Yellow fever is a viral infection spread by a particular species of mosquito. It's most common in areas of Africa and South America, affecting travelers to and residents of those areas.
In mild cases, yellow fever causes fever, headache, nausea and vomiting. But yellow fever can become more serious, causing heart, liver and kidney problems along with bleeding (hemorrhaging). Up to 50 percent of people with the more severe form of yellow fever die of the disease.
There's no specific treatment for yellow fever. But getting a yellow fever vaccine before traveling to an area in which the virus is known to exist can protect you from the disease.
During the first three to six days after you've contracted yellow fever — the incubation period — you won't experience any signs or symptoms. After this, the virus enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.
These signs and symptoms usually improve and are gone within several days.
The toxic phase of yellow fever can be fatal.
When to see a doctor
Seek emergency medical care if you've recently traveled to a region where yellow fever is known to occur and you develop severe signs or symptoms of the disease. If you develop mild symptoms, call your doctor.
Yellow fever is caused by a virus that is spread by the Aedes aegypti mosquito. These mosquitoes thrive in and near human habitations where they breed in even the cleanest water. Most cases of yellow fever occur in sub-Saharan Africa and tropical South America.
Humans and monkeys are most commonly infected with the yellow fever virus. Mosquitoes transmit the virus back and forth between monkeys, humans or both. When a mosquito bites a human or monkey infected with yellow fever, the virus enters the mosquito's bloodstream and circulates before settling in the salivary glands. When the infected mosquito bites another monkey or human, the virus then enters the host's bloodstream, where it may cause illness.
You may be at risk of the disease if you travel to an area where mosquitoes continue to carry the yellow fever virus. These areas include sub-Saharan Africa and tropical South America.
Even if there aren't current reports of infected humans in these areas, it doesn't mean you're risk-free. It's possible that local populations have been vaccinated and are protected from the disease, or that cases of yellow fever just haven't been detected and officially reported.
If you're planning on traveling to these areas, you can protect yourself by getting a yellow fever vaccine at least 10 to 14 days before traveling.
Anyone can be infected with the yellow fever virus, but older adults are at greater risk of getting seriously ill.
Yellow fever results in death for 20 to 50 percent of those who develop severe disease. Death usually occurs within two weeks from the start of infection. Complications during the toxic phase of a yellow fever infection include kidney and liver failure, jaundice, delirium and coma.
People who survive the infection recover gradually over a period of several weeks to months, usually without significant organ damage. During this time a person may experience fatigue and jaundice. Other complications include secondary bacterial infections, such as pneumonia or blood infections.
Preparing for your appointment
Call your doctor if you've recently returned from travel abroad and develop mild symptoms similar to those that occur with yellow fever. If your symptoms are severe, go to an emergency room or call 911 or your local emergency number.
Here's some information to help you get ready, and know what to expect from your doctor.
Information to gather in advance
The list below suggests questions to raise with your doctor about yellow fever. Don't hesitate to ask more questions during your appointment at any time that you don't understand something.
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.
What to expect from your doctor
Tests and diagnosis
Diagnosing yellow fever based on signs and symptoms can be difficult because early in its course, the infection can be easily confused with malaria, typhoid, dengue fever and other viral hemorrhagic fevers.
To diagnose your condition, your doctor will likely:
If you have yellow fever, your blood may reveal the virus itself. If not, blood tests known as enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) also can detect antigens and antibodies specific to the virus. Results of these tests may not be available for several days.
Treatments and drugs
No antiviral medications have proved helpful in treating yellow fever. As a result, treatment consists primarily of supportive care in a hospital. This includes providing fluids and oxygen, maintaining adequate blood pressure, replacing blood loss, providing dialysis for kidney failure, and treating any other infections that develop. Some people receive transfusions of plasma to replace blood proteins that improve clotting.
If you have yellow fever, you may also be kept away from mosquitoes, to avoid transmitting the disease to others.
A single dose of the vaccine provides protection for at least 10 years. Side effects of the yellow fever vaccine are usually mild, lasting five to 10 days, and may include headaches, low-grade fevers, muscle pain, fatigue and soreness at the site of injection. More-significant reactions — such as developing a syndrome similar to actual yellow fever, inflammation of the brain (encephalitis) or death — can occur, most often in infants and older adults. The vaccine is considered safest for those between the ages of 9 months and 60 years.
Talk to your doctor about whether the yellow fever vaccine is appropriate if your child is younger than 9 months, if you have a weakened immune system (immunocompromised), or if you're older than 60 years.
To reduce your exposure to mosquitoes:
To ward off mosquitoes with repellent, use both of the following:
According to the Centers for Disease Control and Prevention, oil of lemon eucalyptus, a more natural product, offers the same protection as DEET when used in similar concentrations. However, these products should not be used on children younger than age 3.
Last Updated: 2011-08-27
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