Yellow fever is a mosquito-borne viral infection of the Flaviviridae family. The disease is endemic to equatorial regions of Africa, South America, and Central America. The mortality rate of yellow fever in general is 8%; however, patients that develop severe disease have a mortality rate of 20%-50%.

Although the use of yellow fever as an agent of bioterrorism is unlikely, in a bioterrorist attack it would most likely be dispersed as an aerosol; the release of infected mosquitoes is also feasible. Mosquitoes serve as the natural reservoir and vector: Aedes spp. in Africa and Haemagogus and Sabethes spp. in South America.

The incubation period of yellow fever is 3-6 days, and many cases are mild or asymptomatic. Symptomatic patients experience a sudden onset of fever, chills, myalgia, headache, facial flushing, prominent low back pain, conjunctival redness, loss of appetite, and nausea / vomiting, which lasts for 3-4 days. This is followed by a period of remission with resolution of symptoms for 48 hours, and approximately 85% of patients will clear the infection at this stage.

The remaining 15% of patients will develop a hemorrhagic disease consisting of hepatitis, jaundice, abdominal pain, vomiting, petechiae, and hemorrhaging from the mouth, nose, eyes, and gastrointestinal tract. Renal dysfunction often occurs resulting in anuria. 50% of patients in the toxic phase will die within 2 weeks. Those who recover experience months of fatigue and have lasting immunity to reinfection.

Person-to-person transmission is not possible.

A vaccine for yellow fever is available. Refer to Management Pearls.