Yellow fever virus

Background

Microbiology

• RNA virus and member of the Flaviviridae family

Epidemiology

• Worldwide, about 200,000 cases and 30,000 deaths annually

Clinical Manifestations

• Spectrum of illness from asymptomatic to fatal
• Acute illness starts with fever, chills, headache, backache, myalgias, arthralgias, nausea, vomiting, photophobia, mild jaundice, and epigastric pain
• After the acute illness subsides, about 85% of infections are resolved, and 15% progress
• In those who progress, a brief remission of hours to days is followed by return of symptoms with progression to renal failure, hemorrhage, and thrombocytopenia

Vaccine-Related Disease

• Yellow fever vaccine-associated neurotropic disease, which includes meningoencephalitis, Guillain-Barré syndrome, and acute bulbar palsy
• Yellow fever vaccine-associated viscerotropic disease, which causes multi-organ failure similar to wildtype virus

	YEL-AND	YEL-AVD
Incubation period	7 to 21 days	2 to 5 days
Rate	0.8 per 100,000 doses	1 per 100,000 doses
Risk factors	age <6 months age >60-70 years	age >60 years thymus disease
Prognosis	full recovery	65% mortality

Management

• Supportive care

Prevention

• A live attenuated vaccine strain is available
• Contraindications
  • Allergy to any component of the vaccine
  • Infants less than 6 to 9 months of age, due to the high risk of neurotropic disease following immunization
  • People age 60 years and older, due to the high risk of adverse events following immunization
    • Booster doses may stll be given, if indicated
  • Pregnancy and breastfeeding
  • Thymus disease, including thymoma, thymectomy, and myasthenia gravis, given the high risk of viscerotropic disease
  • Moderate or severe acute illness
• Vaccination can cause YF vaccine-associated neurotropic disease and YF vaccine-associated viscerotropic disease