Yellow Fever, Part 1

Summary

Yellow Fever is a viral tropical disease. It is most prevalent in equatorial Africa (90%) and South America (10%). No specific treatments exist but it can be prevented with a highly affective vaccine. The disease is spread via mosquito vectors (arbovirus). Yellow refers to the jaundice that occurs in severe infection from liver damage. Bleeding (hemorrhagic fever) and kidney damage are other severe manifestations.

Morbidity and Mortality

About 5% of people infected with the Yellow Fever virus will die. Foreign visitors to endemic countries are at the higher risk of severe infection if exposed. Hemorrhagic fever, liver failure, and other organ failures can lead to shock and death. It is very difficult to know how many infections occur annually but the WHO estimates about 200,000 (likely many more). Epidemics periodically occur and usually have worse than normal case fatality rates.

Story

Yellow fever outbreaks plagued the America’s in the 18th and 19th centuries, having been introduced from Africa just few hundred years prior. The Yellow Fever Epidemic of 1793 killed 9% of the residents in Philadelphia. Many, including George Washington, fled the city. Yellow Fever has plagued the US military for years before the 17D vaccine was discovered in 1937 by Max Theiler (Noble Prize). 

Key Points

1.  Yellow fever is endemic to equatorial Africa and South America, but strangely not Asia.

2.  People living and traveling to these areas should be vaccinated with the 17D live attenuated yellow fever vaccine.

3.  Fever, chills, headache, and myalgias are common. A minority of cases progress to liver failure and hemorrhage.  About half of cases that progress will be fatal

4. Treatment is supportive. As such, prevention with vaccine, vector control, and avoiding mosquito bites is very important. Avoid blood thinners and anti-platelets.

References

-       Keystone et al. Travel Medicine, 4th Ed. Elsevier 2019. Ch. 12. Torresi and Kollaritsch. Recommended/Required Travel Vaccines.

-       Farrar et al. Manson’s Tropical Diseases, 23rd Ed. Elsevier 2014. Ch. 14. Young et al. Arbovirus Infection.

-       Wikipedia. Yellow Fever, Yellow Fever Vaccine

-       WHO, Yellow Fever. https://www.who.int/news-room/fact-sheets/detail/yellow-fever

-       Vaccine Information Statement. CDC. https://www.cdc.gov/vaccines/hcp/vis/vis-statements/yf.pdf.

-       Thomas R. E. (2016). Yellow fever vaccine-associated viscerotropic disease: current perspectives. Drug design, development and therapy, 10, 3345–335

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