Epidemics of yellow fever struck the United States in the 18th and 19th centuries when it was carried in on ships arriving from the Caribbean. The disease attacked port cities as far north as Boston, including Philadelphia in 1793, but after 1822 it was restricted to the South. New Orleans, Mobile, Savannah and Charleston were hit hard; Memphis suffered terribly in 1878. Yellow fever epidemics caused terror, economic disruption and 100,000–150,000 deaths. Although yellow fever is no longer seen in the United States, travelers may be at risk in some areas of the world.

Yellow fever is an acute viral hemorrhagic disease caused by a virus related to the West Nile, St. Louis encephalitis and Japanese encephalitis viruses. It is endemic in tropical and subtropical areas of Sub-Saharan Africa and parts of Latin and South America. Yellow fever is spread through the bite of an infected female mosquito of the Aedes aegypti or Haemagogus species. Mosquitoes that feed on infected primates (human or non-human) carry the virus from one host to another, primarily between monkeys, from monkeys to humans, and from person to person. The mosquitoes breed in clean water, around houses (domestic), in the jungle (wild) or in both habitats (semi-domestic). Yellow fever cannot be transmitted by direct contact with an infected person.

Anyone can get yellow fever, but the elderly have a higher risk of severe infection. Each year there are an estimated 200,000 cases of yellow fever, causing 30,000 deaths worldwide. The number of cases increased over the past two decades due to declining population immunity, deforestation, urbanization, population movements and climate change.

Once a person is bitten by an infected mosquito, symptoms develop in three to six days. The disease progresses in three stages. Symptoms of Stage 1, or infection, include irregular heartbeat, headache, muscle and joint aches, fever, flushing, loss of appetite, dehydration, vomiting, possibly vomiting blood, and jaundice (which inspired the name “yellow fever”). Symptoms often go away after three or four days. In Stage 2, remission, fever and other symptoms go away. Most people recover at this stage, but others get worse within 24 hours. Stage 3, intoxication, involves the organs; people may experience shock; failure of the heart, liver or kidneys; bleeding disorders; gastrointestinal bleeding; secondary bacterial infections; seizures; delirium coma; and death. Up to 50 percent of those who develop severe illness die.

Inform your physician if you traveled to areas where the disease is known to thrive. Diagnosis is confirmed through a blood test for antibodies and a physical assessment. There is no specific treatment for yellow fever except supportive care in the hospital, which includes rest, pain management, intravenous fluids for hydration and blood transfusion for severe bleeding. In some cases, dialysis for kidney failure is needed.

Check with the Centers for Disease Control and Prevention for the status of the countries you are visiting; some require certificates of vaccination for entry. Yellow fever vaccine is available at designated vaccination centers, and it is considered safe and effective, although in rare cases serious side effects occur. A single dose provides protection for 10 years. The vaccine is not recommended for children under 9 months, pregnant women or people over 60. Those who are vaccinated receive a stamped and signed International Certificate of Vaccination or Prophylaxis (yellow card) which becomes valid 10 days after vaccination and is good for 10 years. Anyone at continued risk because of residence or travel should receive a booster dose every 10 years. Yellow fever vaccine can be administered at the same time as most other vaccines.

An outbreak of yellow fever began last September in the Darfur region of Sudan, placing 6 million people at risk. The World Health Organization is supporting the Ministry of Sudan to confront the outbreak.

Mosquito control is vital until vaccination takes effect. Yellow fever transmission in urban areas can be reduced by eliminating mosquito breeding sites and applying insecticides to water where they develop. Application of spray insecticides to kill adult mosquitoes during urban epidemics, combined with emergency vaccination campaigns, can reduce or halt disease transmission, buying time for vaccinated populations to build immunity. This kind of control is not possible in the jungle.

Tips for Travel to a Yellow Fever Zone

• Get vaccinated for yellow fever at least 10 days before travel.
• When outdoors, use an EPA-registered insect repellant containing DEET, picaridin, IR3535 or oil of lemon eucalyptus.
• To reduce mosquito bites, wear light-colored long sleeves, long pants and socks outdoors.
• Some mosquitoes bite through fabric. Spray clothing with EPA-registered repellant; clothing pretreated with permethrin is available.
• Stay in well-screened and air-conditioned areas. If you stay in camps or local hotels, use bed nets and mosquito coils.
• Beware of peak mosquito feeding hours, usually from dusk to dawn; however, the Aedes aegypti feeds during the day.

The content of this article is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.