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Yellow Fever

Yellow fever is a reportable disease in Oklahoma. The disease is caused by the yellow fever virus, which belongs to the flavivirus group. Yellow fever is a viral disease that has caused large epidemics in Africa and the Americas. Infection causes a wide spectrum of disease, from mild symptoms to severe illness and death. The "yellow" in the name is explained by the jaundice that affects some patients. Yellow fever occurs in tropical regions of Africa and in parts of South America. The last epidemic of yellow fever in North America occurred in New Orleans in 1905.

Yellow fever is transmitted by the bite of infected mosquitoes. Humans and monkeys are the principal mammals infected. The virus is carried from one animal to another (horizontal transmission) by a biting mosquito (the vector). The mosquito can also pass the virus via infected eggs to its offspring (vertical transmission). The eggs produced are resistant to drying and lie dormant through dry conditions, hatching when the rainy season begins. Therefore, the mosquito is the true reservoir of the virus, ensuring transmission from one year to the next.  

Individuals with yellow fever may be viremic (have virus in their blood) for three to six days before demonstrating symptoms. Initial symptoms include fever and chills, severe headache, back pain, general muscle aches, nausea, fatigue, and weakness. This phase may be followed by a short period of symptom remission.

The toxic phase develops as the fever returns, with clinical symptoms including high fever, headache, back pain, nausea, vomiting, abdominal pain, and fatigue. Symptoms of bleeding include black vomit, nosebleed, gum bleeding, and purple pin-point spots (bruising).

In the late stages of disease, patients can develop hypotension, shock, kidney, and heat complications. Confusion, seizures, and coma can also occur. When epidemics occur in unvaccinated populations, death rates range from 15% to more than 50%. Symptoms of weakness and fatigue may last several months in people who recover. Those who recover from yellow fever generally have lasting immunity against subsequent infection.

Yellow fever is a disease that is caused by a virus that is spread to humans by the bite of an infected mosquito. This disease is only found in tropical and subtropical areas of the world, primarily South America and Africa. Therefore, only US residents that travel to these foreign countries are at risk for the disease. Yellow fever can be a fatal in approximately 20-50% of people that develop severe symptoms.

Yellow fever is a reportable disease in Oklahoma. 

Yellow fever can be prevented by vaccination. Travelers should get vaccinated for yellow fever before visiting areas where yellow fever occurs. Individuals are recommended to consult with their primary care physician or an international travel clinic at least three months prior to travel.

Avoid mosquito bites when traveling in tropical areas. Mosquitoes that spread yellow fever usually bite during the day, especially at dusk and dawn.

See your healthcare provider if you have visited an area where yellow fever is found and have symptoms of sudden onset fever, chills, severe headache, back pain, body aches, nausea, vomiting, fatigue, and weakness. 

There are no specific treatments that help patients with yellow fever. Resting, drinking plenty of fluids, and use of pain relievers and other medication to help bring down the fever are recommended. Whenever possible, yellow fever patients with severe disease should be hospitalized where they can be closely observed and receive any needed care. Aspirin and nonsteroidal anti-inflammatory drugs (e.g. ibuprofen, naproxen) should NOT be given to patients with yellow fever as these medications may increase the risk of bleeding in patients. Persons who recover from yellow fever generally have lasting immunity against any future infection with yellow fever.