A yellow fever outbreak in Sudan's Darfur region has killed 107 people in the last six weeks, the World Health Organization reported Tuesday, warning that the disease could spread all over the country.

The number of deaths from the outbreak is steadily rising, and Sudan is working on an emergency vaccination drive. Officials reported last week that 67 people had died in the outbreak.

There is no medicinal cure for yellow fever, which is spread by mosquitoes. Doctors treat the main symptoms -- dehydration, fever, bleeding and vomiting -- and wait for the viral infection to pass.