TNF and Thrombocytopenia: The major components of the immune responses to YFV infection include TNF-α, TGF-β and IFN-γ and these (especially TGF-β) are related to apoptosis and the various symptoms or signs observed in severe disease such as vascular leak syndrome, thrombocytopenia, aminotransferase abnormalities, vomiting and hemorrhagic diathesis [29].