Most of the cases of the mosquito-borne disease have occurred in Goias, Brasilia and Matto Grosso do Dul states, Mercopress reported Saturday. The first case to be confirmed by laboratory tests was Dec. 17, the news agency said.

WHO says the outbreak follows cases detected in monkeys in April 2007.

Brazil has suspended the export of yellow fever vaccine from Bio-Manguinhos, based in Brazil, to meet the country's needs in view of the outbreak, Mercopress said. Last month, Brazilian health officials requested an additional 4 million doses of the vaccine from global stockpiles, with the intent of vaccinating millions of people in the target states this month.

Paraguayan authorities also have issued yellow fever alerts, with at least one death suspected to have been caused by the disease and as many as 150 other possible cases reported.