Yellow fever is a viral infection that manifests as serious, possibly deadly, flu-like symptoms. It is an extremely rare condition in the United States, with no cases being reported throughout the entire country in 2015.
It is far more common in areas of South America and Africa, as those regions are breeding grounds to the species of mosquito that is usually the carrier of the disease. As such, it is highly recommended that travelers receive vaccinations before their trip.
Yellow fever sets in quickly, often after an incubation period of less than a week. The infection is initially mild before moving to the acute phase, at which point symptoms will become more severe for a few days. Many will recover after this, although older adults and patients with compromised immune systems are more prone to developing life-threatening complications.
The World Health Organization estimates that about half of the people who reach this stage this will die.
Yellow fever usually causes similar symptoms across the board, though severity may vary from case to case.
The most severe infections have been known to cause fatal conditions affecting the liver, kidney, and heart.
The cause for yellow fever are the mosquitoes in certain parts of the world that are infected with a flavivirus. This virus is then transferred to human beings and other primates, such as monkeys and chimpanzees. The Aedes aegypti mosquito is the primary vector for the yellow-fever virus, although some species of Haemogogus mosquitoes may also carry the disease.
Commonly called the yellow-fever mosquito, only the adult females can transmit this disease. They become infected with the yellow-fever pathogen when they bite infected people or other primates, and they transmit the disease by biting another primate. Unlike other mosquito species that typically bite at dawn, dusk, or nighttime, the yellow-fever mosquito is indiscriminate about the time of day it bites.
Sylvatic (jungle) yellow fever, intermediate yellow fever, and urban yellow fever are all caused by mosquito bites, but they are differently named because of the habitats of the mosquitoes – sylvatic mosquitoes are found in rainforests, intermediate types live in households and in the wild, and urban types are found in highly populated areas.
Though it is preventable with a vaccine, there are no treatments available specifically for yellow fever.
Rather, the focus shifts to symptom management while the body fights off the virus on its own. Increased fluid intake is important to combat dehydration, and medications can be prescribed to treat any other infections that might develop. Patients with more severe complications may require oxygen, blood transfusions, and dialysis.
The yellow fever vaccine prevents this disease. A single dose provides a lifetime of immunity without requiring a second shot, except for at-risk people for whom a 10-year booster shot is recommended.
The shot must be administered 30 days before traveling to a known endemic region, which include some areas in Africa (particularly the sub-Saharan region), tropical South America and Central America, as well as certain Caribbean locales. The disease may also be transmitted in 23 states where the yellow-fever mosquito is found.
Areas of most concern include Southern Florida and the Gulf Coast areas of Texas and Louisiana.
In addition to the yellow fever vaccine, preventive measures include avoiding habitats favored by mosquitoes, eliminating areas of standing water in countries where mosquitoes carrying yellow fever can be found, wearing clothing that covers exposed skin, and applying an insect repellent to skin and clothing that contains DEET.