How Do People Know They Have Yellow Fever?

After an incubation* period of three to six days, the yellow fever virus begins to produce symptoms. An carly phase of disease occurs, which includes fever, headache, muscle aches, and vomiting. The infected person may have a slower heartbeat than that expected with a high fever. After a few days, most of the symptoms disappear. Many people recover from yellow fever at this point without complications. However, about 15 percent of patients develop a second, toxic phase of the disease, in which fever reappears and the disease becomes more severe. Inflammation of the liver occurs, along with jaundice, stomach pains, and vomiting. The mouth, nose, eyes, and stomach can bleed uncontrollably, with blood present in vomited material and bowel movements. The kidneys may begin to fail, and patients may go into a coma (an unconscious state in which a person cannot be awakened).

How Do Doctors Diagnose and Treat Yellow Fever?

Early stages of yellow fever can be casily confused with other diseases such as malaria, typhoid fever, and other hemorrhagic (heh-muh-RAH-jik) fevers and types of viral hepatitis*. Blood tests can detect whether a patient's body has produced yellow fever antibodies* to fight the infection. Doctors also will take a travel history to see if a patient recently has visited a country where yellow fever occurs.

No specific treatment exists for yellow fever. Care is geared toward treating complications of the disease. In serious cases, intensive care in the hospital usually is needed. Patients may be given fluids to prevent dehydration, and blood transfusions may be necessary if bleeding is severe.

Most people who contract yellow fever recover from the early phase of the discase within a week; those who progress to the toxic phase may take several weeks or longer to recover. About half of those who develop toxic phase symptoms die within two weeks; the other half may recover without significant long-term problems.

How Can Yellow Fever Be Prevented?

Vaccination against yellow fever is the single most important prevention measure, and it is a must for people traveling to countries where the disease is common. Most countries in which yellow fever occurs require a certificate proving that travelers have been vaccinated before they are allowed into the country. One dose of vaccine provides at least 10 years of immunity.

Doctors recommend that infants under six months of age, pregnant women, people allergic to eggs (eggs are used in producing the vaccine), and people with a weakened immune system (such as people who have AIDS or certain cancers) not receive the vaccine; these people are advised to delay visits to countries where yellow fever is endemic.

Avoiding mosquito bites when traveling abroad reduces the risk of contracting yellow fever. To help prevent infection, experts suggest that travelers do the following:

* Wear long sleeves and pants

* Avoid going outside when mosquitoes are active-at dawn, dusk, and early evening

* Use mosquito repellent

* Sleep beneath a mosquito net

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