20 Interesting Facts About Yellow Fever + Symptoms, Causes, Prevention

Here are the top interesting facts about yellow fever:

#1 Yellow fever (YF) is an acute viral hemorrhagic disease usually transmitted by infected mosquitoes. It is caused by a virus of the Flavivirus genus of the Flaviviridae family.

#2 This virus cannot be passed directly from one infected human being to another. Also, after having it once, an individual is generally immune, meaning that he is unlikely to have it again.

#3 The theory that YF is transmitted by a mosquito was first introduced by Dr. Carlos Finlay, a Cuban physician, in the late 19th century.

However, only in 1900, Dr. Walter Reed, a US Army major (using Dr. Carlos Finlay’s research), proved that YF was actually transmitted by mosquitoes.

#4 YF usually occurs in tropical areas of South America and Africa, and every year there are about 200,000 cases of YF worldwide. This leads to more than 30,000 deaths.

#5 Infection is more frequent during the late rainy and early dry seasons in Africa and during hot, rainy, humid months in South America.

#6 The first recorded epidemic of YF was in 1648 in the Yucatan Peninsula (southeastern Mexico), and it was part of a larger epidemic involving many Caribbean Islands.

#7 In the late 1700s, New England and few other port cities in North America suffered severe ZF outbreaks, including the outbreak in Philadelphia in 1793 which killed about 10 percent of its population.

#8 2,200 deaths were reported in Cadiz, Spain. Furthermore, outbreaks in British and French seaports followed soon after. Also, between the years 1817 and 1905, about 41,000 people died from YF in New Orleans.

#9 Moreover, YF caused difficulties for the United States Army in Cuba during the Spanish-American War (which resulted in the U.S. acquisition of territories in Latin America and the western Pacific). Apparently, more soldiers died of YF than in battle.

#10 In Africa, in the 1980s, the incidence of YF outbreaks increased by thirty percent, and the case-fatality rate to be 25%. For example, between 1980 and 2012, the World Health Organization reported 150 YF outbreaks in 26 African countries in Africa.

#11 Presently, YF outbreaks appear to be on the rise internationally, most likely because of deforestation, a decreased immunity to infection among local populations, high-density urbanization, and climate change.


#12 During the first 3 to 6 days (the incubation period) after an individual contracted YF, he won’t experience any symptoms or signs. After this incubation period is over, the infection enters an acute phase, and symptoms include:

  • backaches;
  • shivers;
  • loss of appetite;
  • flushing;
  • fever;
  • joint aches;
  • muscle aches;
  • headaches.

#13 Approximately 15% of the sufferers enter a 2nd stage, known as the toxic stage. The symptoms and signs are considerably more severe, and include:

  • bleeding from the mouth, nose, and eyes;
  • irregular heartbeats;
  • kidney and liver failure;
  • jaundice, also known as icterus, which is a yellowish or greenish pigmentation of the sclerae (the white part of the eye) and skin;
  • abdominal pain;
  • delirium, fever, seizures, and occasionally coma;
  • sluggishness, tiredness, and lethargy.


#14 YF is caused by a virus which is spread by the Aedes aegypti mosquito (this mosquito can also spread chikungunya, dengue fever, Mayaro, or Zika fever).

#15 This type of mosquito thrives in and near human habitations. Most cases of YF occur in tropical South America and sub-Saharan Africa. Anyone can get it (in these areas), however, the elderly have a higher chance to experience the toxic stage.


#16 This infection may be quite difficult to tell apart from other similar conditions, particularly in the early stages.

To be 100 percent sure, a healthcare professional will take a blood sample and test it with polymerase chain reaction (a method to make many copies of a specific DNA region).


#17 Treatment is commonly directed at reducing the symptoms until the infection completes its course. Also, a doctor can also use dialysis (in case of kidney failure), fluids through a vein (to prevent dehydration due to high fever), or blood products (in case of severe bleeding).

#18 More importantly, the treatment should avoid certain medicines, like – an aspirin or other nonsteroidal anti-inflammatory drugs (naproxen or ibuprofen), that may actually increase the risk of bleeding.


#19 If you’re traveling in a country where YF is found, try to avoid being bitten by mosquitoes.

You can do this by using insect repellent containing 50% DEET and mosquito nets. If weather permits, it is recommended to wear long pants and socks when going outdoors. Also, spray your clothes with appropriate repellent for extra protection.

#20 Avoid being unprotected at dusk or dawn (outdoors) since this is the time when female mosquitoes tend to feed.

Images credit – Shutterstock

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