A study published in a British medical publication says sub-Saharan African countries that have invested in training doctors have lost billions of dollars as clinicians leave home to find work in developed nations.

The authors of the research, published in the British Medical Journal, say the nine countries included in the study — Ethiopia, Kenya, Malawi, Nigeria, South Africa, Tanzania, Uganda, Zambia and Zimbabwe — have lost approximately $2 billion in their investment in doctors who have subsequently migrated abroad. South Africa and Zimbabwe have suffered the greatest economic losses.

The publication reports Australia, Britain, Canada and the U.S. have benefited the most from the international recruitment of physicians.

The researchers are calling for the destination countries to invest in training and health systems in the source countries, in accordance with the World Health Organization's Global Code of Practice on the International Recruitment of Health Personnel.

WHO's Global Code of Practice discourages the active recruitment of health personnel from developing countries facing critical shortages of health workers. It also calls on wealthy countries to offer financial help to poorer ones affected by the emigration.

The code is particularly important for sub-Saharan Africa, with its critical shortage of doctors and its high prevalence of diseases, such as HIV/AIDS, tuberculosis and malaria.