Yellow fever

Abstract

The yellow fever (YF) virus is a Flavivirus, transmitted by Haemagogus, Sabethes or Aedes aegypti mosquitoes. The disease is endemic in forest areas in Africa and Latin America leading to epizootics in monkeys that constitute the reservoir of the disease. There are two forms of YF: sylvatic, transmitted accidentally when approaching the forests, and urban, which can be perpetuated by Aedes aegypti. In Brazil, the last case of urban YF occurred in 1942. Since then, there has been an expansion of transmission areas from the North and Midwest regions to the South and Southeast. In 2017, the country faced an important outbreak of the disease mainly in the states of Minas Gerais, Espírito Santo and Rio de Janeiro. In 2018, its reach extended from Minas Gerais toward São Paulo. Yellow fever has an incubation period of 3 to 6 days and sudden onset of symptoms with high fever, myalgia, headache, nausea/vomiting and increased transaminases. The disease ranges from asymptomatic to severe forms. The most serious forms occur in around 15% of those infected, with high lethality rates. These forms lead to renal, hepatic and neurological impairment, and bleeding episodes. Treatment of mild and moderate forms is symptomatic, while severe and malignant forms depend on intensive care. Prevention is achieved by administering the vaccine, which is an effective (immunogenicity at 90-98%) and safe (0.4 severe events per 100,000 doses) measure. In 2018, the first transplants in the world due to YF were performed. There is also an attempt to evaluate the use of active drugs against the virus in order to reduce disease severity.

Yellow fever: profile of cases and factors associated with death in a hospital in the State of Rio de Janeiro, 2017–2018

“…In this and in the two other studies 15 , 19 , AST increases generally exceeded those of ALT, which is described in the literature 5 , 23 probably due to the cytopathic effect of the virus on the myocardium and skeletal muscles; ALT is more specific for liver disease than AST. Regarding the increased bilirubin level, it was mainly due to the increase in direct-reacting fraction, in agreement with the literature 5 .…”

“…No specific treatment has been defined so far. Hospitalization of severe forms is recommended in hospitals that offer intensive care and dialysis 1 , 2 , 23 . Some antiviral drugs have been evaluated, such as ribavirin, thiazofurine, carboxamide, and pyrazoline compounds 4 , 22 , and more recently, sofosbuvir 7 .…”

Detection of Yellow Fever Virus in Sylvatic Mosquitoes during Disease Outbreaks of 2017–2018 in Minas Gerais State, Brazil

“…A total of 779 cases were confirmed with 262 deaths in 2016/2017, and 1376 confirmed cases with 483 deaths in 2017/2018 [8]. This increase in the number of cases may be related to factors such as low vaccination coverage and viral circulation in regions where it previously did not occur as well as changes in the viral genotype [9,10].…”

Yellow Fever

“…In severe cases, there may be marked leukocytosis, significantly high aminotransferases and change in coagulation factors, mainly prothrombin, factor VIII and thromboplastin 11,16 . Both creatinine and urea levels can rise and their worsening correlates with deterioration of patient's condition 17 . Urinalysis can show bilirubinuria, hematuria, and marked proteinuria, with values above 500 mg/100 mL of urine 11 .…”