A Zambian healthcare worker performs a malaria test during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership, visits the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (R), Goodwill Ambassador of the Roll Back Malaria Partnership, visits the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

South African singer Yvonne Chaka Chaka, Goodwill Ambassador of the Roll Back Malaria Partnership, visits the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (L) and South African singer Yvonne Chaka Chaka, Goodwill Ambassadors of the Roll Back Malaria Partnership, visits the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (L), Goodwill Ambassador of the Roll Back Malaria Partnership, visits the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (2nd R) waves on a dinghy on the Roll Back Malaria Zambezi Expedition in the Katombore village about 60 km (37 miles) from Livingstone April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian boy sits inside a mosquito net offered by the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian villagers look at a dinghy of the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian woman carries her baby on her back at the paediatric section of the General Hospital in Livingstone April 22, 2008. Zambia will host World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme, on April 24. REUTERS/Thierry Roge (BELGIUM) 

Zambian villagers unload a dinghy of the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian healthcare worker Laite Hanzonde performs a malaria test during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian child lies on his bed at the paediatric section of the General Hospital in Livingstone April 22, 2008. Zambia will host World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme, on April 24. REUTERS/Thierry Roge (ZAMBIA) 

Zambian healthcare worker Laite Hanzonde gives information to villagers during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian healthcare worker checks a malaria test during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian villagers display a mosquito net offered by the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian healthcare worker Laite Hanzonde performs a malaria test during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid boards a dinghy on the Roll Back Malaria Zambezi Expedition in the Katombore village about 60 km (37 miles) from Livingstone April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian woman holds her child at the paediatric section of the General Hospital in Livingstone April 22, 2008. Zambia will host World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme, on April 24. REUTERS/Thierry Roge (BELGIUM) 

Belgium's Princess Astrid (L) talks to South African singer Yvonne Chaka Chaka, a UNICEF goodwill ambassador on Malaria at the Livingstone International Aiport in Zambia, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical expedition teams will travel more than 2,500 km (1,553 miles) on inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medication to remote areas. REUTERS/Mackson Wasamunu (ZAMBIA) 

A Zambian child lies in his bed in the pediatric section of the General Hospital in Livingstone April 22, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme on April 24. REUTERS/Thierry Roge (ZAMBIA) 

Zambian healthcare worker Laite Hanzonde (R) and Roll Back Malaria Zambezi Expedition leader Andy Leeman (L) give mosquito nets to villagers in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian child gestures next to a dinghy boat of the Roll Back Malaria Zambezi Expedition in Katombore village, about 60 km (37 miles) from Livingstone, April 22, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme on April 24. The medical teams of the expedition will travel more than 2,500 km in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian healthcare worker Laite Hanzonde gives information to villagers during the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Zambian villagers display a mosquito net offered by the Roll Back Malaria Zambezi Expedition in Matongo village, about 60 km (37 miles) from Livingstone, April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1,553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

A Zambian woman carries her baby on her back at the paediatric section of the General Hospital in Livingstone April 22, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the World Health Organisation's Roll Back Malaria programme, on April 24. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (2nd L) poses with the members of the Roll Back Malaria Zambezi Expedition, Zimbabwe's Time Kurothwi (L), Switzerland's Andy Leeman (C), Germany's Herge Bendl (2nd R) and New Zeland's Leo Fahey (R) in the Katombore village about 60 km (37 miles) from Livingstone April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid waves on a dinghy on the Roll Back Malaria Zambezi Expedition in the Katombore village about 60 km (37 miles) from Livingstone April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (2nd L) sits on a dinghy on the Roll Back Malaria Zambezi Expedition in the Katombore village about 60 km (37 miles) from Livingstone April 23, 2008. Zambia will host the World Malaria Day in the presence of Belgium's Princess Astrid, Goodwill Ambassador of the Roll Back Malaria Partnership on April 25. The medical teams of the expedition will travel more than 2,500 km (1553 miles) in inflatable boats through Angola, Namibia, Botswana, Zambia, Zimbabwe to deliver mosquito nets and medications to remote areas. REUTERS/Thierry Roge (ZAMBIA) 

(L-R) Belgium's Princess Astrid, Roll Back Malaria Partnership Executive Director Awa Coll-Seck and South Africa's singer Yvonne Chaka Chaka listen to a speech in Katombore village, 60 km from Livingstone, April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (C) and South Africa's singer Yvonne Chaka Chaka (R), Goodwill Ambassadors of the Roll Back Malaria Partnership, visit the paediatric section of the General Hospital in Livingstone April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA) 

Belgium's Princess Astrid (R), Goodwill Ambassador of the Roll Back Malaria Partnership, distributes mosquito nets in Katombore village, 60km from Livingstone, April 24, 2008, ahead of World Malaria Day. REUTERS/Thierry Roge (ZAMBIA)