The Centers for Disease Control has confirmed an outbreak of yellow fever in Sudan, with 849 confirmed cases and 171 deaths reported to date.
The outbreak began on Nov. 16 and was swiftly followed by a Nov. 20 mass vaccination campaign in 12 highly affected localities with a total population of 2.2 million.
The majority of cases have been recorded in central, south and west Darfur, according to Sudan's Federal Ministry of Health.
Yellow fever virus is considered one of the most virulent and pantropic flaviviruses, which is a genus including dengue, West Nile, Japanese encephalitis and tick-borne encephalitis viruses, which are arthropod-borne.
In the early phase of yellow fever virus, symptoms include fever, severe muscle pain, headache, chills, anorexia, and nausea and vomiting.
The majority of patients recover after three to six days, but 15 to 25 percent enter a more toxic second phase within 24 hours of initial remission. This is signaled by high fever and an acute fulminant hepatitis with rapid deterioration of liver function and severe abdominal pain. Bleeding may occur anywhere in the gastrointestinal tracts, kidney function deteriorates, myocarditis occurs, and encephalopathy with stupor or coma may follow.
Despite the existence of an effective yellow fever vaccine, the disease is endemic in tropical areas of South America and Africa.