The World Health Organization (WHO) begins a weeklong campaign on Saturday to vaccinate nearly six million people against yellow fever across the southern half of Mali. This is the first time that a mass vaccination campaign will be undertaken, using medicines from a developing country. A Brazilian manufacturer will supply half of the needed vaccines. Lisa Schlein reports for VOA from WHO headquarters in Geneva.

Tens of thousands of volunteers will fan across southern Mali over the next week. The mass campaign aims to protect millions of people from one of the world's most infectious diseases.

Yellow fever is an acute viral disease, spread to humans by infected mosquitoes. In a telephone interview from Bamako, Mali, World Health Organization (WHO) spokesman Gregory Hartl tells VOA yellow fever causes death in about 15 percent of infected people.

"In rapidly urbanizing areas in Africa and in Latin America, we have quite a few areas which are under-vaccinated and are rapidly growing," he said. "If yellow fever were to get into these urban areas, we could see huge outbreaks. So, there is an imperative to vaccinate people, to get vaccination levels up to a point where there is community immunity to the disease."

The northern part of Mali is largely desert. So, conditions do not exist there for spreading the disease. But, the southern part of the country is ripe for transmission of yellow fever.

Over the next week, six million people, nearly 1 million people a day in 33 districts, will be vaccinated by local health teams and volunteers.

Hartl says the goal is to reach 80 percent vaccination coverage for the total population. He says this will ensure immunity against yellow fever in all the at-risk areas of Mali.

"There is no treatment per se or drug that one can take after the fact," he added. "However, before the fact, we have a yellow fever vaccine which is one of the most efficient, safest vaccines that the world has for any disease. So, this is why vaccinating people is so important for us. Because once a person is vaccinated, you have immunity against yellow fever for at least seven years if not for life."

Hartl says the vaccine causes no adverse side effects. He says WHO hopes Yellow Fever vaccination will one day become part of routine immunization programs.

Mali is the third country, after Togo and Senegal, to undertake a national preventive vaccination campaign. WHO says other countries will follow suit as soon as sufficient vaccine is available. Currently, 610 million people in Africa are considered to be at-risk from the disease.