Yellow Fever

About This Disease

Yellow Fever is a disease caused by a virus that is found in tropical and subtropical areas in South America and Africa.  The virus is spread to people by the bite of an infected mosquito.  Yellow fever is a very rare cause of illness in U.S. travelers.

Signs and Symptoms

Most people infected with yellow fever virus will either not have symptoms, or have mild symptoms and completely recover.

Some people will develop yellow fever illness with initial symptoms including:

  • Sudden onset of fever
  • Chills
  • Severe headache
  • Back pain
  • General body aches
  • Nausea
  • Vomiting
  • Fatigue (feeling tired)
  • Weakness

Most people with the initial symptoms will improve within one week.  For some people who recover, weakness and fatigue may last several months.

A few people (1 out of 7) will develop a more severe form of the disease.  After the initial symptoms, there will be a brief remission that may last only a few hours or for a day, followed by more severe symptoms, including:

  • High fever
  • Jaundice (yellow skin)
  • Bleeding
  • Shock
  • Organ failure

Severe yellow fever disease can be deadly (30 – 60% die).

Transmission

Yellow fever virus is transmitted to people through the bite of infected mosquitoes.  It cannot be spread person to person by direct contact.  Mosquitoes acquire the virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates (human or non-human).  Infected persons can transmit yellow fever virus to mosquitoes shortly before the onset of fever and up to 5 days after onset.

Diagnosis

Yellow fever infection is diagnosed based on a person’s symptoms, travel history, and laboratory testing.

Treatment

There is no medicine to treat or cure infection from yellow fever.  Persons with yellow fever should rest, drink fluids, and use pain relievers and medication to reduce fever and relieve aching.  Certain medications, such as aspirin or other nonsteroidal anti-inflammatory drugs (e.g., ibuprofen and naproxen) should be avoided because these may increase the risk of bleeding.

People with severe symptoms of yellow fever infection should be hospitalized for close observation and supportive care.

Immunity

Persons who have been infected with the yellow fever virus are likely to be protected from future infections.

Risk in Hawaii

Prevention

Yellow fever can be prevented by vaccination.

  • Yellow fever vaccine is recommended for people age 9 months or older who are traveling to or living in areas at risk for yellow fever transmission in South America or Africa.
  • Proof of yellow fever vaccination may be required for entry into certain countries. Country-specific yellow fever risk information, along with vaccine recommendations, can be found on the CDC Travelers’ Health Page.

Because of the risk of serious adverse events after yellow fever vaccination, only persons who (1) are at risk of exposure to yellow fever virus, or (2) require proof of vaccination to enter a country should be vaccinated.

For most people, one dose of the vaccine provides long-lasting protection.  Certain travelers may need another dose of the vaccine, either because they have problems with their immune system or they are in higher-risk settings.

In the U.S., yellow fever vaccine is given only at designated yellow fever vaccination centers (see Additional Resources below).

In addition to vaccination, travelers should also take actions to prevent mosquito bites when in areas of Africa or South America with yellow fever transmission.

  • Use insect repellent
    • When you go outdoors, use an EPA-registered insect repellent such as those containing DEET, picaridin, IR3535, or oil of lemon eucalyptus on exposed skin.
  • Wear proper clothing to reduce mosquito bites
    • When weather permits, wear long-sleeves, long pants and socks when outdoors. Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or another EPA-registered repellent will give extra protection.
  • Be aware of peak mosquito hours
    • Peak biting times for many mosquito species is dusk to dawn. However, one of the mosquitoes that transmits yellow fever virus feeds during the daytime.

Additional Resources

Information for Clinicians