Scottsdale, Arizona - The spread of yellow fever, which kills an estimated 60,000 people a year, has global health officials concerned. The World Health Organization says the first imported case of yellow fever to China has been reported. Globally, yellow fever cases have been decreasing over the past 10 years since the launch of Yellow Fever Initiative; however, Angola is experiencing its largest outbreak of the mosquito-borne illness in 30 years.

Mayo Clinic infectious diseases specialist Dr. Pritish Tosh says, "Yellow fever is a viral infection that is spread through the bite of Aedes aegypti mosquitoes. It can be severe including fatal complications. Areas of the world where we see yellow fever include parts of Africa and South America."

Dr. Tosh says yellow fever is preventable. "There is a vaccine available and travelers who are going to yellow fever endemic areas of the world need to get the vaccine because it can prevent a severe and possible fatal infection."

In mild cases, yellow fever causes fever, headache, nausea and vomiting. More serious cases can result in heart, liver and kidney problems, along with bleeding (hemorrhaging). Up to 50 percent of people with the more severe form of yellow fever die of the disease.

Currently, there are no treatments available. Dr. Tosh says there is no anti-viral treatment for yellow fever. "Offering supportive care is the only way to help a patient who has yellow fever, so getting a vaccine is the best way to ensure the illness is avoided."