Yellow fever reach the stomach of the mosquito, and if the virus concentration is high enough, the virions can infect epithelial cells and replicate there. From there, they reach the haemocoel (the blood system of mosquitoes) and from there the salivary glands. When the mosquito next sucks blood, it injects its saliva into the wound, and the virus reaches the bloodstream of the bitten person. Transovarial and transstadial transmission of the yellow fever virus within "A. aegypti", that is, the transmission from a female mosquito to her eggs and then larvae, are indicated. This infection of vectors without a previous blood meal
Yellow fever probably due to the genetic morphology of the immune system. Another possible side effect is an infection of the nervous system, which occurs in one in 200,000 to 300,000 cases, causing yellow fever vaccine-associated neurotropic disease, which can lead to meningoencephalitis and is fatal in less than 5% of cases. The Yellow Fever Initiative, launched by WHO in 2006, vaccinated more than 105 million people in 14 countries in West Africa. No outbreaks were reported during 2015. The campaign was supported by the GAVI Alliance, and governmental organizations in Europe and Africa. According to the WHO, mass vaccination cannot eliminate