh calls for Zimbabwean president Robert Mugabe's resignation.