Many cases of yellow fever are not diagnosed correctly because they occur in areas where dengue and chikungunya are endemic. Mild yellow fever symptoms are similar to both dengue and chikungunya. If jaundice develops, hepatitis is typically believed to be the cause.
Serum can be tested at the CDC for IgM antibodies and plaque neutralizing antibodies. The virus can sometimes be cultured if blood is collected early enough in the disease.