Yellow fever seems to play a role in single, sudden breakouts of the disease. Three epidemiologically different infectious cycles occur, in which the virus is transmitted from mosquitoes to humans or other primates. In the "urban cycle", only the yellow fever mosquito "A. aegypti" is involved. It is well adapted to urban areas, and can also transmit other diseases, including Zika fever, dengue fever, and chikungunya. The urban cycle is responsible for the major outbreaks of yellow fever that occur in Africa. Except for an outbreak in Bolivia in 1999, this urban cycle no longer exists in South America. Besides the urban
2012 yellow fever outbreak in Darfur, Sudan 2012 yellow fever outbreak in Darfur, Sudan In late 2012, a yellow fever outbreak occurred in the Darfur region of Sudan that was the largest yellow fever epidemic to strike Africa in two decades. On 10 January 2013, the Sudan Federal Ministry of Health and the World Heath Organization (WHO) reported that there had been 847 suspected cases since 2 September 2012, including 171 deaths, for an estimated case fatality rate of 20%. A mass vaccination campaign was launched in mid-November. By early January, the five states of Darfur were free of any new cases. The first cases of yellow