[originaltext]The World Health Organization says 57 nations in southern Africa

The World Health Organization says 57 nations in southern Africa and Southeast Asia are facing a serious shortage of health care workers. This crisis is affecting how governments fight diseases and improve health. The W. H. O says more than 4 million additional doctors, nurses and other health workers are urgently needed to improve the situation.
The warning came in a new W. H.O. report released on April 7th--World Health Day. The report says the health cam crisis is most severe in southern Africa. The continent has 11 percent of the world’s population, but only 3 percent of the world’s health care workers. W. H.O. official Timothy Evans says part of the problem is caused by rich nations that offer high-paying jobs to doctors and nurses from poor countries. In addition, Mister Evans says few trained health care professionals are working where they are needed most. These in poor countries usually work in cities instead of farming areas.
The W. H.O. report provides a ten-year plan to deal with the crisis. It calls for national leadership and new policies for health workers. It also urges more international assistance and foreign aid. The report says that nations facing the most serious shortages must increase health care spending and use public money for health care effectively.
What is the passage mainly about?

Why do some health care workers leave those poor countries?