GENEVA, April 11 (Reuters) - A Brazilian drugs manufacturer is supplying yellow fever vaccines to Mali to support the world's first "south-south" mass vaccination campaign, the World Health Organisation (WHO) said on Friday.

Nearly half of the West African country's 12 million people will receive vaccines during the week-long campaign beginning on Saturday, the WHO said.

The campaign will involve one of the largest shipments of vaccinations from one developing country to another, with Rio de Janeiro-based Bio-Manguinhos providing half of the doses used.

Adamou Yada, the WHO's regional adviser for communicable disease surveillance and response in Africa, said the Brazilian vaccines had helped ease strain on the global supply of yellow fever shots following recent outbreaks in Latin America.

"We are much more able to meet supply demands both for emergency and routine vaccination, and this first mass shipment of vaccine from one developing country to another is proof of that," he said in a statement released in Geneva.

Around 610 million people in Africa are considered to be at risk from yellow fever, an often-deadly viral disease transmitted by mosquitoes for which there is no specific treatment.

Because of its severity and the potential for epidemics, a single case of yellow fever is considered a public health threat.

The WHO said the risk of yellow fever outbreaks in Mali "will be greatly reduced" after the vaccination campaign.

Most of the world's vaccine manufacturers are based in developed economies such as the United States, Britain and France -- France's Sanofi Pasteur <SASY.PA> will provide the other half of the campaign's vaccinations.

The Global Alliance for Vaccinations and Immunisations (GAVI), a Geneva-based health financing venture supported by the Bill & Melinda Gates Foundation, has provided $58 million to help cut the risk of yellow fever transmission in West Africa.

Togo and Senegal have already carried out similar preventive vaccination campaigns. (Reporting by Laura MacInnis; Editing by Stephanie Nebehay and Chloe Fussell)

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