Review Question - QID 108952

The patient in this vignette presents with fever, jaundice, and black vomitus suggestive of yellow fever. Yellow fever is caused by an enveloped (+) ssRNA flavivirus.

In this patient with fever, jaundice, and black vomitus, the differential diagnosis includes yellow fever, viral hepatitis, Dengue fever, malaria, and other hemorrhagic fevers (e.g., Ebola, Lassa, and Marburg). In an unvaccinated patient who went on a recent trip to Africa and expired from his illness, yellow fever is the most likely diagnosis. Clinically, yellow fever presents with an incubation period of 3-6 days followed by a mild phase of fever, headache, nausea, vomiting, and myalgias. This eventually progresses to a severe late phase of high fever, liver damage/jaundice, bleeding diathesis, bloody vomitus, and death. Yellow fever can be differentiated from other hemorrhagic fevers by the presence of jaundice. Liver biopsy in these patients may reveal eosinophilic Councilman bodies; however, liver biopsy is contraindicated in these patients due to bleeding risk. The diagnosis is based on serology findings showing IgM directed against the virus.

Illustration A reveals the characteristic appearance of Councilman bodies. These are well-demarcated eosinophilic inclusions that represent intracellular condensations of cytoplasm. They are predominantly found in zone II hepatocytes. Councilman bodies are not specific to yellow fever, as they can be seen in other causes of viral hepatitis.

Incorrect Answers:
Answer 2: The togavirus family includes rubella and several equine encephalitis viruses. Of these, rubella is most commonly tested. Rubella presents with a mild measles-like disease (fever, lymphadenopathy, and a maculopapular rash extending from the forehead to the extremities).

Answer 3: Norwalk virus is a member of the calicivirus family. Norwalk virus presents with acute watery diarrhea, nausea, and vomiting that resolves spontaneously in normal hosts.

Answer 4: Hantavirus is the most commonly tested bunyavirus. It presents with pulmonary edema, cough, fever, myalgias, thrombocytopenia, and hypotension. It can be differentiated from yellow fever by history because the reservoir for hantavirus are rodents in the southwestern United States.

Answer 5: Hepatitis E virus is the most commonly tested hepevirus. It presents as a mild acute hepatitis but can be fatal in pregnant women.

Bullet Summary:
Yellow fever is caused by an enveloped (+) ssRNA flavivirus and is transmitted by the Aedes mosquito to individuals traveling to or residing in Africa. It presents with high fever, black vomitus, jaundice, and severe infectious symptoms.