Yellow fever is a mosquito-borne viral disease that occurs mainly in the tropics.
Yellow fever occurs only in the tropical areas of Central Africa, southern Panama, and South America.
Some people with yellow fever have no or mild symptoms, but others have more severe symptoms such as yellow skin (jaundice), fever, headache, muscle aches, and bleeding.
Doctors diagnose yellow fever by growing (culturing) the virus, by doing blood tests to detect antibodies to the virus, or by using polymerase chain reaction (PCR) techniques to help identify the virus's genetic material.
Treatment is mainly supportive and includes medications to treat or prevent bleeding.
A vaccine is available for use by people residing in endemic countries and for travelers to areas where yellow fever is common, but avoiding mosquito bites is also important.
Yellow fever is caused by a flavivirus that is spread by mosquitoes.
Yellow fever is one of the most easily recognized and historically important viral infections. In the past, major epidemics of yellow fever caused tens of thousands of deaths. Once common in tropical and temperate zones around the world, the disease now occurs only in the tropical areas of Central Africa, southern Panama, and South America. Infection is more common during hot, rainy, humid months in South America and during the late rainy and early dry seasons in Africa.
Symptoms of Yellow Fever
Some infected people do not have symptoms. Others have mild symptoms, and some have a severe, life-threatening illness.
Symptoms of yellow fever usually appear about 3 to 6 days after being bitten by an infected mosquito. The first symptoms are headache, dizziness, muscle aches, chills, and mild fever, which begin suddenly. Nausea, vomiting, constipation, extreme fatigue, irritability, and restlessness are common. The face is flushed.
All of these symptoms subside after a few days. Some people then recover, but others develop a high fever, nausea, vomiting, and severe generalized pain a few hours or days after the initial symptoms subside. The skin turns yellow (jaundice) because the liver is infected. Often, there is bleeding from the nose, mouth, and gastrointestinal tract. People may vomit blood. They may become confused and apathetic.
Some people become delirious. They have very low blood pressure (shock). Severe infection can cause seizures, malfunction of several organs, and coma may occur; 30 to 60% of people with severe bleeding and fever die.
Diagnosis of Yellow Fever
Culture or blood tests
Doctors suspect yellow fever when people living in an area where the infection is common have typical symptoms.
Yellow fever is diagnosed by growing (culturing) the virus or detecting antibodies to the virus in the blood. Or polymerase chain reaction (PCR) techniques may be used to make many copies of the virus's genetic material. This technique enables doctors to rapidly and accurately identify the virus.
Treatment of Yellow Fever
Supportive care
Treatment of yellow fever involves supportive care, including medications to treat or prevent bleeding, such as injections of vitamin K (which can help blood clot).
There is no specific treatment for yellow fever.
Prevention of Yellow Fever
Prevention of yellow fever involves
Avoiding mosquito bites
Vaccination
Isolation
Avoiding mosquito bites is key to prevention. People who live in or visit areas where yellow fever is common can
Apply DEET (diethyltoluamide) insect repellant to the skin.
Use mosquito netting.
Wear long-sleeved shirts and long pants.
Stay in places that have air conditioning or that use window and door screens to keep mosquitoes out.
For children, the following precautions are recommended:
Do not use insect repellent on infants under 2 months old.
Do not use products containing oil of lemon eucalyptus (para-menthane-diol) on children under 3 years old.
For older children, adults should spray repellent on their own hands and then apply it to the children's skin.
Dress children in clothing that covers their arms and legs, or cover the crib, stroller, or baby carrier with mosquito netting.
Do not apply insect repellent to the hands, eyes, mouth, or cut or irritated skin of children.
A vaccine that is 95% effective at preventing yellow fever is available. A single dose of vaccine can provide life-long immunity against yellow fever. People should be given the vaccine at least 10 days before traveling to a yellow fever endemic country. In the United States, the vaccine is given only at yellow fever vaccination clinics authorized by the U.S. Public Health Service. However, there are many such centers (see CDC: Yellow Fever Vaccination Clinics).
Many countries require vaccination only for travelers coming into their country from areas where yellow fever occurs. If people are traveling to areas where yellow fever is common, they should be vaccinated.
The occurrence of death in monkeys due to yellow fever often indicates that jungle outbreaks are occurring with the risk of spillover to people. Unvaccinated people in these regions should evacuate the area until they are immunized. Prompt mass yellow fever vaccination of the population is used to control an ongoing yellow fever outbreak through immunization.
The vaccine is not given to
Pregnant women
Infants under 6 months old
People with a weakened immune system, such as those with AIDS
If the infection is suspected or diagnosed, people are isolated in rooms that are screened and sprayed with insecticides to prevent further spread of the virus by mosquitoes.
